I decided to spend a little time yesterday working on the mini lathe. I've
got a nice after market 4 jaw chuck that is a lot better than the 3 jaw it
came with, but I still tend to only use the lathe for crude projects. I get
more accuracy on the mini mill if I tighten the pinch nuts and adjust the
gibs before a project. Yesterday morning I used it to shorten and dome the
heads of a couple bolts for the catch on a clay pigeon launcher. I was yet
again impressed with how I really don't care for this machine all that much.
Still it did the job. Afterwards I decided to retrue all my mating
surfaces. I had never trued the front of the adaptor plate for the new
chuck/ I just assumed it was good since I had gotten it from a good source.
Turns out I was probably right, but I didn't check it first.

First was a retouch of the plate on the head stock. Not bad. Took off
uniform material all the way across. Then to separate the chuck from the
adaptor. It seemed good, but there were a couple spots that seemed low.
Odd. Just like a little puddle area. Its uniform now. Then I ran a
straight edge across the heads of the bolts in the adaptor plate. Oops.
They just hit now. A little milling on the heads of the bolts and it all
went together nicely. I don't have a piece of precision tool rod handy so I
chucked up an end mill in the lathe. At high speed it looked a little
blurry, so I ran it at low speed with a dial indicator on the smooth part of
the shaft, and I got a consistent smooth turn except for a bump of about
..006 - .007 on one side. Just to make sure it wasn't the end mill I marked
it with a sharpie and rotated it 180 degrees. There was still a bump on the
same side of the chuck when indicating the end mill. I suspect one jaw is
just a tad short of the other three. I was thinking about taking Varmint
Al's approach to truing them up as he detailed he

Page
http://varmintal.com/alath.htm

Pic
http://varmintal.com/grind1.jpg

It should be easy enough mount a rotary handpiece better than the tool he
used to do the job. There are three Foredom handpieces and three generics
in the parts bins under the Taig. Just make up a simple mounting bracket
like I used on the mini mill.

Is there a better way?

I figured I'ld put it in high gear, crank it up and watch for sparks with
the magnifying glass.

"Bob La Londe" wrote in message
...
I decided to spend a little time yesterday working on the mini lathe. I've
got a nice after market 4 jaw chuck that is a lot better than the 3 jaw it
came with, but I still tend to only use the lathe for crude projects. I
get more accuracy on the mini mill if I tighten the pinch nuts and adjust
the gibs before a project. Yesterday morning I used it to shorten and dome
the heads of a couple bolts for the catch on a clay pigeon launcher. I was
yet again impressed with how I really don't care for this machine all that
much. Still it did the job. Afterwards I decided to retrue all my mating
surfaces. I had never trued the front of the adaptor plate for the new
chuck/ I just assumed it was good since I had gotten it from a good
source. Turns out I was probably right, but I didn't check it first.

First was a retouch of the plate on the head stock. Not bad. Took off
uniform material all the way across. Then to separate the chuck from the
adaptor. It seemed good, but there were a couple spots that seemed low.
Odd. Just like a little puddle area. Its uniform now. Then I ran a
straight edge across the heads of the bolts in the adaptor plate. Oops.
They just hit now. A little milling on the heads of the bolts and it all
went together nicely. I don't have a piece of precision tool rod handy so
I chucked up an end mill in the lathe. At high speed it looked a little
blurry, so I ran it at low speed with a dial indicator on the smooth part
of the shaft, and I got a consistent smooth turn except for a bump of
about .006 - .007 on one side. Just to make sure it wasn't the end mill I
marked it with a sharpie and rotated it 180 degrees. There was still a
bump on the same side of the chuck when indicating the end mill. I
suspect one jaw is just a tad short of the other three. I was thinking
about taking Varmint Al's approach to truing them up as he detailed he

Page
http://varmintal.com/alath.htm

Pic
http://varmintal.com/grind1.jpg

It should be easy enough mount a rotary handpiece better than the tool he
used to do the job. There are three Foredom handpieces and three generics
in the parts bins under the Taig. Just make up a simple mounting bracket
like I used on the mini mill.

