I just got a 3-jaw chuck fo my Taig lathe. It comes with two Tommy (?) bars,
a hex key, a washer and a set of instructions. The jaws are aluminium and
unfinished, the instructions tell you how to turn the jaws true.

Before I started I measured the runout using a 1/2" drill rod. It came to
0.006".

I did as the instructions told me. I used the washer provided, chucked it up
at the back of the jaws, made sure it was nice and flat and carefully turned
0.002" off the jaws. The I filed down the little nubbins at the back of the
jaws where the washer was being held during the procedure. I re-measured the
runout: This time it was 0.004". I inspected the jaws: There was evidence of
"clean-up" on all three, the filing seemed satisfactory (I touched up one of
the jaws just to make sure).

I was puzzled by this poor result. I could not think of an explanation. Then
I measured the washer and it turns out to be out of round by 0.004".

I have a number of questions:

1) Is 0.004" TIR satisfactory for a small 3-jaw chuck? I suspect that far
from it but I do not want to be unreasonable.
2) Is the washer the most likely culprit?
3) How to rescue the situation? The obvious solution (assuming the washer is
the culprit) is to find something tthat is perfectly round, chuck it up
again and repeat the procedure. Presumably the object will have to be
thicker than the filed-down portion of the jaws so it is held by the turned
down portion but I may be wrong.
4) What object to use for that purpose? The best I can think right now is to
get a piece of aluminium bar and turn and face it in my 4-jaw chuck and then
part it off at the correct thickness.
5) If one used an object that is too thick or repeated the procedure a few
times the turned down (and hopefully true) portion of the jaws will become
smaller and smaller. What is the minimum size of the gripping portion of the
jaws to provide secure workholding?

Thanks,

--
Michael Koblic
Campbell River, BC

On Fri, 26 Jun 2009 18:11:32 -0700, "Michael Koblic"
wrote:

I was puzzled by this poor result. I could not think of an explanation. Then
I measured the washer and it turns out to be out of round by 0.004".


2) Is the washer the most likely culprit?

Even though the washer is out of round, any three points on its outer
edge define a (perfect) circle. So, unless the washer is so wonky that
one of the jaws wasn't touching it, I don't see how it would make any
difference.

--
Ned Simmons

On Jun 27, 2:11*am, "Michael Koblic" wrote:

1) Is 0.004" TIR satisfactory for a small 3-jaw chuck? I suspect that far
from it but I do not want to be unreasonable.
2) Is the washer the most likely culprit?
3) How to rescue the situation? The obvious solution (assuming the washer is
the culprit) is to find something tthat is perfectly round, chuck it up
again and repeat the procedure. Presumably the object will have to be
thicker than the filed-down portion of the jaws so it is held by the turned
down portion but I may be wrong.
4) What object to use for that purpose? The best I can think right now is to
get a piece of aluminium bar and turn and face it in my 4-jaw chuck and then
part it off at the correct thickness.
5) If one used an object that is too thick or repeated the procedure a few
times the turned down (and hopefully true) portion of the jaws will become
smaller and smaller. What is the minimum size of the gripping portion of the
jaws to provide secure workholding?

Thanks,

--
Michael Koblic
Campbell River, BC

Most of the time .004 TIR is much better than what is needed.
Consider if you hold something by your four jaw chuck and deliberately
have it not centered by say .100. Now without removing the work from
the chuck, you machine the piece until part of it is .500 dia and
another part is .250. And you part it off. The part you machined is
round and the fact that it was not centered exactly when you started
did not make any difference.

Of course if you have to remove the part and then grip it say from the
other end, well that is a different story. Now you have to mark the
part and one jaw so you can put it back so the TIR does not matter.

I think the washer is the culprit. Although the three points that
touch the washer are three points on a circle, the center of that
circle is not on the axis of rotation.

Note that you can turn something perfectly round whether or not it
started out as round or square and this can be done in either a 4 jaw
or your three jaw chuck. So you can make your own washer. Or use a
bolt and a couple of nuts to hold the washer and turn it to be round.

You can make a washer with a large hole, and hold it with your three
jaw chuck touching the hole, not the outside. Then use a boring bar on
the inside of the jaws. That way you do not have to file the little
nibs off. Then check to see what the TIR is. If it is not as good as
you want, then use the washer again and file the little nibs off.

I personally would not try to get the TIR lower, until you try
checking what the TIR is with different sized round things. The TIR
can be perfect at one diameter and off at another if the scroll in the
three jaw chuck is not perfect.


Dan

wrote:
...
I think the washer is the culprit. Although the three points that
touch the washer are three points on a circle, the center of that
circle is not on the axis of rotation. ...

If the center of the circle is not on the axis of rotation, it is
because the jaws are not equal distances from the axis. Otherwise it
will be on the axis, regardless of what's being chucked.

What might not be on the axis is the center of the washer. But the
location of its center is irrelevant.

Bob

"Michael Koblic" wrote in message
...
I just got a 3-jaw chuck fo my Taig lathe. It comes with two Tommy (?)
bars, a hex key, a washer and a set of instructions. The jaws are aluminium
and unfinished, the instructions tell you how to turn the jaws true.

Before I started I measured the runout using a 1/2" drill rod. It came to
0.006".

I did as the instructions told me. I used the washer provided, chucked it
up at the back of the jaws, made sure it was nice and flat and carefully
turned 0.002" off the jaws. The I filed down the little nubbins at the
back of the jaws where the washer was being held during the procedure. I
re-measured the runout: This time it was 0.004". I inspected the jaws:
There was evidence of "clean-up" on all three, the filing seemed
satisfactory (I touched up one of the jaws just to make sure).

I was puzzled by this poor result. I could not think of an explanation.
Then I measured the washer and it turns out to be out of round by 0.004".

I have a number of questions:

1) Is 0.004" TIR satisfactory for a small 3-jaw chuck? I suspect that far
from it but I do not want to be unreasonable.
2) Is the washer the most likely culprit?
3) How to rescue the situation? The obvious solution (assuming the washer
is the culprit) is to find something tthat is perfectly round, chuck it up
again and repeat the procedure. Presumably the object will have to be
thicker than the filed-down portion of the jaws so it is held by the
turned down portion but I may be wrong.
4) What object to use for that purpose? The best I can think right now is
to get a piece of aluminium bar and turn and face it in my 4-jaw chuck and
then part it off at the correct thickness.
5) If one used an object that is too thick or repeated the procedure a few
times the turned down (and hopefully true) portion of the jaws will become
smaller and smaller. What is the minimum size of the gripping portion of
the jaws to provide secure workholding?

Thanks,

--
Michael Koblic
Campbell River, BC
Check runout before removing the washer, should be dead nuts on. Open and
close jaws back on the washer, recheck. The washer has nothing to do with
your runout. The three contact points is true, (as someone else said) no
matter how much runout you have before cutting. When all three jaws are
trimmed, should be .000 runout.

On 2009-06-27, Michael Koblic wrote:
I just got a 3-jaw chuck fo my Taig lathe. It comes with two Tommy (?) bars,
a hex key, a washer and a set of instructions. The jaws are aluminium and
unfinished, the instructions tell you how to turn the jaws true.

Before I started I measured the runout using a 1/2" drill rod. It came to
0.006".

O.K. Did you tighten the screws holding the jaws as you
installed them? Did you press each jaw outward as you tightened the
screws? (Otherwise, they are likely to shift a bit under load.)

The two-piece jaws for larger chucks have both a groove along
the length to keep the top jaws parallel to the master jaws, and a
projection from the master at right angles to the jaws and a matching
cross groove on the underside of the top jaws so they always have the
same length projection -- no depending on the fit of the screws as the
Taig chuck does. (For this reason, on the Taig, I mount the jaws, turn
them to dimension and use them without ever removing them.)

I did as the instructions told me. I used the washer provided, chucked it up
at the back of the jaws, made sure it was nice and flat and carefully turned
0.002" off the jaws. The I filed down the little nubbins at the back of the
jaws where the washer was being held during the procedure.

Hmm ... IIRC, the washer contacts only the hard jaws below the
top (soft) jaws, not the soft jaws so there are no "nubbins" left --
unless you are turning a step to both hold and support a disk-shaped
workpiece.

I re-measured the
runout: This time it was 0.004". I inspected the jaws: There was evidence of
"clean-up" on all three, the filing seemed satisfactory (I touched up one of
the jaws just to make sure).

I was puzzled by this poor result. I could not think of an explanation. Then
I measured the washer and it turns out to be out of round by 0.004".

Not too bad -- depending on the age and quality of the chuck. I
would expect 0.001" or better on a brand new quality chuck (like the
Austrian made chucks for my Compact-5). But those have only one-piece
jaws -- either hardened jaws with steps already made, or soft jaws which
go all the way down to the scroll plate as one piece.

I have a number of questions:

1) Is 0.004" TIR satisfactory for a small 3-jaw chuck? I suspect that far
from it but I do not want to be unreasonable.

First thing is whether there are multiple holes for the tommy
bars. If so, try with each one (using only the master jaws to clamp
with at first) and see which one gives the best concentricity. Then
*mark* that tommy-bar hole in the body so you can always use it for the
final tightening. (In the case of chucks which tighten with keys, if
there are three sockets, one should be marked with a "-0-" or something
similar by the manufacturer. Some have only one socket so there is
never any question.

Mine (an older one) only has tommy bar holes on the scroll
plate, none on the body, so I usually put a Crescent wrench around the
jaws close to the body to hold it from turning when I use the Tommy bar
on the scroll pate.

But once you have bored the jaws to the proper size for the
current workpiece, you should get well under 0.001". It is only when
you move the jaws to grip a different diameter that you can get
significant change in runout -- especially if the scroll plate is not
truly concentric -- or is loose on the projection of the body so it can
shift from side to side as you tighten.

2) Is the washer the most likely culprit?

It could have been a contributing factor -- as could shifting of
the jaws between the truing and the clamping of the test workpiece.

3) How to rescue the situation? The obvious solution (assuming the washer is
the culprit) is to find something tthat is perfectly round, chuck it up
again and repeat the procedure. Presumably the object will have to be
thicker than the filed-down portion of the jaws so it is held by the turned
down portion but I may be wrong.

4) What object to use for that purpose? The best I can think right now is to
get a piece of aluminium bar and turn and face it in my 4-jaw chuck and then
part it off at the correct thickness.

Make it so it will fit behind the soft jaws in contact only with
the master jaws. You may have to unscrew the chuck from the spindle to
get it into place properly.

5) If one used an object that is too thick or repeated the procedure a few
times the turned down (and hopefully true) portion of the jaws will become
smaller and smaller.

Huh? You mean the contact *length* along the faces of the jaws?
Not if you do the clamping only with the master jaws and turn the full
length of the soft jaws. For most things, you *want* the full length of
the soft jaws in contact with the workpiece.

The exception is when you are making soft jaws to hold a disc,
so you turn it true only for a short distance (a little less than the
intended final thickness of the workpiece, so you can face both sides in
the chuck.

And you should have multiple sets of soft jaws. Either buy
more, or machine some aluminum in your small mill (which should be large
enough for this task) to make extra jaws. Make one set for general
purpose -- a stepped set for standard ID gripping, and a reverse stepped
set for larger OD griping. Depending on the precision you need, you can
often get away with turning the existing jaws end-for-end.

Whenever you make a set of jaws, use a number stamp set to mark
the jaws for position 1, 2, or 3, so when you put them back on, they
will be on the same master jaws.

What is the minimum size of the gripping portion of the
jaws to provide secure workholding?

That depends on a lot of things, including the material of the
jaws (aluminum in this case, but hardened steel for hardened top jaws
for larger chucks, or mild steel for soft top jaws for similar sized
chucks. Softer jaws, or softer workpieces need larger contact areas.
And when you are holding a long workpiece and turning some distance from
the chuck jaws, you need the full length of the soft jaws' faces to
minimize tilt in the jaws.

There are other ways to hold the jaws preloaded for turning.
Do web searches and find them.

Good Luck,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

Michael Koblic wrote:
I just got a 3-jaw chuck fo my Taig lathe. It comes with two Tommy (?) bars,
a hex key, a washer and a set of instructions. The jaws are aluminium and
unfinished, the instructions tell you how to turn the jaws true.

Before I started I measured the runout using a 1/2" drill rod. It came to
0.006".

I did as the instructions told me. I used the washer provided, chucked it up
at the back of the jaws, made sure it was nice and flat and carefully turned
0.002" off the jaws. The I filed down the little nubbins at the back of the
jaws where the washer was being held during the procedure. I re-measured the
runout: This time it was 0.004". I inspected the jaws: There was evidence of
"clean-up" on all three, the filing seemed satisfactory (I touched up one of
the jaws just to make sure).

I was puzzled by this poor result. I could not think of an explanation. Then
I measured the washer and it turns out to be out of round by 0.004".