Is there a better way?

I figured I'ld put it in high gear, crank it up and watch for sparks with
the magnifying glass.


My experience with these Chinese machines is that anything that is not
visible has not been deburred. I would check the jaws and scroll for burrs
before doing anything drastic. Also check that you see the same runout when
chucking to a different diameter; it might be the scroll that is off.

If you have not done it yet, check the mating of the carriage V and flat to
the bed. I found that filing and scraping this to fit better made a big
difference. The lathe felt much more solid.

Bob La Londe wrote:
I decided to spend a little time yesterday working on the mini lathe.
I've got a nice after market 4 jaw chuck that is a lot better than the
3 jaw it came with, but I still tend to only use the lathe for crude
projects. I get more accuracy on the mini mill if I tighten the pinch
nuts and adjust the gibs before a project. Yesterday morning I used
it to shorten and dome the heads of a couple bolts for the catch on a
clay pigeon launcher. I was yet again impressed with how I really
don't care for this machine all that much. Still it did the job.
Afterwards I decided to retrue all my mating surfaces. I had never
trued the front of the adaptor plate for the new chuck/ I just
assumed it was good since I had gotten it from a good source. Turns
out I was probably right, but I didn't check it first.

First was a retouch of the plate on the head stock. Not bad. Took
off uniform material all the way across. Then to separate the chuck
from the adaptor. It seemed good, but there were a couple spots that
seemed low. Odd. Just like a little puddle area. Its uniform now.
Then I ran a straight edge across the heads of the bolts in the
adaptor plate. Oops. They just hit now. A little milling on the
heads of the bolts and it all went together nicely. I don't have a
piece of precision tool rod handy so I chucked up an end mill in the
lathe. At high speed it looked a little blurry, so I ran it at low
speed with a dial indicator on the smooth part of the shaft, and I got
a consistent smooth turn except for a bump of about .006 - .007 on one
side. Just to make sure it wasn't the end mill I marked it with a
sharpie and rotated it 180 degrees. There was still a bump on the
same side of the chuck when indicating the end mill. I suspect one
jaw is just a tad short of the other three. I was thinking about
taking Varmint Al's approach to truing them up as he detailed he

Page
http://varmintal.com/alath.htm

Pic
http://varmintal.com/grind1.jpg

It should be easy enough mount a rotary handpiece better than the tool
he used to do the job. There are three Foredom handpieces and three
generics in the parts bins under the Taig. Just make up a simple
mounting bracket like I used on the mini mill.

Is there a better way?

I figured I'ld put it in high gear, crank it up and watch for sparks
with the magnifying glass.



Does your 3 jaw that the lathe came with have a master tightening
socket?, usually marked with a 0 in my experience. If so this is the
socket that when the chuck is tightened with that socket will give the
minimum runout, at least for quality chucks when new.

On 2010-11-08, Bob La Londe wrote:
I decided to spend a little time yesterday working on the mini lathe. I've
got a nice after market 4 jaw chuck that is a lot better than the 3 jaw it
came with, but I still tend to only use the lathe for crude projects.

[ ... ]

First was a retouch of the plate on the head stock. Not bad. Took off
uniform material all the way across. Then to separate the chuck from the
adaptor. It seemed good, but there were a couple spots that seemed low.
Odd. Just like a little puddle area. Its uniform now. Then I ran a
straight edge across the heads of the bolts in the adaptor plate. Oops.
They just hit now. A little milling on the heads of the bolts and it all
went together nicely. I don't have a piece of precision tool rod handy so I
chucked up an end mill in the lathe. At high speed it looked a little
blurry, so I ran it at low speed with a dial indicator on the smooth part of
the shaft, and I got a consistent smooth turn except for a bump of about
.006 - .007 on one side. Just to make sure it wasn't the end mill I marked
it with a sharpie and rotated it 180 degrees. There was still a bump on the
same side of the chuck when indicating the end mill. I suspect one jaw is
just a tad short of the other three.