I have a number of questions:

1) Is 0.004" TIR satisfactory for a small 3-jaw chuck? I suspect that far
from it but I do not want to be unreasonable.
2) Is the washer the most likely culprit?
3) How to rescue the situation? The obvious solution (assuming the washer is
the culprit) is to find something tthat is perfectly round, chuck it up
again and repeat the procedure. Presumably the object will have to be
thicker than the filed-down portion of the jaws so it is held by the turned
down portion but I may be wrong.
4) What object to use for that purpose? The best I can think right now is to
get a piece of aluminium bar and turn and face it in my 4-jaw chuck and then
part it off at the correct thickness.
5) If one used an object that is too thick or repeated the procedure a few
times the turned down (and hopefully true) portion of the jaws will become
smaller and smaller. What is the minimum size of the gripping portion of the
jaws to provide secure workholding?

Thanks,



Unless the shaft you are chucking is the same diameter as the washer you
used to cut the jaws, you will get an error caused by the scroll that
moves the jaws in and out.


John

On Jun 27, 2:36*pm, john wrote:
Michael Koblic wrote:

Unless the shaft you are chucking is the same diameter as the washer you
used to cut the jaws, you will get an error caused by the scroll that
moves the jaws in and out.

John

You could stuff the test bar in so it contacts only as much as the
washer did.

Personally the way I use a 3-jaw, all that matters is that the jaws
are parallel when tightened, so the work doesn't wobble. And if it
does anyway, like the stamped head of a bolt, I'll support the end
with the tailstock. You've probably achieved parallelism already
unless the jaws tilted. They shouldn't have if the washer was back
near the scroll.

Plan the job so you can make the finish cuts on all surfaces without
loosening the chuck. It doesn't matter for roughing as long as you
leave an allowance larger than the runout.

I doubt you will ever get the 3-jaw to run true enough that you can
reverse the work and make the cuts from both ends meet invisibly.
That's difficult even with a Set-Tru, 4-jaw or collets, and a good
reason to turn between centers. You could make a gnomon with extra
metal in the ends for the center holes and then part them off later in
the 3-jaw. Or turn to a step or groove from both ends, a little runout
won't show across it.

jsw

DoN. Nichols wrote:

O.K. Did you tighten the screws holding the jaws as you
installed them? Did you press each jaw outward as you tightened the
screws? (Otherwise, they are likely to shift a bit under load.)

They were tight already.

[...]

Hmm ... IIRC, the washer contacts only the hard jaws below the
top (soft) jaws, not the soft jaws so there are no "nubbins" left --
unless you are turning a step to both hold and support a disk-shaped
workpiece.

No. The soft jaws cover the whole thing. There are nubbins...

I was puzzled by this poor result. I could not think of an
explanation. Then I measured the washer and it turns out to be out
of round by 0.004".

Not too bad -- depending on the age and quality of the chuck. I
would expect 0.001" or better on a brand new quality chuck (like the
Austrian made chucks for my Compact-5). But those have only one-piece
jaws -- either hardened jaws with steps already made, or soft jaws
which go all the way down to the scroll plate as one piece.

This a is a US-made new Taig chuck.

First thing is whether there are multiple holes for the tommy
bars. If so, try with each one (using only the master jaws to clamp
with at first) and see which one gives the best concentricity. Then
*mark* that tommy-bar hole in the body so you can always use it for
the final tightening. (In the case of chucks which tighten with
keys, if there are three sockets, one should be marked with a "-0-"
or something similar by the manufacturer. Some have only one socket
so there is never any question.

There are three pairs of holes. I did play with them but it did not seem to
make any difference.

But once you have bored the jaws to the proper size for the
current workpiece, you should get well under 0.001". It is only when
you move the jaws to grip a different diameter that you can get
significant change in runout -- especially if the scroll plate is not
truly concentric -- or is loose on the projection of the body so it
can shift from side to side as you tighten.

This is seems to be the recurring motif. I did not appreciate that this is a
feature of scroll chucks.

4) What object to use for that purpose? The best I can think right
now is to get a piece of aluminium bar and turn and face it in my
4-jaw chuck and then part it off at the correct thickness.

Make it so it will fit behind the soft jaws in contact only with
the master jaws. You may have to unscrew the chuck from the spindle
to get it into place properly.

Not possible. See above.

5) If one used an object that is too thick or repeated the procedure
a few times the turned down (and hopefully true) portion of the jaws
will become smaller and smaller.

Huh? You mean the contact *length* along the faces of the jaws?
Not if you do the clamping only with the master jaws and turn the full
length of the soft jaws. For most things, you *want* the full length
of the soft jaws in contact with the workpiece.

Again, not possible.

And you should have multiple sets of soft jaws. Either buy
more, or machine some aluminum in your small mill (which should be
large enough for this task) to make extra jaws. Make one set for
general purpose -- a stepped set for standard ID gripping, and a
reverse stepped set for larger OD griping. Depending on the
precision you need, you can often get away with turning the existing
jaws end-for-end.

Done that. Mainly on account of being sure that I would roger the first set
of jaws and would need the spare. I was not going to touch anything though
until I understood the current problem.

Whenever you make a set of jaws, use a number stamp set to mark
the jaws for position 1, 2, or 3, so when you put them back on, they
will be on the same master jaws.

Right.


What is the minimum size of the gripping
portion of the jaws to provide secure workholding?

That depends on a lot of things, including the material of the
jaws (aluminum in this case, but hardened steel for hardened top jaws
for larger chucks, or mild steel for soft top jaws for similar sized
chucks. Softer jaws, or softer workpieces need larger contact areas.
And when you are holding a long workpiece and turning some distance
from the chuck jaws, you need the full length of the soft jaws' faces
to minimize tilt in the jaws.

OK. Bigger is better.

There are other ways to hold the jaws preloaded for turning.
Do web searches and find them.

Not too sure that I understand what that means. I shall hit the books.

Thanks,

--
Michael Koblic
Campbell River, BC

Jim Wilkins wrote:
On Jun 27, 2:36 pm, john wrote:
Michael Koblic wrote:

Unless the shaft you are chucking is the same diameter as the washer
you used to cut the jaws, you will get an error caused by the scroll
that moves the jaws in and out.

John

You could stuff the test bar in so it contacts only as much as the
washer did.

Personally the way I use a 3-jaw, all that matters is that the jaws
are parallel when tightened, so the work doesn't wobble. And if it
does anyway, like the stamped head of a bolt, I'll support the end
with the tailstock. You've probably achieved parallelism already
unless the jaws tilted. They shouldn't have if the washer was back
near the scroll.

Plan the job so you can make the finish cuts on all surfaces without
loosening the chuck. It doesn't matter for roughing as long as you
leave an allowance larger than the runout.

I doubt you will ever get the 3-jaw to run true enough that you can
reverse the work and make the cuts from both ends meet invisibly.
That's difficult even with a Set-Tru, 4-jaw or collets, and a good
reason to turn between centers. You could make a gnomon with extra
metal in the ends for the center holes and then part them off later in
the 3-jaw. Or turn to a step or groove from both ends, a little runout
won't show across it.


Thank you and all the others.

The critical bit of information seems to be that 3-jaw scroll chucks do not
necessarily hold true at all diameters thus trying to improve on the 4 thou
of runout would probably put me on the flat portion of the diminishing
return curve.

I am not set up for turning between centres yet - that comes next and will
invove cobbling some sort of centre for the headstock and a dog (apparently
the cognoscenti like a hose clip for this). This will invove turning things
to a point so a compound slide will be in order. Another issue is facing off
longish cylinders (the inner diameter of the spindle is only 5/16") and I
shall be needing a steady rest.

But all of that had to be put on hold as I have not had a decent arrangement
to grind lathe bits. I finally finished it today.

This is worse than having a baby.

I wonder at what point one returns to some semblance of productive work
rather just continue making tools for tools...:-) It has become a running
joke in the family.

--
Michael Koblic
Campbell River, BC

Michael Koblic wrote:
I just got a 3-jaw chuck fo my Taig lathe. It comes with two Tommy (?) bars,
a hex key, a washer and a set of instructions. The jaws are aluminium and
unfinished, the instructions tell you how to turn the jaws true.

Before I started I measured the runout using a 1/2" drill rod. It came to
0.006".

I did as the instructions told me. I used the washer provided, chucked it up
at the back of the jaws, made sure it was nice and flat and carefully turned
0.002" off the jaws. The I filed down the little nubbins at the back of the
jaws where the washer was being held during the procedure. I re-measured the
runout: This time it was 0.004". I inspected the jaws: There was evidence of
"clean-up" on all three, the filing seemed satisfactory (I touched up one of
the jaws just to make sure).

I was puzzled by this poor result. I could not think of an explanation. Then
I measured the washer and it turns out to be out of round by 0.004".

I have a number of questions:

1) Is 0.004" TIR satisfactory for a small 3-jaw chuck? I suspect that far
from it but I do not want to be unreasonable.
2) Is the washer the most likely culprit?
3) How to rescue the situation? The obvious solution (assuming the washer is
the culprit) is to find something tthat is perfectly round, chuck it up
again and repeat the procedure. Presumably the object will have to be
thicker than the filed-down portion of the jaws so it is held by the turned
down portion but I may be wrong.
4) What object to use for that purpose? The best I can think right now is to
get a piece of aluminium bar and turn and face it in my 4-jaw chuck and then
part it off at the correct thickness.
5) If one used an object that is too thick or repeated the procedure a few
times the turned down (and hopefully true) portion of the jaws will become
smaller and smaller. What is the minimum size of the gripping portion of the
jaws to provide secure workholding?

Thanks,


Not sure about the construction of the TAIG chuck and how it operates
given the mention of a tommy bar and looking at the TAIG site but all
the 3 jaw self centering chucks I have are marked with a master pinion
which gives the least run-out when used. The chucks I have all have 3
pinions which operate the scroll and one produces the least run-out. As
the TAIG is a scroll chuck, from what I read, then if you have more than
one hole for the tommy bar to tighten the chuck, then maybe you want to
mark and always use the same hole to ensure consistancy, that may
improve you run-out. Maybe also tighten using different tommy bar holes
and see which produce the least run-out.

On 2009-06-28, Michael Koblic wrote:
DoN. Nichols wrote:

O.K. Did you tighten the screws holding the jaws as you
installed them? Did you press each jaw outward as you tightened the
screws? (Otherwise, they are likely to shift a bit under load.)

They were tight already.

Tight -- but perhaps not preloaded when tightening. There is
some slop in the screws fit into the soft jaws which can allow them to
shift if you don't pre-load the jaws towards the outer diameter while
you (or the factory) are tightening the screws.

[...]

Hmm ... IIRC, the washer contacts only the hard jaws below the
top (soft) jaws, not the soft jaws so there are no "nubbins" left --
unless you are turning a step to both hold and support a disk-shaped
workpiece.

No. The soft jaws cover the whole thing. There are nubbins...

O.K. Take the chuck off the lathe.

Adjust the jaws to the point where the hard "master" jaws are
level with the OD of the chuck body. The soft jaws will stick out
beyond that point.

Now -- using a small flashlight, look in through the threaded
aperture in the back which screws onto the lathe's spindle. You should
see the ends of the master jaws sticking out about 1/16" or a bit more.
Past those you will see the soft jaws closing to about the right size
to hold a 1/16" diameter workpiece (minus what you have removed in
truing the jaws).

Now -- turn something (a plug) which will just barely slip in
past the threads, and about the length of the master jaws. Close the
*master* jaws tightly onto that, and re-mount the chuck on the lathe
spindle.

Now -- use a drill bit to slightly enlarge the hole in the
center where the soft jaws almost meet -- and then use a boring tool to
reach down through there and enlarge the hole a little. If you intend
to hold something of a known diameter, drill a little undersized for
that and then bore to barely fit that. Then loosen the jaws, remove the
plug which held the jaws pre-loaded, and tighten the jaws onto your
workpiece. If you are going to hold a disk instead of a shaft which
will fit through, bore to leave about 1/2" of the jaws near the body
(which should clear the screws which mount the jaws), and to the
diameter of the disk to be held.

I was puzzled by this poor result. I could not think of an
explanation. Then I measured the washer and it turns out to be out
of round by 0.004".

Not too bad -- depending on the age and quality of the chuck. I
would expect 0.001" or better on a brand new quality chuck (like the
Austrian made chucks for my Compact-5). But those have only one-piece
jaws -- either hardened jaws with steps already made, or soft jaws
which go all the way down to the scroll plate as one piece.

This a is a US-made new Taig chuck.

I thought so, but I was writing for more than just you. Note
that I covered "quality" above as well -- The Austrian chucks for my
Compact-5 sold for more than your Taig cost complete with both chucks.
Each one comes with a certificate of accuracy -- when brand new, and my
examples were more accurate than the certificate promised.

First thing is whether there are multiple holes for the tommy
bars. If so, try with each one (using only the master jaws to clamp
with at first) and see which one gives the best concentricity. Then
*mark* that tommy-bar hole in the body so you can always use it for
the final tightening. (In the case of chucks which tighten with
keys, if there are three sockets, one should be marked with a "-0-"
or something similar by the manufacturer. Some have only one socket
so there is never any question.

There are three pairs of holes. I did play with them but it did not seem to
make any difference.

Hmm ... you don't really want to call them pairs, since
depending on the size of the workpiece, any one of the scroll plate
holes may be used with any one of the body holes. And the hole which
matters is the body hole (which mine does not have), not the scroll
plate hole. You use the scroll plate hole which is the closest upstream
from the preferred body hole as the jaws just start to touch.

But once you have bored the jaws to the proper size for the
current workpiece, you should get well under 0.001". It is only when
you move the jaws to grip a different diameter that you can get
significant change in runout -- especially if the scroll plate is not
truly concentric -- or is loose on the projection of the body so it
can shift from side to side as you tighten.

This is seems to be the recurring motif. I did not appreciate that this is a
feature of scroll chucks.

A scroll-backed (universal) chuck is mostly for quick setup
where the concentricity is not too critical -- e.g. when you are going
to turn all the features in one setup and then part off from what is
held in the chuck.

If you want *precision*, you take the time with an independent
4-jaw chuck to do the setup with a sensitive dial runout indicator.

But another use for a 3-jaw is with either reversed jaws
(assuming one-piece chuck jaws), or with soft jaws turned to make
reversed steps to hold a larger diameter disk shaped object. If you
want to handle even larger, make a set of extra-long soft jaws for the
3-jaw you have and bore them to a close fit so you can clamp the jaws
onto the workpiece with very little motion of the scroll plate. You
don't really need precision centering for this, because you will be
using it to face the workpiece not to turn the OD.

You can also reverse the jaws on your 4-jaw chuck, so the jaws
look somewhat like this (use a fixed-pitch font like Courier to avoid
*serious* distortion of the image):

+--------+ +--------+
| | | | | |
| | +---------+ +---------+ | |
| | | | | |
| | Jaw #1 +---------+ +---------+ Jaw #3 | |
| | | | | |
|____________________________| |____________________________|
+---------------------------------+ +---------------------------------+
| Chuck Body | | |
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~.......~~~~~~~~ ~~~~~~~~~~~~~~~~~~~~~~~~~~~

so you can grip larger diameter stock -- though not as large as you can
with the 3-jaw with custom soft jaws. Just be careful that the custom
soft jaws are not so long that they will hit the bed.

4) What object to use for that purpose? The best I can think right
now is to get a piece of aluminium bar and turn and face it in my
4-jaw chuck and then part it off at the correct thickness.

Make it so it will fit behind the soft jaws in contact only with
the master jaws. You may have to unscrew the chuck from the spindle
to get it into place properly.

Not possible. See above.

See description above. The preload filler contacts the hard
master jaws, not the soft jaws which you are turning to true them up.
(Preload because it holds the master jaws in contact with the scroll
plate the way they will be in normal use.) Note that the advice which
you got in one of the other followups yesterday, which suggested a large
ring and backing the jaws out against that is not good for when you are
trying to true the jaws for normal gripping, as it preloads against the
wrong face of the scroll and the jaws' matching teeth. However, it is
*good* advice if you are turning the OD of the jaws, or turning steps on
the jaws to grip the ID of a workpiece, since in this case the jaws and
the scroll plate will be preloaded in the direction in which they will
be used.

Note that if you want real repeatable precision, you want
collets, and the good collets for a Taig spindle (not the standard one,
but the special one) are the WW style drawbar collets, which are size
limited -- 3/16" max for pass-through, and 1/4" for short gripped stock.

The standard collets which come with the lathe will handle
larger workpieces, but are not as precise. If you want precision for
anything larger than 1/4" with this lathe, you will have to use the
4-jaw and a good dial runout indicator.

Hmm .... I wonder whether they make an ER-16 or ER-25 collet
nosepiece for this machine?

5) If one used an object that is too thick or repeated the procedure
a few times the turned down (and hopefully true) portion of the jaws
will become smaller and smaller.

Huh? You mean the contact *length* along the faces of the jaws?
Not if you do the clamping only with the master jaws and turn the full
length of the soft jaws. For most things, you *want* the full length
of the soft jaws in contact with the workpiece.

Again, not possible.

Yes -- it *is* possible -- if you follow my suggestion at the
top of this for a plug for preloading the *master* jaws while you are
turning the soft jaws.

And you should have multiple sets of soft jaws. Either buy
more, or machine some aluminum in your small mill (which should be
large enough for this task) to make extra jaws. Make one set for
general purpose -- a stepped set for standard ID gripping, and a
reverse stepped set for larger OD griping. Depending on the
precision you need, you can often get away with turning the existing
jaws end-for-end.

Done that. Mainly on account of being sure that I would roger the first set
of jaws and would need the spare. I was not going to touch anything though
until I understood the current problem.

:-)

Remember that you can also *make* new soft jaws -- use an
unmodified set as a pattern -- and you can make them over-long to grip
larger diameter disk workpieces.

Whenever you make a set of jaws, use a number stamp set to mark
the jaws for position 1, 2, or 3, so when you put them back on, they
will be on the same master jaws.

Right.

And if there are no markings beside the jaws on the chuck body
(there are none on mine) use the same number stamps to mark the jaw
ways, starting with a randomly picked jaw as 1, and increasing as you
move in the direction that you turn the scroll plate to tighten the
jaws. Note that you will not be able to stamp the master jaws -- they
are too hard. But at least my chuck won't turn far enough to take the
master jaws out -- you need to remove the circlip on the back and
withdraw the scroll plate to do this -- and you should not need to do
so.

O.K. Now there *are* markings -- I went down to do that while
verifying the capacity of the WW series collets. I used 1/16" number
stamps which are a bit small, but are certain to fit on a part of the
side of the soft jaw which is not likely to be turned off.


What is the minimum size of the gripping
portion of the jaws to provide secure workholding?

That depends on a lot of things, including the material of the
jaws (aluminum in this case, but hardened steel for hardened top jaws
for larger chucks, or mild steel for soft top jaws for similar sized
chucks. Softer jaws, or softer workpieces need larger contact areas.
And when you are holding a long workpiece and turning some distance
from the chuck jaws, you need the full length of the soft jaws' faces
to minimize tilt in the jaws.

OK. Bigger is better.

There are other ways to hold the jaws preloaded for turning.
Do web searches and find them.

Not too sure that I understand what that means. I shall hit the books.

Instead of tightening the jaws -- or the master jaws as I have
suggested above -- onto a washer or a plug, you can do other things:

1) Put three pieces of the same thickness between the angled faces
of the jaws as you close it. I would suggest 3/16" or 1/4" HSS
tool bits, as they tend to be rather precise in dimensions.

2) Drill three holes to form an equilateral triangle around a
large center hole, tap for screws (say #10 or maybe 1/4") and
place those screws so they project into the holes for the heads
of the screws which hold the soft jaws to the master jaws.
Place these into the holes and tighten the jaws. You may want
to make it with several sets of screw holes for different jaw
positions. You bore the jaws through the center hole.

3) Three larger holes in a triangle with a center hole bored to
intersect the three so the tips of the jaws stick through for
turning while the holes' walls press on the angled faces of the
jaws while you are turning.

I hope that this helps.
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2009-06-28, Michael Koblic wrote:
Jim Wilkins wrote:

[ ... ]

Plan the job so you can make the finish cuts on all surfaces without
loosening the chuck. It doesn't matter for roughing as long as you
leave an allowance larger than the runout.

Very good advice.

I doubt you will ever get the 3-jaw to run true enough that you can
reverse the work and make the cuts from both ends meet invisibly.
That's difficult even with a Set-Tru, 4-jaw or collets, and a good
reason to turn between centers. You could make a gnomon with extra
metal in the ends for the center holes and then part them off later in
the 3-jaw. Or turn to a step or groove from both ends, a little runout
won't show across it.


Thank you and all the others.

The critical bit of information seems to be that 3-jaw scroll chucks do not
necessarily hold true at all diameters thus trying to improve on the 4 thou
of runout would probably put me on the flat portion of the diminishing
return curve.

Yes. How close to 0.001" you get is a function of how much you
spend for the chuck -- and the precision of the lathe spindle setup too.
The Taig is likely to shift a bit every time you remove and replace the
chuck. Try it with a piece chucked up and see what happens.

I am not set up for turning between centres yet - that comes next and will
invove cobbling some sort of centre for the headstock and a dog (apparently
the cognoscenti like a hose clip for this).

Interesting -- but I guess that it will work. For the Taig, I
use a small dog which came with my Unimat SL-1000.

This will invove turning things
to a point so a compound slide will be in order.

Also -- ideally, you will want a live (ball bearing) center for
the tailstock end. That way you don't have to keep lubricating the
center.

Another issue is facing off
longish cylinders (the inner diameter of the spindle is only 5/16") and I
shall be needing a steady rest.

Yes -- you will.

But all of that had to be put on hold as I have not had a decent arrangement
to grind lathe bits. I finally finished it today.

:-)

This is worse than having a baby.

:-)

I wonder at what point one returns to some semblance of productive work
rather just continue making tools for tools...:-) It has become a running
joke in the family.

The primary purpose of *any* home shop is to make tools for the
tools. Any actual products other than this are a matter of luck -- or
testing the tools which you made. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2009-06-28, David Billington wrote:
Michael Koblic wrote:
I just got a 3-jaw chuck fo my Taig lathe. It comes with two Tommy (?) bars,
a hex key, a washer and a set of instructions. The jaws are aluminium and
unfinished, the instructions tell you how to turn the jaws true.

[ ... ]

Not sure about the construction of the TAIG chuck and how it operates
given the mention of a tommy bar and looking at the TAIG site but all
the 3 jaw self centering chucks I have are marked with a master pinion
which gives the least run-out when used.

No pinions on the Taig 3-jaw. The scroll plate is bare on the
back of the chuck, with three holes for Tommy bars drilled in its edge
for tommy bars. The chuck body (thin compared to one for pinions) may
also have three holes for Tommy bars. (Mine is an old one, and does not
have the holes in the body, so I have to grip the jaws. :-)

The chucks I have all have 3
pinions which operate the scroll and one produces the least run-out. As
the TAIG is a scroll chuck, from what I read, then if you have more than
one hole for the tommy bar to tighten the chuck, then maybe you want to
mark and always use the same hole to ensure consistancy, that may
improve you run-out.

Actually -- the closest approximation of the "same pinion" in
the Taig is the same hole in the chuck body. The scroll plate should
use the nearest hole approaching the master hole in the body to maintain
an approximation of the same pinion effect.

The chuck has two-piece jaws, with the master jaws being
hardened, and captive unless you remove the snap-ring and scroll plate
(which should be avoided unless necessary). The top jaws are
aluminum, with a groove to maintain alignment with the master jaws, but
without a cross-groove to maintain the position of the soft jaws along
the master. They depend on the fit of the screws which secure the top
jaws and nothing else.

Maybe also tighten using different tommy bar holes
and see which produce the least run-out.

Yes -- pay particular attention to which tommy bar hole in the
body gives the most consistent runout. It will be more sensitive to
that than to the tommy-bar hole in the scroll plate.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On 2009-06-29, DoN. Nichols wrote:
On 2009-06-28, Michael Koblic wrote:
DoN. Nichols wrote:

[ ... ]

A scroll-backed (universal) chuck is mostly for quick setup
where the concentricity is not too critical -- e.g. when you are going
to turn all the features in one setup and then part off from what is
held in the chuck.

If you want *precision*, you take the time with an independent
4-jaw chuck to do the setup with a sensitive dial runout indicator.

But another use for a 3-jaw is with either reversed jaws
(assuming one-piece chuck jaws), or with soft jaws turned to make
reversed steps to hold a larger diameter disk shaped object. If you
want to handle even larger, make a set of extra-long soft jaws for the
3-jaw you have and bore them to a close fit so you can clamp the jaws
onto the workpiece with very little motion of the scroll plate. You
don't really need precision centering for this, because you will be
using it to face the workpiece not to turn the OD.

I saw this today, and bookmarked it to post as relevant to this
part of this thread:

http://www.frets.com/HomeShopTech/Projects/Bison/bison.html

scroll (way) down to where you see:

================================================== ====================
Part Two - Extra Long Soft Jaws
================================================== ====================

(It looks like it is about 2/3 to 3/4 of the way down the web page.)

Anyway -- this is what I was talking about for making the long
soft jaws. You can also see the difference in the way the jaws are made
by comparing the first photo with your jaw. It has more features to
assure alignment. By the end of the page, you can see it being used to
make a disc like what you would use for your sundials.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

"DoN. Nichols" wrote in message
...
I saw this today, and bookmarked it to post as relevant to this
part of this thread:

http://www.frets.com/HomeShopTech/Projects/Bison/bison.html

scroll (way) down to where you see:

================================================== ====================
Part Two - Extra Long Soft Jaws
================================================== ====================

(It looks like it is about 2/3 to 3/4 of the way down the web page.)

Anyway -- this is what I was talking about for making the long
soft jaws. You can also see the difference in the way the jaws are made
by comparing the first photo with your jaw. It has more features to
assure alignment. By the end of the page, you can see it being used to
make a disc like what you would use for your sundials.


This is good stuff! Duly bookmarked, thanks.

--
Michael Koblic
Campbell River, BC

DoN. Nichols wrote:

[...]

O.K. Take the chuck off the lathe.