Huh? I thought that this was an *independent* 4-jaw chuck -- a
separate adjustment for each jaw. You tune out the runout by loosening
the side opposite the high point, tightening the side which has the high
point, and re-tightening the opposite side. If it is between two jaws,
you will need to do this with both pairs of jaws. Tune it that way
before jumping to the conclusion that it needs truing.

Using the grinder (as a toolpost grinder) on an independent
4-jaw chuck -- all you will be able to do is to make sure that the
gripping surfaces are parallel to the bed axis.

If it is a universal 4-jaw chuck instead (one where a single key
adjusts all four at once -- and those are rare) -- that is better used
on square workpieces, not on round. But you might indeed be able to
true it up a bit with the grinder.

I was thinking about taking Varmint
Al's approach to truing them up as he detailed he

Page
http://varmintal.com/alath.htm

I notice no warning about protecting the bed and all other
precision surfaces from the grit produced by the grinder. Cover all
surfaces -- either with newspaper wet with WD-40, or with aluminum foil,
and be careful to not spill the collected grit on the precision
surfaces. Protect *everything* below the toolpost. This includes the
spindle bearings, too -- and leadscrews -- and tailstock ram.

Good Luck,
DoN.

--
Remove oil spill source from e-mail
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--- Black Holes are where God is dividing by zero ---

On 11/8/2010 10:02 PM, DoN. Nichols wrote:
On 2010-11-08, Bob La wrote:
I decided to spend a little time yesterday working on the mini lathe. I've
got a nice after market 4 jaw chuck that is a lot better than the 3 jaw it
came with, but I still tend to only use the lathe for crude projects.

[ ... ]

First was a retouch of the plate on the head stock. Not bad. Took off
uniform material all the way across. Then to separate the chuck from the
adaptor. It seemed good, but there were a couple spots that seemed low.
Odd. Just like a little puddle area. Its uniform now. Then I ran a
straight edge across the heads of the bolts in the adaptor plate. Oops.
They just hit now. A little milling on the heads of the bolts and it all
went together nicely. I don't have a piece of precision tool rod handy so I
chucked up an end mill in the lathe. At high speed it looked a little
blurry, so I ran it at low speed with a dial indicator on the smooth part of
the shaft, and I got a consistent smooth turn except for a bump of about
.006 - .007 on one side. Just to make sure it wasn't the end mill I marked
it with a sharpie and rotated it 180 degrees. There was still a bump on the
same side of the chuck when indicating the end mill. I suspect one jaw is
just a tad short of the other three.

Huh? I thought that this was an *independent* 4-jaw chuck -- a
separate adjustment for each jaw. You tune out the runout by loosening
the side opposite the high point, tightening the side which has the high
point, and re-tightening the opposite side. If it is between two jaws,
you will need to do this with both pairs of jaws. Tune it that way
before jumping to the conclusion that it needs truing.

Using the grinder (as a toolpost grinder) on an independent
4-jaw chuck -- all you will be able to do is to make sure that the
gripping surfaces are parallel to the bed axis.

Grinding the jaws of a scroll chuck will ensure that they run true at
that diameter only. Any other diameter workpiece - larger or smaller,
may or may not be true.

"DoN. Nichols" wrote in message
...
On 2010-11-08, Bob La Londe wrote:
I decided to spend a little time yesterday working on the mini lathe.
I've
got a nice after market 4 jaw chuck that is a lot better than the 3 jaw
it
came with, but I still tend to only use the lathe for crude projects.

[ ... ]

First was a retouch of the plate on the head stock. Not bad. Took off
uniform material all the way across. Then to separate the chuck from the
adaptor. It seemed good, but there were a couple spots that seemed low.
Odd. Just like a little puddle area. Its uniform now. Then I ran a
straight edge across the heads of the bolts in the adaptor plate. Oops.
They just hit now. A little milling on the heads of the bolts and it all
went together nicely. I don't have a piece of precision tool rod handy
so I
chucked up an end mill in the lathe. At high speed it looked a little
blurry, so I ran it at low speed with a dial indicator on the smooth part
of
the shaft, and I got a consistent smooth turn except for a bump of about
.006 - .007 on one side. Just to make sure it wasn't the end mill I
marked
it with a sharpie and rotated it 180 degrees. There was still a bump on
the
same side of the chuck when indicating the end mill. I suspect one jaw
is
just a tad short of the other three.