Adjust the jaws to the point where the hard "master" jaws are
level with the OD of the chuck body. The soft jaws will stick out
beyond that point.

Now -- using a small flashlight, look in through the threaded
aperture in the back which screws onto the lathe's spindle. You
should
see the ends of the master jaws sticking out about 1/16" or a bit
more.
Past those you will see the soft jaws closing to about the right size
to hold a 1/16" diameter workpiece (minus what you have removed in
truing the jaws).

Now -- turn something (a plug) which will just barely slip in
past the threads, and about the length of the master jaws. Close the
*master* jaws tightly onto that, and re-mount the chuck on the lathe
spindle.

Now -- use a drill bit to slightly enlarge the hole in the
center where the soft jaws almost meet -- and then use a boring tool
to reach down through there and enlarge the hole a little. If you
intend
to hold something of a known diameter, drill a little undersized for
that and then bore to barely fit that. Then loosen the jaws, remove
the plug which held the jaws pre-loaded, and tighten the jaws onto
your workpiece. If you are going to hold a disk instead of a shaft
which
will fit through, bore to leave about 1/2" of the jaws near the body
(which should clear the screws which mount the jaws), and to the
diameter of the disk to be held.


OK, I understand the procedure. Clearly this could have been done neither as
per the factory instruction nor using the kit provided.

I am still not clear about the purpose of doing it this way. I understand
the purpose of pre-loading the jaws (as per the info I have found so far) is
to prevent the cant of the jaws outwards at the tips if the workpiece is
inserted only part way.

Let us assume that the soft jaws are loose on the screws attaching them to
the master jaws. If one pre-loads the master jaws as you outlined and then
tries to turn the soft jaws they will not be supported and the cut will be
made in a way that will leave the surfaces in no relationship to what they
would be eventually when tightened on a workpiece. If, however, one follows
the procedure as outlined in the OP, the base of the soft jaws is tight
against the washer. This pressure will push the jaws tight against the
screws and transmit the pressure further to the master jaws which should
thus become pr-loaded in a manner identical to yours. Thus everyhting should
be nice and tight and identical to a workiece with a diameter identical to
the diameter of the washer being held in the jaws. The jaws are fixed and
turning will remove the material form the right places.


[...]

Hmm ... you don't really want to call them pairs, since
depending on the size of the workpiece, any one of the scroll plate
holes may be used with any one of the body holes. And the hole which
matters is the body hole (which mine does not have), not the scroll
plate hole. You use the scroll plate hole which is the closest
upstream from the preferred body hole as the jaws just start to touch.


I went back to this coincidentally this afternoon before reading your post
and quickly realized that this is the case. The reason I did not get any
helpful result before is that I did not appreciate the difference between
the holes. In fact after correcting for this I could get the run out as
little as 0.001" using a specific hole on the body which is now clearly
marked. Problem solved!

[...]

If you want *precision*, you take the time with an independent
4-jaw chuck to do the setup with a sensitive dial runout indicator.


You also feel the death approaching that much more quickly...

But another use for a 3-jaw is with either reversed jaws
(assuming one-piece chuck jaws), or with soft jaws turned to make
reversed steps to hold a larger diameter disk shaped object. If you
want to handle even larger, make a set of extra-long soft jaws for the
3-jaw you have and bore them to a close fit so you can clamp the jaws
onto the workpiece with very little motion of the scroll plate. You
don't really need precision centering for this, because you will be
using it to face the workpiece not to turn the OD.

Holding large objects is one thing, turning them is another. I do not care
for the noise the little fella makes when I order him to do this.

You can also reverse the jaws on your 4-jaw chuck,

[...]

I did that and then turned and faced a 4.5" washer. The bottom cleared the
ways by about 1/8" and getting to the side of the disk was a little tricky.
Not to mention doing it at 575 rpm...

[...]

See description above. The preload filler contacts the hard
master jaws, not the soft jaws which you are turning to true them up.
(Preload because it holds the master jaws in contact with the scroll
plate the way they will be in normal use.) Note that the advice which
you got in one of the other followups yesterday, which suggested a
large ring and backing the jaws out against that is not good for when
you are trying to true the jaws for normal gripping, as it preloads
against the wrong face of the scroll and the jaws' matching teeth.
However, it is *good* advice if you are turning the OD of the jaws,
or turning steps on
the jaws to grip the ID of a workpiece, since in this case the jaws
and
the scroll plate will be preloaded in the direction in which they will
be used.

I started up on that. Inadvertently. The first parting tool I made just did
not cut it. It spun the toolpost and shaved the jaws before I realized what
was going on.

But the advice on turning the OD jaws is noted. I also found some good stuff
he
http://www.ctemag.com/pdf/2002/0203-topchoices.pdf

related to what the shape of the jaws should be etc.

[...]

And if there are no markings beside the jaws on the chuck body
(there are none on mine) use the same number stamps to mark the jaw
ways, starting with a randomly picked jaw as 1, and increasing as you
move in the direction that you turn the scroll plate to tighten the
jaws. Note that you will not be able to stamp the master jaws -- they
are too hard. But at least my chuck won't turn far enough to take the
master jaws out -- you need to remove the circlip on the back and
withdraw the scroll plate to do this -- and you should not need to do
so.

Scratching has worked well so far. Engraving also a possibility.

[...]

1) Put three pieces of the same thickness between the angled faces
of the jaws as you close it. I would suggest 3/16" or 1/4" HSS
tool bits, as they tend to be rather precise in dimensions.

2) Drill three holes to form an equilateral triangle around a
large center hole, tap for screws (say #10 or maybe 1/4") and
place those screws so they project into the holes for the heads
of the screws which hold the soft jaws to the master jaws.
Place these into the holes and tighten the jaws. You may want
to make it with several sets of screw holes for different jaw
positions. You bore the jaws through the center hole.

3) Three larger holes in a triangle with a center hole bored to
intersect the three so the tips of the jaws stick through for
turning while the holes' walls press on the angled faces of the
jaws while you are turning.

I hope that this helps.

No. My head just exploded.
OTOH the second (re-worked) parting tool works just fine. Once you get past
the squealing and screeching of the bigger OD down to about 3/8" :-)
Gotta stay positive...

--
Michael Koblic
Campbell River, BC

DoN. Nichols wrote:

[...]

This will invove turning
things to a point so a compound slide will be in order.

Also -- ideally, you will want a live (ball bearing) center for
the tailstock end. That way you don't have to keep lubricating the
center.

Did I not mention it? It is on my Lee Valley wish list...

Another issue is
facing off longish cylinders (the inner diameter of the spindle is
only 5/16") and I shall be needing a steady rest.

Yes -- you will.

But all of that had to be put on hold as I have not had a decent
arrangement to grind lathe bits. I finally finished it today.

It nearly burned down today. See my other post.

[...]

The primary purpose of *any* home shop is to make tools for the
tools. Any actual products other than this are a matter of luck -- or
testing the tools which you made. :-)

When I look at the list of things that are needed and compare it with the
work rate so far it is clear that this year will be written off unless I
start throwing money at the various issues. OTOH that would be nowhere near
as educational...

--
Michael Koblic
Campbell River, BC

On 2009-06-30, Michael Koblic wrote:
DoN. Nichols wrote:

[...]

O.K. Take the chuck off the lathe.

Adjust the jaws to the point where the hard "master" jaws are
level with the OD of the chuck body. The soft jaws will stick out
beyond that point.

Now -- using a small flashlight, look in through the threaded
aperture in the back which screws onto the lathe's spindle. You
should
see the ends of the master jaws sticking out about 1/16" or a bit
more.
Past those you will see the soft jaws closing to about the right size
to hold a 1/16" diameter workpiece (minus what you have removed in
truing the jaws).

Now -- turn something (a plug) which will just barely slip in
past the threads, and about the length of the master jaws. Close the
*master* jaws tightly onto that, and re-mount the chuck on the lathe
spindle.

Now -- use a drill bit to slightly enlarge the hole in the
center where the soft jaws almost meet -- and then use a boring tool
to reach down through there and enlarge the hole a little. If you
intend
to hold something of a known diameter, drill a little undersized for
that and then bore to barely fit that. Then loosen the jaws, remove
the plug which held the jaws pre-loaded, and tighten the jaws onto
your workpiece. If you are going to hold a disk instead of a shaft
which
will fit through, bore to leave about 1/2" of the jaws near the body
(which should clear the screws which mount the jaws), and to the
diameter of the disk to be held.


OK, I understand the procedure. Clearly this could have been done neither as
per the factory instruction nor using the kit provided.

Well ... it would have been possible to put the washer in there
behind the soft jaws and in contact with the master jaws.

I am still not clear about the purpose of doing it this way. I understand
the purpose of pre-loading the jaws (as per the info I have found so far) is
to prevent the cant of the jaws outwards at the tips if the workpiece is
inserted only part way.

That depend in part on the rigidity of the chuck and the jaws.
Your top jaws are aluminum, so they will give more with given force than
the steel ones will.

Let us assume that the soft jaws are loose on the screws attaching them to
the master jaws.

Then first tighten them somewhat onto a cylindrical part, and
then tighten the screws mostly. Then tighten a bit harder onto the
cylindrical part, and firmly tighten down the screws the rest of the
way. (I guess that I should suggest a torque limit, but do you have a
torque wrench which measures in inch pounds anyway?) I typically go by
the spring of the Allen key's handle as an indication of torque.

If one pre-loads the master jaws as you outlined and then
tries to turn the soft jaws they will not be supported and the cut will be
made in a way that will leave the surfaces in no relationship to what they
would be eventually when tightened on a workpiece.

Right -- which is why the first step is to make sure the jaw's
screws are tightened while the jaws are preloaded as above.

If, however, one follows
the procedure as outlined in the OP, the base of the soft jaws is tight
against the washer. This pressure will push the jaws tight against the
screws and transmit the pressure further to the master jaws which should
thus become pr-loaded in a manner identical to yours. Thus everyhting should
be nice and tight and identical to a workiece with a diameter identical to
the diameter of the washer being held in the jaws. The jaws are fixed and
turning will remove the material form the right places.

Ans as soon as you loosen the chuck to remove the washer, you
also let the jaws shift, because you did not take pains to tighten the
jaws' screws under preload first. :-)

[ ... ]

Hmm ... you don't really want to call them pairs, since
depending on the size of the workpiece, any one of the scroll plate
holes may be used with any one of the body holes. And the hole which
matters is the body hole (which mine does not have), not the scroll
plate hole. You use the scroll plate hole which is the closest
upstream from the preferred body hole as the jaws just start to touch.


I went back to this coincidentally this afternoon before reading your post
and quickly realized that this is the case.

Good!

The reason I did not get any
helpful result before is that I did not appreciate the difference between
the holes. In fact after correcting for this I could get the run out as
little as 0.001" using a specific hole on the body which is now clearly
marked. Problem solved!

Great!

[...]

If you want *precision*, you take the time with an independent
4-jaw chuck to do the setup with a sensitive dial runout indicator.


You also feel the death approaching that much more quickly...

Nope -- you are too busy setting things up to notice that. :-)

But another use for a 3-jaw is with either reversed jaws
(assuming one-piece chuck jaws), or with soft jaws turned to make
reversed steps to hold a larger diameter disk shaped object. If you
want to handle even larger, make a set of extra-long soft jaws for the
3-jaw you have and bore them to a close fit so you can clamp the jaws
onto the workpiece with very little motion of the scroll plate. You
don't really need precision centering for this, because you will be
using it to face the workpiece not to turn the OD.

Holding large objects is one thing, turning them is another. I do not care
for the noise the little fella makes when I order him to do this.

Keep the extension of everything you can as short as possible.

You can also reverse the jaws on your 4-jaw chuck,

[...]

I did that and then turned and faced a 4.5" washer. The bottom cleared the
ways by about 1/8" and getting to the side of the disk was a little tricky.

That is what the soft jaws are for. If the washer (or other
disc) is thinner than the steps of the jaws on the 4-jaw, you take a new
set of soft jaws for the 3-jaw, and turn them (after preloading) to a
step just deep enough to allow facing both sides. You can actually
make it a little deeper, and just expect to machine off a bit of the
height of the soft jaws as you do the first workpiece. Remember -- the
parts of the soft jaws are expendable. :-)

Not to mention doing it at 575 rpm...

I would swear that mine will go slower than that. How many belt
steps are on your pulleys?

And you could replace the motor with a three phase or a DC motor
and connect an appropriate controller to it to get speeds perhaps 1/6th
your current speed. That would take you down to 100 RPM or a bit
slower. My 12" Clausing will go down to 210 RPM in direct drive, and if
I engage the back gear, it will go down to 35 RPM. The corresponding
highest speeds are 1600 RPM and 270 RPM. Having a variable speed motor
would be somewhat the equivalent of having a back gear -- except that it
would not boost the torque the way a back gear does.

[...]

See description above. The preload filler contacts the hard
master jaws, not the soft jaws which you are turning to true them up.
(Preload because it holds the master jaws in contact with the scroll
plate the way they will be in normal use.) Note that the advice which
you got in one of the other followups yesterday, which suggested a
large ring and backing the jaws out against that is not good for when
you are trying to true the jaws for normal gripping, as it preloads
against the wrong face of the scroll and the jaws' matching teeth.
However, it is *good* advice if you are turning the OD of the jaws,
or turning steps on
the jaws to grip the ID of a workpiece, since in this case the jaws
and
the scroll plate will be preloaded in the direction in which they will
be used.

I started up on that. Inadvertently. The first parting tool I made just did
not cut it. It spun the toolpost and shaved the jaws before I realized what
was going on.

Clamp some heavy paper between the toolpost and the table or
compound and it will increase the holding power by fitting into

But the advice on turning the OD jaws is noted. I also found some good stuff
he
http://www.ctemag.com/pdf/2002/0203-topchoices.pdf

related to what the shape of the jaws should be etc.

Of course, this is written from the perspective of someone who
is after 0.0001" runout -- and is working with a machine capable of
that. :-)

But it does have good information -- including the ring and pins
in the jaws' mounting holes which is shown in the first photograph. It
looks as though the pins are a permanent part -- under the heads of the
outer bolts holding the top (soft) jaws to the master jaws.

[...]

And if there are no markings beside the jaws on the chuck body
(there are none on mine) use the same number stamps to mark the jaw
ways, starting with a randomly picked jaw as 1, and increasing as you
move in the direction that you turn the scroll plate to tighten the
jaws. Note that you will not be able to stamp the master jaws -- they
are too hard. But at least my chuck won't turn far enough to take the
master jaws out -- you need to remove the circlip on the back and
withdraw the scroll plate to do this -- and you should not need to do
so.

Scratching has worked well so far. Engraving also a possibility.

O.K. Be sure to use surfaces which are not critical -- perhaps
the outer ends of the master jaws. A carbide-tipped vibrating engraver
(Burgess Vibrograver or equivalent) will probably do.

[...]

1) Put three pieces of the same thickness between the angled faces
of the jaws as you close it. I would suggest 3/16" or 1/4" HSS
tool bits, as they tend to be rather precise in dimensions.

2) Drill three holes to form an equilateral triangle around a
large center hole, tap for screws (say #10 or maybe 1/4") and
place those screws so they project into the holes for the heads
of the screws which hold the soft jaws to the master jaws.
Place these into the holes and tighten the jaws. You may want
to make it with several sets of screw holes for different jaw
positions. You bore the jaws through the center hole.

3) Three larger holes in a triangle with a center hole bored to
intersect the three so the tips of the jaws stick through for
turning while the holes' walls press on the angled faces of the
jaws while you are turning.

I hope that this helps.

No. My head just exploded.

Those are not all used at the same time. They are three
different ways to preload the jaws without getting in the way of the
boring operation. It helps to find the web pages illustrating the
techniques. I've seen (1) and (3) above illustrated in web pages.

OTOH the second (re-worked) parting tool works just fine. Once you get past
the squealing and screeching of the bigger OD down to about 3/8" :-)

Keeping the amount or projection down to a minimum helps a lot.
Making sure that the sides of the parting tool are parallel and
perpendicular to the axis of the workpiece helps. Having the parting
happening as close to the chuck's jaws as possible helps. Getting
lubricant to the bottom of the groove helps. And ideally, not having a
compound as part of the stackup will help minimize the flex of the
system.

Gotta stay positive...

Yep!

Enjoy,
DoN.

--
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--- Black Holes are where God is dividing by zero ---

On 2009-06-30, Michael Koblic wrote:
DoN. Nichols wrote:

[...]

This will invove turning
things to a point so a compound slide will be in order.

Also -- ideally, you will want a live (ball bearing) center for
the tailstock end. That way you don't have to keep lubricating the
center.

Did I not mention it? It is on my Lee Valley wish list...

:-)

Another issue is
facing off longish cylinders (the inner diameter of the spindle is
only 5/16") and I shall be needing a steady rest.

Yes -- you will.

But all of that had to be put on hold as I have not had a decent
arrangement to grind lathe bits. I finally finished it today.

It nearly burned down today. See my other post.

Ouch! I'll look for that. But it is rather late tonight, so I
might not see it until later today. (It is now approaching 1:30 AM. :-)

[...]

The primary purpose of *any* home shop is to make tools for the
tools. Any actual products other than this are a matter of luck -- or
testing the tools which you made. :-)

When I look at the list of things that are needed and compare it with the
work rate so far it is clear that this year will be written off unless I
start throwing money at the various issues. OTOH that would be nowhere near
as educational...

:-)

And the more you learn, the less damage you will do to purchased
tools. :-)

Enjoy,
DoN.

--
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--- Black Holes are where God is dividing by zero ---

DoN. Nichols wrote:
[...]

OK, I understand the procedure. Clearly this could have been done
neither as per the factory instruction nor using the kit provided.

Well ... it would have been possible to put the washer in there
behind the soft jaws and in contact with the master jaws.

I did not think I could get it in there - too big.

[...]

I did that and then turned and faced a 4.5" washer. The bottom
cleared the ways by about 1/8" and getting to the side of the disk
was a little tricky.

That is what the soft jaws are for. If the washer (or other
disc) is thinner than the steps of the jaws on the 4-jaw, you take a
new set of soft jaws for the 3-jaw, and turn them (after preloading)
to a step just deep enough to allow facing both sides. You can
actually make it a little deeper, and just expect to machine off a
bit of the height of the soft jaws as you do the first workpiece.
Remember -- the parts of the soft jaws are expendable. :-)

Yes. Just as well. I have already started expending them! With the 4-jaw I
just shimmed the workpiece.

Not to mention doing it at 575 rpm...

I would swear that mine will go slower than that. How many belt
steps are on your pulleys?

6. The biggest ratio is about 3, the motor runs at 1725. The figure is also
quoted by the Taig manufacturer.

And you could replace the motor with a three phase or a DC motor
and connect an appropriate controller to it to get speeds perhaps
1/6th your current speed. That would take you down to 100 RPM or a
bit slower. My 12" Clausing will go down to 210 RPM in direct drive,
and if I engage the back gear, it will go down to 35 RPM. The
corresponding highest speeds are 1600 RPM and 270 RPM. Having a
variable speed motor would be somewhat the equivalent of having a
back gear -- except that it would not boost the torque the way a back
gear does.

Or I could make a counter-shaft. Or spend $588 on a 7x8 and tweak the
controller - apparently one can get it from minimum 200 rpm down to 75. Or
(drum roll!!) I could use my RedNeck lathe which goes down to 80 (once I got
it on a stand and sorted out the tooling arrangement - no more than 3 years
from now...).

[...]
I started up on that. Inadvertently. The first parting tool I made
just did not cut it. It spun the toolpost and shaved the jaws before
I realized what was going on.

Clamp some heavy paper between the toolpost and the table or
compound and it will increase the holding power by fitting into

OK. Presumably there is a trade-off between the paper thickness and the need
to adjust the tool height. But with my little post that should not be an
issue.

But the advice on turning the OD jaws is noted. I also found some
good stuff he
http://www.ctemag.com/pdf/2002/0203-topchoices.pdf

related to what the shape of the jaws should be etc.

Of course, this is written from the perspective of someone who
is after 0.0001" runout -- and is working with a machine capable of
that. :-)

Isn't everybody?

[...]

OTOH the second (re-worked) parting tool works just fine. Once you
get past the squealing and screeching of the bigger OD down to about
3/8" :-)

Keeping the amount or projection down to a minimum helps a lot.
Making sure that the sides of the parting tool are parallel and
perpendicular to the axis of the workpiece helps. Having the parting
happening as close to the chuck's jaws as possible helps. Getting
lubricant to the bottom of the groove helps. And ideally, not having
a compound as part of the stackup will help minimize the flex of the
system.

Done all of the above. Still squeals like a banshee. But it is better than
it was with the original grind. Still have to keep backing out and clearing
out the chips before the tool digs in and stops the spindle - even when it
reaches the small diameter.

--
Michael Koblic
Campbell River, BC

On 2009-07-02, Michael Koblic wrote:
DoN. Nichols wrote:
[...]

OK, I understand the procedure. Clearly this could have been done
neither as per the factory instruction nor using the kit provided.

Well ... it would have been possible to put the washer in there
behind the soft jaws and in contact with the master jaws.

I did not think I could get it in there - too big.

The washer was larger in diameter than the minor diameter of the
threaded hole in the chuck back? Then mount it on a bolt and turn it
down a bit until it does fit. If it will fit the bore through the
chuck, that is small enough.

[ ... ]

Remember -- the parts of the soft jaws are expendable. :-)

Yes. Just as well. I have already started expending them! With the 4-jaw I
just shimmed the workpiece.

Shimming the workpiece has two disadvantages, depending on how
you do it all.

1) If they are kept behind the workpiece while turning, they are
likely to fling out at high speed.

2) If they are tapped out after the jaws are tightened, the
workpiece is likely to work its way in towards the chuck body as
you turn.

You *could* make the shims in the form of turned rings which go
around the last jaw step so there is nowhere for them to go even if the
workpiece is no longer firmly gripping them.

Not to mention doing it at 575 rpm...

I would swear that mine will go slower than that. How many belt
steps are on your pulleys?

6. The biggest ratio is about 3, the motor runs at 1725. The figure is also
quoted by the Taig manufacturer.

O.K. I went down and checked (it was early enough this evening
for me to find the mechanical tach and dig out the Taig to where I could
run it.)

Here are the speeds which I get - run by a 1/10 HP motor whose
"nameplate" (a sticky label) claims 1550 RPM.

The speeds which I measured a

1) 580 RPM

2) 905 RPM

3) 1430 RPM

4) 3260 RPM

5) 5150 RPM

Total of five belt steps with that little tiny belt. :-)

So -- it does run faster than I thought, and my impression that
it runs slower is probably because I seldom use it for anything large.
I've got other lathes more suited for that, and use these for really
small workpieces.

And you could replace the motor with a three phase or a DC motor
and connect an appropriate controller to it to get speeds perhaps
1/6th your current speed. That would take you down to 100 RPM or a
bit slower.

A DC motor, a Variac, and a rectifier would do a nice job there.
If you really care about spindle speed precision, a servo motor and
servo amplifier would be guilding the lilly. :-)

My 12" Clausing will go down to 210 RPM in direct drive,
and if I engage the back gear, it will go down to 35 RPM. The
corresponding highest speeds are 1600 RPM and 270 RPM. Having a
variable speed motor would be somewhat the equivalent of having a
back gear -- except that it would not boost the torque the way a back
gear does.

Or I could make a counter-shaft. Or spend $588 on a 7x8 and tweak the
controller - apparently one can get it from minimum 200 rpm down to 75. Or
(drum roll!!) I could use my RedNeck lathe which goes down to 80 (once I got
it on a stand and sorted out the tooling arrangement - no more than 3 years
from now...).

:-)

The countershaft might be a good idea. Two pulley steps (made
on the Taig) -- one for about 1:1 ratio, and the other for about 6:1
ratio. Or -- if you could pick up a slower motor, make the pulleys
identical, so they step up as much as they step down. A ratio of 2.45:1
(5:2 would be close enough) and a motor whose speed is about 600 RPM
would be nice (though 900 RPM is going to be easier to find, I think.
And bear in mind that the speeds I give above are with no slip. It will
be slower with normal slip. Fore example, the 1650 RPM motor would be
1800 RPM with no slip. (900 with no slip becomes something like 825
RPM with slip, and 600 with no slip becomes 550 RPM with slip.) That
550 RPM would get you down to 316 RPM with your existing gearing.

But a DC motor a Variac, and a rectifier would be more flexible,
giving you a much wider range of speeds, and the ability to change the
speed in mid cut without having to stop the motor and change the belts.

[...]
I started up on that. Inadvertently. The first parting tool I made
just did not cut it. It spun the toolpost and shaved the jaws before
I realized what was going on.

Clamp some heavy paper between the toolpost and the table or
compound and it will increase the holding power by fitting into

OK. Presumably there is a trade-off between the paper thickness and the need
to adjust the tool height. But with my little post that should not be an
issue.

Not much -- you can take out one shim about half the thickness
of the paper (it will compress that much when you tighten the bolt
holding the toolpost in place.)

But the advice on turning the OD jaws is noted. I also found some
good stuff he
http://www.ctemag.com/pdf/2002/0203-topchoices.pdf

related to what the shape of the jaws should be etc.

Of course, this is written from the perspective of someone who
is after 0.0001" runout -- and is working with a machine capable of
that. :-)

Isn't everybody?

:-)

[...]

OTOH the second (re-worked) parting tool works just fine. Once you
get past the squealing and screeching of the bigger OD down to about
3/8" :-)

Keeping the amount or projection down to a minimum helps a lot.
Making sure that the sides of the parting tool are parallel and
perpendicular to the axis of the workpiece helps. Having the parting
happening as close to the chuck's jaws as possible helps. Getting
lubricant to the bottom of the groove helps. And ideally, not having
a compound as part of the stackup will help minimize the flex of the
system.

Done all of the above. Still squeals like a banshee.

Interesting. I get rather quiet parting even with 3" diameter
stock -- but I'll probably be running at about 210 RPM.

But it is better than
it was with the original grind. Still have to keep backing out and clearing
out the chips before the tool digs in and stops the spindle - even when it
reaches the small diameter.

That is another reason to consider the rear-mounted parting
tool. Instead of digging in, it disengages a little when things flex.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Jul 2, 5:22*am, "DoN. Nichols" wrote:

* * * * A DC motor, a Variac, and a rectifier would do a nice job there.
If you really care about spindle speed precision, a servo motor and
servo amplifier would be guilding the lilly. :-)


* * * * But a DC motor a Variac, and a rectifier would be more flexible,
giving you a much wider range of speeds, and the ability to change the
speed in mid cut without having to stop the motor and change the belts.

[...]


* * * * Enjoy,
* * * * * * * * DoN.

Start looking at Craigslist or Freecycle for a treadmill. Most of
them have a DC motor and controler, but I did find one with a AC motor
and a varible speed pulley.

Look under Free and be patient.

Or look in Ebay for a small VFD and then locally for a small 3 phase
motor. I just got a 56 frame three phase motor for $5 at a garage
sale.

Dan

Dan

On 2009-07-02, wrote:
On Jul 2, 5:22*am, "DoN. Nichols" wrote:

* * * * A DC motor, a Variac, and a rectifier would do a nice job there.
If you really care about spindle speed precision, a servo motor and
servo amplifier would be guilding the lilly. :-)


* * * * But a DC motor a Variac, and a rectifier would be more flexible,
giving you a much wider range of speeds, and the ability to change the
speed in mid cut without having to stop the motor and change the belts.

[...]


* * * * Enjoy,
* * * * * * * * DoN.

Start looking at Craigslist or Freecycle for a treadmill. Most of
them have a DC motor and controler, but I did find one with a AC motor
and a varible speed pulley.

Are you complaining about them mostly being DC motors, or about
the one AC and the VS pulley assembly? Both would be interesting to me
Or did you get one assuming a DC motor, and when you got it home you
discovered the VS pulley?

Look under Free and be patient.

Or look in Ebay for a small VFD and then locally for a small 3 phase
motor. I just got a 56 frame three phase motor for $5 at a garage
sale.

That would be a good way to go -- though I think that the DC
motor would do better at really low speeds.

Of course -- I'm not the one looking for the slow speed motor,
just one responding. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On Jul 3, 3:02*am, "DoN. Nichols" wrote:


* * * * Are you complaining about them mostly being DC motors, or about
the one AC and the VS pulley assembly? *Both would be interesting to me
Or did you get one assuming a DC motor, and when you got it home you
discovered the VS pulley?

Not complaining. Just commenting. I acquired several treadmill
motors and found that one of them had a AC motor and a VS pulley. So
if you want a DC motor, check how the speed is controled. Like you I
found both interesting.

Cheap Variacs are a little hard to find. But a light dimmer or Router
speed control will work and I think will give you somewhat better
speed control than a Variac.

Dan


* * * * That would be a good way to go -- though I think that the DC
motor would do better at really low speeds.

* * * * Of course -- I'm not the one looking for the slow speed motor,
just one responding. :-)

* * * * Enjoy,
* * * * * * * * DoN.

--
*Email: * * | Voice (all times): (703) 938-4564
* * * * (too) near Washington D.C. |http://www.d-and-d.com/dnichols/DoN.html
* * * * * *--- Black Holes are where God is dividing by zero ---

DoN. Nichols wrote:

[...]

Shimming the workpiece has two disadvantages, depending on how
you do it all.

1) If they are kept behind the workpiece while turning, they are
likely to fling out at high speed.

2) If they are tapped out after the jaws are tightened, the
workpiece is likely to work its way in towards the chuck body as
you turn.


Ah. Did not think of No.1.

You *could* make the shims in the form of turned rings which go
around the last jaw step so there is nowhere for them to go even if
the workpiece is no longer firmly gripping them.

Noted for next time I have to do it with a 4-jaw.

[...]

And you could replace the motor with a three phase or a DC motor
and connect an appropriate controller to it to get speeds perhaps
1/6th your current speed. That would take you down to 100 RPM or a
bit slower.

A DC motor, a Variac, and a rectifier would do a nice job there.
If you really care about spindle speed precision, a servo motor and
servo amplifier would be guilding the lilly. :-)

I don't, but even the bare bones are not a cheap option as I found out
yesterday looking around eBay.

[...]

The countershaft might be a good idea. Two pulley steps (made
on the Taig) -- one for about 1:1 ratio, and the other for about 6:1
ratio. Or -- if you could pick up a slower motor, make the pulleys
identical, so they step up as much as they step down. A ratio of
2.45:1 (5:2 would be close enough) and a motor whose speed is about
600 RPM would be nice (though 900 RPM is going to be easier to find,
I think.

I was thinking of just getting two more Taig pulleys ($24.49) and making
*two* countershafts. The lowest speed would be just over 60 rpm. Even with
just one pulley the speed would be under 200. And the theoretical maximum
speed of 47,250 rpm. I wonder what the 3-jaw chuck sounds like at that
speed...

The two questions that bother me about the concept of a countershaft a

1) Is the 3M belt big enough withstand the torque at the lowest speeds? Or
would one have to go to a completely different transmission for the final
step (countershaft 2 to spindle), e.g. timing pulleys and belt?
2) If one were to make a pulley, how critical are the groove dimensions? The
only pulley I made was the wooden one (and it works just fine) but the
process can hardly be repeated with aluminium (or can it?)

And bear in mind that the speeds I give above are with no
slip. It will be slower with normal slip. Fore example, the 1650 RPM
motor would be 1800 RPM with no slip. (900 with no slip becomes
something like 825 RPM with slip, and 600 with no slip becomes 550
RPM with slip.) That 550 RPM would get you down to 316 RPM with
your existing gearing.

Ah, with slip I can get down to zero, no problem...

But a DC motor a Variac, and a rectifier would be more flexible,
giving you a much wider range of speeds, and the ability to change the
speed in mid cut without having to stop the motor and change the
belts.

That is clearly the preferred option but the prices I have seen so far
really make it uneconomical.

[...]

OTOH the second (re-worked) parting tool works just fine. Once you
get past the squealing and screeching of the bigger OD down to
about 3/8" :-)

Keeping the amount or projection down to a minimum helps a lot.
Making sure that the sides of the parting tool are parallel and
perpendicular to the axis of the workpiece helps. Having the
parting happening as close to the chuck's jaws as possible helps.
Getting lubricant to the bottom of the groove helps. And ideally,
not having a compound as part of the stackup will help minimize the
flex of the system.

Done all of the above. Still squeals like a banshee.

Interesting. I get rather quiet parting even with 3" diameter
stock -- but I'll probably be running at about 210 RPM.

Maybe I should reduce speed...:-)

That is another reason to consider the rear-mounted parting
tool. Instead of digging in, it disengages a little when things flex.

Would it then get rid of the chatter by allowing an increased feed rate? At
$5 that is the truly cheapest solution.

--
Michael Koblic
Campbell River, BC

wrote:

Start looking at Craigslist or Freecycle for a treadmill. Most of
them have a DC motor and controler, but I did find one with a AC motor
and a varible speed pulley.

Look under Free and be patient.

Or look in Ebay for a small VFD and then locally for a small 3 phase
motor. I just got a 56 frame three phase motor for $5 at a garage
sale.

I have been looking for a while at garage sales and local auction. I will
expand to Craigs list (where I follow other things). I saw one tread mill
motor at the auction here but it was about twice the size of the Taig
(2.5HP). I am told scroll saws are another possible source. Typically their
motors are rated for about 160 watts but that should do for the Taig (if Don
runs his off a 75W one).

--
Michael Koblic
Campbell River, BC

On Jul 2, 10:44*pm, "Michael Koblic" wrote:
...
The two questions that bother me about the concept of a countershaft a

1) Is the 3M belt big enough withstand the torque at the lowest speeds? Or
would one have to go to a completely different transmission for the final
step (countershaft 2 to spindle), e.g. timing pulleys and belt?
2) If one were to make a pulley, how critical are the groove dimensions? The
only pulley I made was the wooden one (and it works just fine) but the
process can hardly be repeated with aluminium (or can it?)

Michael Koblic
Campbell River, BC

I usually set the belt on my larger lathe to slip with nearly maximum
hand pressure, on the little one to slip fairly easily. The leather
belt changes length with humidity so I have to readjust it anyway. The
motor and countershaft are on a swinging frame with a tension
adjustment screw in series with a toggle linkage.

Here's an adjustable cam tensioner that's easy to make:
http://picasaweb.google.com/KB1DAL/H...33137678036386
The bolt through the disk is 0.05" off center to pull or release the
forged eyebolt in the slot. You could put it 1/4" off for a 1/2" throw
to tighten or move the belt. Rotate the handle for fine adjustment,
flip it to quickly tighten or loosen it.

Machinery's Handbook 23 gives the following groove geometry for a 4L
vee belt:
OD Angle Width
2.65 30 0.485
2.65 - 3.24 32 0.490
3.25 - 5.65 34 0.494
5.65 38 0.504

We discussed this here once, IIRC some posters used 35 degrees and
0.5" width for all diameters. You could try it and change the groove
angle if the belt appears to be wearing quickly, but I suspect you
can't drive a Taig hard enough to harm a belt. The heavily loaded pump
drive vee belt on my tractor ran for 3 years and still looked OK when
it failed with a broken cord. It ran on home-made pulleys.

jsw

On 2009-07-03, wrote:
On Jul 3, 3:02*am, "DoN. Nichols" wrote:


* * * * Are you complaining about them mostly being DC motors, or about
the one AC and the VS pulley assembly? *Both would be interesting to me
Or did you get one assuming a DC motor, and when you got it home you
discovered the VS pulley?

Not complaining. Just commenting. I acquired several treadmill
motors and found that one of them had a AC motor and a VS pulley. So
if you want a DC motor, check how the speed is controled. Like you I
found both interesting.

O.K.

Cheap Variacs are a little hard to find.

Granted. I collected mine long ago -- many from hamfests.

But a light dimmer or Router
speed control will work and I think will give you somewhat better
speed control than a Variac.

Not sure that the speed control is going to be better. In
particular, at the lowest speeds the behavior tends to be speed pulses
with those.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

On 2009-07-03, Michael Koblic wrote:
DoN. Nichols wrote:

[...]

Shimming the workpiece has two disadvantages, depending on how
you do it all.

1) If they are kept behind the workpiece while turning, they are
likely to fling out at high speed.

2) If they are tapped out after the jaws are tightened, the
workpiece is likely to work its way in towards the chuck body as
you turn.


Ah. Did not think of No.1.

You should *always* consider what might fly out when you could
be in the path.

You *could* make the shims in the form of turned rings which go
around the last jaw step so there is nowhere for them to go even if
the workpiece is no longer firmly gripping them.

Noted for next time I have to do it with a 4-jaw.

Note that I have never tried that design -- just thought of it
as a possibility -- and one which does not require different size rings
for each size of workpiece, since they are trapped by going around the
jaw ends.

[...]

And you could replace the motor with a three phase or a DC motor
and connect an appropriate controller to it to get speeds perhaps
1/6th your current speed. That would take you down to 100 RPM or a
bit slower.

A DC motor, a Variac, and a rectifier would do a nice job there.
If you really care about spindle speed precision, a servo motor and
servo amplifier would be guilding the lily. :-)

I don't, but even the bare bones are not a cheap option as I found out
yesterday looking around eBay.

Someone else suggested a light dimmer which is typically quite
inexpensive -- and as for motors -- a cheap hand held electric drill
could be clamped onto a shaft in bearings to drive at a lower speed.
Or -- you could salvage a motor out of a vacuum cleaner or a kitchen
blender or anything else with a DC/universal motor. (Just look for
brush holders to verify that it is not AC only -- and the holders may
be hidden inside, as is common in cheap hand held electric drills.)

[...]

The countershaft might be a good idea. Two pulley steps (made
on the Taig) -- one for about 1:1 ratio, and the other for about 6:1
ratio. Or -- if you could pick up a slower motor, make the pulleys
identical, so they step up as much as they step down. A ratio of
2.45:1 (5:2 would be close enough) and a motor whose speed is about
600 RPM would be nice (though 900 RPM is going to be easier to find,
I think.

I was thinking of just getting two more Taig pulleys ($24.49) and making
*two* countershafts.

Two extra pulleys (and an extra belt) would make *one*
countershaft, not two.

The lowest speed would be just over 60 rpm. Even with
just one pulley the speed would be under 200. And the theoretical maximum
speed of 47,250 rpm. I wonder what the 3-jaw chuck sounds like at that
speed...

Hmm ... what *is* the sound of a 3-jaw chuck flying into pieces.
That speed (if the motor could put out the needed torque) would
certainly explode the chuck. A 12" chuck is considered dangerous at a
bit over 3000 RPM IIRC.

The two questions that bother me about the concept of a countershaft a

1) Is the 3M belt big enough withstand the torque at the lowest speeds? Or
would one have to go to a completely different transmission for the final
step (countershaft 2 to spindle), e.g. timing pulleys and belt?

I would suggest that you make a timing pulleys and belt for the
step from the countershaft to the spindle to handle the extra torque.
Look for pulleys for about a 6:1 ratio which will get you down near 100
RPM or a bit more.

2) If one were to make a pulley, how critical are the groove dimensions?

The angle between the walls is critical, and the spacing has to
be tight enough so the belt does not touch the bottom.

The
only pulley I made was the wooden one (and it works just fine) but the
process can hardly be repeated with aluminium (or can it?)

It could be -- but a lot of careful filing. And it will take a
lot longer than doing it on the lathe. You will either need a compound
set to make the proper angle for the walls, or a form tool ground to cut
both angles at the same time. And I don't think that your machine can
handle the amount of metal removal involved in a form tool, even for
that small a belt groove.

And bear in mind that the speeds I give above are with no
slip. It will be slower with normal slip. Fore example, the 1650 RPM
motor would be 1800 RPM with no slip. (900 with no slip becomes
something like 825 RPM with slip, and 600 with no slip becomes 550
RPM with slip.) That 550 RPM would get you down to 316 RPM with
your existing gearing.

Ah, with slip I can get down to zero, no problem...

Yes -- you can get down to zero -- but between zero and a bit
below the nominal speed with slip you will have no torque to work with,
so the descent from normal slip to zero will be very sudden.

But a DC motor a Variac, and a rectifier would be more flexible,
giving you a much wider range of speeds, and the ability to change the
speed in mid cut without having to stop the motor and change the
belts.

That is clearly the preferred option but the prices I have seen so far
really make it uneconomical.

An electric drill motor (a hand-held electric drill is called a
"drill motor") with variable speed hooked to a shaft mounted in pulleys
should do it -- until the drill motor burns out. They typically don't
handle long run times well.

[...]

OTOH the second (re-worked) parting tool works just fine. Once you
get past the squealing and screeching of the bigger OD down to
about 3/8" :-)

Keeping the amount or projection down to a minimum helps a lot.
Making sure that the sides of the parting tool are parallel and
perpendicular to the axis of the workpiece helps. Having the
parting happening as close to the chuck's jaws as possible helps.
Getting lubricant to the bottom of the groove helps. And ideally,
not having a compound as part of the stackup will help minimize the
flex of the system.

Done all of the above. Still squeals like a banshee.

Interesting. I get rather quiet parting even with 3" diameter
stock -- but I'll probably be running at about 210 RPM.

Maybe I should reduce speed...:-)

And increase rigidity too -- which is another feature of my 12"
lathe which you don't have.

That is another reason to consider the rear-mounted parting
tool. Instead of digging in, it disengages a little when things flex.

Would it then get rid of the chatter by allowing an increased feed rate? At
$5 that is the truly cheapest solution.

You would still have chatter -- it just would not be as
destructive, and perhaps sound somewhat different.

Enjoy,
DoN.

--
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--- Black Holes are where God is dividing by zero ---

On 2009-07-03, Michael Koblic wrote:
wrote:

Start looking at Craigslist or Freecycle for a treadmill. Most of
them have a DC motor and controler, but I did find one with a AC motor
and a varible speed pulley.

Look under Free and be patient.

Or look in Ebay for a small VFD and then locally for a small 3 phase
motor. I just got a 56 frame three phase motor for $5 at a garage
sale.

I have been looking for a while at garage sales and local auction. I will
expand to Craigs list (where I follow other things). I saw one tread mill
motor at the auction here but it was about twice the size of the Taig
(2.5HP). I am told scroll saws are another possible source. Typically their
motors are rated for about 160 watts but that should do for the Taig (if Don
runs his off a 75W one).

Note that I don't do large diameter work on mine. I noticed
that the hand pressure holding the mechanical tach in the end of the
spindle would slow the spindle down a bit at the highest belt setting.

Also -- note that I have the WW (watchmaker's collet) spindle on
the lathe, which has a smaller pulley, and higher speeds than the normal
spindle does, so the speeds would be different on the standard spindle.

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
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--- Black Holes are where God is dividing by zero ---

Jim Wilkins wrote:
On Jul 2, 10:44 pm, "Michael Koblic" wrote:
...
The two questions that bother me about the concept of a countershaft
a

1) Is the 3M belt big enough withstand the torque at the lowest
speeds? Or would one have to go to a completely different
transmission for the final step (countershaft 2 to spindle), e.g.
timing pulleys and belt? 2) If one were to make a pulley, how
critical are the groove dimensions? The only pulley I made was the
wooden one (and it works just fine) but the process can hardly be
repeated with aluminium (or can it?)

Michael Koblic
Campbell River, BC

I usually set the belt on my larger lathe to slip with nearly maximum
hand pressure, on the little one to slip fairly easily. The leather
belt changes length with humidity so I have to readjust it anyway. The
motor and countershaft are on a swinging frame with a tension
adjustment screw in series with a toggle linkage.

Here's an adjustable cam tensioner that's easy to make:
http://picasaweb.google.com/KB1DAL/H...33137678036386
The bolt through the disk is 0.05" off center to pull or release the
forged eyebolt in the slot. You could put it 1/4" off for a 1/2" throw
to tighten or move the belt. Rotate the handle for fine adjustment,
flip it to quickly tighten or loosen it.

Mine is tensioned just by the motor weight which is clearly not enough. I
have seen people make some cool arrangements like rails on which the motor
slides. Incidentally my redNeck lathe will need something like that, too.

Machinery's Handbook 23 gives the following groove geometry for a 4L
vee belt:
OD Angle Width
2.65 30 0.485
2.65 - 3.24 32 0.490
3.25 - 5.65 34 0.494
5.65 38 0.504

We discussed this here once, IIRC some posters used 35 degrees and
0.5" width for all diameters. You could try it and change the groove
angle if the belt appears to be wearing quickly, but I suspect you
can't drive a Taig hard enough to harm a belt. The heavily loaded pump
drive vee belt on my tractor ran for 3 years and still looked OK when
it failed with a broken cord. It ran on home-made pulleys.

I am not sure I understand. How is the 4L belt dimension relevant to the
Taig? Are you saying I should change the whole drive train to 4L? Isn't it a
bit big for the machine?

--
Michael Koblic
Campbell River, BC

DoN. Nichols wrote:
Ah. Did not think of No.1.

You should *always* consider what might fly out when you could
be in the path.

As my old boss used to say: "You can recognize it only if you think of it."

Someone else suggested a light dimmer which is typically quite
inexpensive -- and as for motors -- a cheap hand held electric drill
could be clamped onto a shaft in bearings to drive at a lower speed.
Or -- you could salvage a motor out of a vacuum cleaner or a kitchen
blender or anything else with a DC/universal motor. (Just look for
brush holders to verify that it is not AC only -- and the holders may
be hidden inside, as is common in cheap hand held electric drills.)

1) I might be wrong but the DC motor controllers usually have a feed back
which will increase the power in response to loading conditions. I do not
see a light dimmer doing it.

2) A router speed regulator is a thought, however, typically these motors
turn at 30,000 rpm give or take so major gearing would still be required.
And I am still not sure about the feedback thing. Some routers have it built
in now (EVS).

3) I have a DC motor from an old Sears drill sitting somewhere. As it stands
it would also need the whole gear box to get the speed down to something
useable. The speed regulation with it is basically the slow start. When it
is turning slowly there is hardly any torque which brings me back to (1).

4) It is a thought to make a controller along the lines in (1) for the
motor. However, given that the motor is a 12V one I usspect that the current
at the lower speeds would be appreciable.

[...]

I was thinking of just getting two more Taig pulleys ($24.49) and
making *two* countershafts.

Two extra pulleys (and an extra belt) would make *one*
countershaft, not two.

How is that? One pulley=motor. Belt to second pulley=countershaft 1
(reduction by factor of 3) Belt to third pulley=counteshaft 2 (reduction by
factor of 9). Belt to spindle pulley (reduction by factor of 27). A single
coutershaft would require pulley 2 and 3 to be on the same shaft with no
reduction of speed between them.

The lowest speed would be just over 60 rpm.
Even with just one pulley the speed would be under 200. And the
theoretical maximum speed of 47,250 rpm. I wonder what the 3-jaw
chuck sounds like at that speed...

Hmm ... what *is* the sound of a 3-jaw chuck flying into pieces.
That speed (if the motor could put out the needed torque) would
certainly explode the chuck. A 12" chuck is considered dangerous at a
bit over 3000 RPM IIRC.

Or 2 rpm if dropped from a second storey window.
I know what sound a hockey puck travelling at 80 mph makes. I almost wish I
did not...

The two questions that bother me about the concept of a countershaft
a

1) Is the 3M belt big enough withstand the torque at the lowest
speeds? Or would one have to go to a completely different
transmission for the final step (countershaft 2 to spindle), e.g.
timing pulleys and belt?

I would suggest that you make a timing pulleys and belt for the
step from the countershaft to the spindle to handle the extra torque.
Look for pulleys for about a 6:1 ratio which will get you down near
100 RPM or a bit more.

Yes, that appears to be the consensus.

2) If one were to make a pulley, how critical are the groove
dimensions?

The angle between the walls is critical, and the spacing has to
be tight enough so the belt does not touch the bottom.


The only pulley I made was the wooden one (and it works just fine)
but the process can hardly be repeated with aluminium (or can it?)

It could be -- but a lot of careful filing. And it will take a
lot longer than doing it on the lathe. You will either need a
compound set to make the proper angle for the walls, or a form tool
ground to cut both angles at the same time. And I don't think that
your machine can handle the amount of metal removal involved in a
form tool, even for that small a belt groove.

Agree. I have demonstrated it with the first parting tool. In any case your
comments above re-timing pulley make this issue probably moot.

And bear in mind that the speeds I give above are with no
slip. It will be slower with normal slip. Fore example, the 1650
RPM motor would be 1800 RPM with no slip. (900 with no slip becomes
something like 825 RPM with slip, and 600 with no slip becomes 550
RPM with slip.) That 550 RPM would get you down to 316 RPM with
your existing gearing.

Ah, with slip I can get down to zero, no problem...

Yes -- you can get down to zero -- but between zero and a bit
below the nominal speed with slip you will have no torque to work
with, so the descent from normal slip to zero will be very sudden.

Also do not forget the smoke...

But a DC motor a Variac, and a rectifier would be more flexible,
giving you a much wider range of speeds, and the ability to change
the speed in mid cut without having to stop the motor and change the
belts.

That is clearly the preferred option but the prices I have seen so
far really make it uneconomical.

An electric drill motor (a hand-held electric drill is called a
"drill motor") with variable speed hooked to a shaft mounted in
pulleys should do it -- until the drill motor burns out. They
typically don't handle long run times well.

[...]

Interesting. I get rather quiet parting even with 3" diameter
stock -- but I'll probably be running at about 210 RPM.

Maybe I should reduce speed...:-)

And increase rigidity too -- which is another feature of my 12"
lathe which you don't have.

Story of my life...

--
Michael Koblic
Campbell River, BC

On 2009-07-04, Michael Koblic wrote:
DoN. Nichols wrote:
Ah. Did not think of No.1.

You should *always* consider what might fly out when you could
be in the path.

As my old boss used to say: "You can recognize it only if you think of it."

Well ... when anything is not firmly secured (and not just by
friction between two pieces which *could* shift) consider what would
happen should it slip. The better your imagination, the less likely you
will be hurt in reality.

Someone else suggested a light dimmer which is typically quite
inexpensive -- and as for motors -- a cheap hand held electric drill
could be clamped onto a shaft in bearings to drive at a lower speed.
Or -- you could salvage a motor out of a vacuum cleaner or a kitchen
blender or anything else with a DC/universal motor. (Just look for
brush holders to verify that it is not AC only -- and the holders may
be hidden inside, as is common in cheap hand held electric drills.)

1) I might be wrong but the DC motor controllers usually have a feed back
which will increase the power in response to loading conditions. I do not
see a light dimmer doing it.

The fancy controllers do -- by various techniques, not all of
which are immediately visible like an encoder or tach on the shaft.
Some controllers apply power to the motor winding in pulses whose width
are varied to change the power to the motor. During the moments between
those pulses, the motor is acting as a generator, and the motor can see
what the speed is by the voltage generated.

But consider things like an old Singer sewing machine motor and
controller (such are are on the model 221 portable). It is simply a
DC/universal motor and a foot pedal which controls the current to the
motor (AC, but DC would work just as well). The foot pedal is simply a
stack of blocks of resistance element between two electrodes. The
harder you step on the pedal, the harder the blocks are pressed
together, and the lower the resistance, so the faster the motor runs.

You don't *need* the kind of regulation which the fancy
controllers give for this lathe. And you could use a pedal speed
control from a Dremel (from before Dremels came with built-in speed
controllers). I can't find the Dremel ones on eBay at the moment, but
this looks as though it might work as well. It is poorly described, but
I expect a controller for a DC/universal motor.

Ebay auction # 260291509189

2) A router speed regulator is a thought, however, typically these motors
turn at 30,000 rpm give or take so major gearing would still be required.
And I am still not sure about the feedback thing. Some routers have it built
in now (EVS).

The speed regulator is based on the speed a given motor is
capable of. It won't make motors not designed for it turn at 30,000
RPM. Find a 120V motor which is closer to 1000-2000 RPM and see what
happens.

3) I have a DC motor from an old Sears drill sitting somewhere. As it stands
it would also need the whole gear box to get the speed down to something
useable. The speed regulation with it is basically the slow start. When it
is turning slowly there is hardly any torque which brings me back to (1).

This sounds good -- until you mention later that it is a 12V
motor, not a 120V motor.

4) It is a thought to make a controller along the lines in (1) for the
motor. However, given that the motor is a 12V one I usspect that the current
at the lower speeds would be appreciable.

You want a drill which plugs directly into the AC line, not one
which runs from batteries.

[...]

I was thinking of just getting two more Taig pulleys ($24.49) and
making *two* countershafts.

Two extra pulleys (and an extra belt) would make *one*
countershaft, not two.

How is that? One pulley=motor. Belt to second pulley=countershaft 1
(reduction by factor of 3) Belt to third pulley=counteshaft 2 (reduction by
factor of 9). Belt to spindle pulley (reduction by factor of 27). A single
coutershaft would require pulley 2 and 3 to be on the same shaft with no
reduction of speed between them.

Oh -- you are thinking of two belts on each pulley except the
end ones. That restricts you to combinations which don't need the same
groove for both incoming and outgoing power. And I think the lowest
speed with triple reduction would be both too slow for the size of the
machine and those tiny belts could not handle the transmission of power
over the last two stages.

Use timing belt pulleys. Figure the largest diameter which
would clear the base when mounted directly on the spindle, and then
look for the smallest pulley of the same pitch which will mount on the
countershaft. At a guess, you might be able to get a 5" diameter pulley
plus the belt on the spindle (make sure that it is available with a hub
which matches the OD of the spindle at that end), and assuming 5 teeth
per inch of circumference, that would be about 78 teeth. Then a smaller
pulley with 12 teeth would give about a 6:1 reduction in a single pass.

O.K. Looking in McMaster Carr's web site, I find 1/2" wide belt
pulleys with a 0.200" pitch (MXL series). Let's see the largest which will
fit within 5" diameter.

The range for this size is 60 teeth max and 10 teeth minimum, or
6:1 ratio.

OD Teeth Bore Cat No Price

0.87" 10 3/16" 57105K11 $7.40
1.13" 14 1/4" 57105K14 $7.51
3.80" 60 5/16" 57105K33 $17.15

So -- if you need to fit it on a 1/4" shaft, you will need at leat 14
teeth (60:14 ratio, or about 128 RPM for 550 RPM in.

If you can turn the end of the shaft down to 3/16", you get a full 6:1
ratio, or 91 RPM.

These (and others) are on McMaster Carr's catalog page 1044 via
the web. (You'll also need to select a belt to fit including the proper
spacing between pulleys.) The pulleys which I have listed are acetal
plastic, and I would suggest that you go for the steel ones listed a bit
later in the page for stronger gears. And you'll probably need to pin
the hubs instead of just use setscrews to get enough strength with the
small diameter shafts.

[ ... ]

And bear in mind that the speeds I give above are with no
slip. It will be slower with normal slip. Fore example, the 1650
RPM motor would be 1800 RPM with no slip. (900 with no slip becomes
something like 825 RPM with slip, and 600 with no slip becomes 550
RPM with slip.) That 550 RPM would get you down to 316 RPM with
your existing gearing.

Ah, with slip I can get down to zero, no problem...

Yes -- you can get down to zero -- but between zero and a bit
below the nominal speed with slip you will have no torque to work
with, so the descent from normal slip to zero will be very sudden.

Also do not forget the smoke...

A lot of smaller motors are "impedance protected", and can sit
there stalled forever without letting out the magic smoke. :-)

Enjoy,
DoN.

--
Email: | Voice (all times): (703) 938-4564
(too) near Washington D.C. | http://www.d-and-d.com/dnichols/DoN.html
--- Black Holes are where God is dividing by zero ---

On the DC side, I scored a high torque motor - 4 brushes at 90 degrees -
that is 24V. Came out of a small elderly scooter. Some of these are beginning
to come on line in lew of second/third/fourth generation 4 wheeler buggy/chair.

Martin

Michael Koblic wrote:
wrote:

Start looking at Craigslist or Freecycle for a treadmill. Most of
them have a DC motor and controler, but I did find one with a AC motor
and a varible speed pulley.

Look under Free and be patient.

Or look in Ebay for a small VFD and then locally for a small 3 phase
motor. I just got a 56 frame three phase motor for $5 at a garage
sale.

I have been looking for a while at garage sales and local auction. I will
expand to Craigs list (where I follow other things). I saw one tread mill
motor at the auction here but it was about twice the size of the Taig
(2.5HP). I am told scroll saws are another possible source. Typically their
motors are rated for about 160 watts but that should do for the Taig (if Don
runs his off a 75W one).

Martin H. Eastburn wrote:
On the DC side, I scored a high torque motor - 4 brushes at 90
degrees - that is 24V. Came out of a small elderly scooter. Some of
these are
beginning to come on line in lew of second/third/fourth generation 4
wheeler buggy/chair.

I saw something similar on eBay - 48 V.
My neighbour just bought a golf cart...no, that would be wrong!

--
Michael Koblic
Campbell River, BC

DoN. Nichols wrote:
[...]

But consider things like an old Singer sewing machine motor and
controller (such are are on the model 221 portable). It is simply a
DC/universal motor and a foot pedal which controls the current to the
motor (AC, but DC would work just as well). The foot pedal is simply
a stack of blocks of resistance element between two electrodes. The
harder you step on the pedal, the harder the blocks are pressed
together, and the lower the resistance, so the faster the motor runs.

I cannot imagine that a lot of torque was required of Singer sewing
machines. What hapens to torque at the lowest speeds?

You don't *need* the kind of regulation which the fancy
controllers give for this lathe. And you could use a pedal speed
control from a Dremel (from before Dremels came with built-in speed
controllers). I can't find the Dremel ones on eBay at the moment, but
this looks as though it might work as well. It is poorly described,
but
I expect a controller for a DC/universal motor.

Ebay auction # 260291509189

2) A router speed regulator is a thought, however, typically these
motors turn at 30,000 rpm give or take so major gearing would still
be required. And I am still not sure about the feedback thing. Some
routers have it built in now (EVS).

The speed regulator is based on the speed a given motor is
capable of. It won't make motors not designed for it turn at 30,000
RPM. Find a 120V motor which is closer to 1000-2000 RPM and see what
happens.

3) I have a DC motor from an old Sears drill sitting somewhere. As
it stands it would also need the whole gear box to get the speed
down to something useable. The speed regulation with it is basically
the slow start. When it is turning slowly there is hardly any torque
which brings me back to (1).

This sounds good -- until you mention later that it is a 12V
motor, not a 120V motor.

I got one of them drills, too. But again, what happens to the torque at the
low speed if using a rheostat? On mine there is a slow start feature which I
take to be nothing more than a rheostat. I can stop the chuck by hand at the
low speed.

4) It is a thought to make a controller along the lines in (1) for
the motor. However, given that the motor is a 12V one I usspect that
the current at the lower speeds would be appreciable.

You want a drill which plugs directly into the AC line, not one
which runs from batteries.

I got a 13.6V 20A power supply - that's 1/3HP.

[...]

Oh -- you are thinking of two belts on each pulley except the
end ones. That restricts you to combinations which don't need the
same groove for both incoming and outgoing power. And I think the
lowest
speed with triple reduction would be both too slow for the size of the
machine and those tiny belts could not handle the transmission of
power over the last two stages.

63 rpm. But I take the point about the torque.

Use timing belt pulleys. Figure the largest diameter which
would clear the base when mounted directly on the spindle, and then
look for the smallest pulley of the same pitch which will mount on the
countershaft. At a guess, you might be able to get a 5" diameter
pulley plus the belt on the spindle (make sure that it is available
with a hub which matches the OD of the spindle at that end), and
assuming 5 teeth
per inch of circumference, that would be about 78 teeth. Then a
smaller pulley with 12 teeth would give about a 6:1 reduction in a
single pass.

O.K. Looking in McMaster Carr's web site, I find 1/2" wide belt
pulleys with a 0.200" pitch (MXL series). Let's see the largest
which will fit within 5" diameter.

The range for this size is 60 teeth max and 10 teeth minimum, or
6:1 ratio.

OD Teeth Bore Cat No Price

0.87" 10 3/16" 57105K11 $7.40
1.13" 14 1/4" 57105K14 $7.51
3.80" 60 5/16" 57105K33 $17.15

So -- if you need to fit it on a 1/4" shaft, you will need at leat 14
teeth (60:14 ratio, or about 128 RPM for 550 RPM in.

If you can turn the end of the shaft down to 3/16", you get a full 6:1
ratio, or 91 RPM.

These (and others) are on McMaster Carr's catalog page 1044 via
the web. (You'll also need to select a belt to fit including the
proper spacing between pulleys.) The pulleys which I have listed are
acetal plastic, and I would suggest that you go for the steel ones
listed a bit later in the page for stronger gears. And you'll
probably need to pin
the hubs instead of just use setscrews to get enough strength with the
small diameter shafts.

This would mean turning the spindle shaft down to at least 3/8". I do not
think this is possible. AFAIK the spindle is 5/8" with a 5/16" ID. Some of
the plain bore pulleys have large enough bores but maximum of 24 teeth or
so.

It is beginning to feel like trying to make a silk purse out of a sow's ear.
Some limitations will have to be accepted I think.

12" swing,
Increased rigidity,
The Holy Grail...

--
Michael Koblic
Campbell River, BC

On Fri, 03 Jul 2009 23:34:17 -0500, "Martin H. Eastburn"
wrote:

On the DC side, I scored a high torque motor - 4 brushes at 90 degrees -
that is 24V. Came out of a small elderly scooter. Some of these are beginning
to come on line in lew of second/third/fourth generation 4 wheeler buggy/chair.

Martin

I might have some Omniturn 90vt DC servo motors. Encoders are likely
dead, but will run fine. Bout 3" in diameter, about 8" long with a 1/2"
shaft about 2" long.

Free but for the shipping if I can find em.

They are about 1/2 hp IRC.

Gunner


Michael Koblic wrote:
wrote:

Start looking at Craigslist or Freecycle for a treadmill. Most of
them have a DC motor and controler, but I did find one with a AC motor
and a varible speed pulley.

Look under Free and be patient.

Or look in Ebay for a small VFD and then locally for a small 3 phase
motor. I just got a 56 frame three phase motor for $5 at a garage
sale.

I have been looking for a while at garage sales and local auction. I will
expand to Craigs list (where I follow other things). I saw one tread mill
motor at the auction here but it was about twice the size of the Taig
(2.5HP). I am told scroll saws are another possible source. Typically their
motors are rated for about 160 watts but that should do for the Taig (if Don
runs his off a 75W one).


"Lenin called them "useful idiots," those people living in
liberal democracies who by giving moral and material support
to a totalitarian ideology in effect were braiding the rope that
would hang them. Why people who enjoyed freedom and prosperity worked
passionately to destroy both is a fascinating question, one still with us
today. Now the useful idiots can be found in the chorus of appeasement,
reflexive anti-Americanism, and sentimental idealism trying to inhibit
the necessary responses to another freedom-hating ideology, radical Islam"

Bruce C. Thornton, a professor of Classics at American University of Cal State Fresno

On Jul 3, 8:56*pm, "Michael Koblic" wrote:
Jim Wilkins wrote:
...

I am not sure I understand. How is the 4L belt dimension relevant to the
Taig? Are you saying I should change the whole drive train to 4L? Isn't it a
bit big for the machine?

--
Michael Koblic

Why would you want to change the rest of the transmission to the Taig
style? An oversized motor and belts will cost you a little extra
electricity but you can easily make them slip to not overstress the
lathe.

1/2" pulleys and 3/4/5L vee belts are the only drive components
readily available from hardware stores on weekends, at least around
here. And they work well with small electric and gas motors. If you
build drives from surplus rather than carefully engineering them, it's
very helpful to have very few variations of shaft size and belt type,
so you can recycle the growing collection of spares when you move on
to air compressors and bandsaws.

jsw

On Jul 4, 1:36*am, "DoN. Nichols" wrote:


* * * * Someone else suggested a light dimmer which is typically quite
inexpensive -- and as for motors -- a cheap hand held electric drill
could be clamped onto a shaft in bearings to drive at a lower speed. *
Or -- you could salvage a motor out of a vacuum cleaner or a kitchen
blender or anything else with a DC/universal motor. *(Just look for
brush holders to verify that it is not AC only -- and the holders may
be hidden inside, as is common in cheap hand held electric drills.)


* * * * Enjoy,
* * * * * * * * DoN.

That someone was me. Light dimmers work pretty well. They are a
stiffer source than a variac, and I believe the back emf from the
motor affects when the triac fires.
Another source for universal motors is WeedWackers. I bought one at a
garage sale recently for $5.

Dan