Huh? I thought that this was an *independent* 4-jaw chuck -- a
separate adjustment for each jaw. You tune out the runout by loosening
the side opposite the high point, tightening the side which has the high
point, and re-tightening the opposite side. If it is between two jaws,
you will need to do this with both pairs of jaws. Tune it that way
before jumping to the conclusion that it needs truing.

Using the grinder (as a toolpost grinder) on an independent
4-jaw chuck -- all you will be able to do is to make sure that the
gripping surfaces are parallel to the bed axis.

If it is a universal 4-jaw chuck instead (one where a single key
adjusts all four at once -- and those are rare)

I don't think they are all that rare. There are lots of them for sale, and
this is what I have.

-- that is better used
on square workpieces, not on round. But you might indeed be able to
true it up a bit with the grinder.

It does seem to grip aluminum pieces better with less force and less
scaring.

I was thinking about taking Varmint
Al's approach to truing them up as he detailed he

Page
http://varmintal.com/alath.htm

I notice no warning about protecting the bed and all other
precision surfaces from the grit produced by the grinder. Cover all
surfaces -- either with newspaper wet with WD-40, or with aluminum foil,
and be careful to not spill the collected grit on the precision
surfaces. Protect *everything* below the toolpost. This includes the
spindle bearings, too -- and leadscrews -- and tailstock ram.

Good advice.

After my original post I found another surface that was way out of true.
One I had not expected it to be an engaging surface. Oops. Measure
everything I guess. On the adaptor plate there is a flat where the bolt
holes are and then a cylindrical protrusion in the middle. I expected it
was there only for alignment. It turned out to be taller than the
depression in the back of the chuck. I do not know if that should be the
surface to engage the chuck or if I should face it off so that the outer
flat engages the chuck.

On Nov 9, 11:00*am, "Bob La Londe" wrote:
...I suspect one jaw is just a tad short of the other three....

Show us some photos. There may be other options.

jsw

"Jim Wilkins" wrote in message
...
On Nov 9, 11:00 am, "Bob La Londe" wrote:
...I suspect one jaw is just a tad short of the other three....

Show us some photos. There may be other options.

jsw

Ok, I am just about out of ideas. One thing to note though is everything I
have done has improved it some. I have concluded (several steps ago) that
the majority of the problem is a wobble somewhere. I cut the cylinder on
the adaptor plate down so it just sets in the chuck but does not contact on
the face and I get .0023 apx at the tip of the jaws with and .0036 an inch
away from the jaws. Sounds like wobble, not an out of center condition like
a jaw being off would cause or mounting off center. Some mating surface or
the chuck itself still isn't true. The only surface I have left that I
could try to true up is the back of the chuck, and I haven't a clue how I
would do that except in another lathe. One that is already good.

I gave up on the jaws a while ago by testing with some shim stock and
opening and tightening over and over again to get a feel for where it starts
to grip. They are not perfect, but they are not the main problem.

I do wish I didn't have to remove the adaptor plate from the spindle plate
in order to remove the chuck. It always makes me nervous that I am getting
a piece of dross somewhere during reassembly. I have marked the plate(s),
chuck, bolts, and nuts so it gets reassembled the same every time.

Well, off to my day job. I'll play with this again this evening.

On 2010-11-09, Bob La Londe wrote:
"DoN. Nichols" wrote in message
...

[ ... ]

Huh? I thought that this was an *independent* 4-jaw chuck -- a
separate adjustment for each jaw. You tune out the runout by loosening
the side opposite the high point, tightening the side which has the high
point, and re-tightening the opposite side. If it is between two jaws,
you will need to do this with both pairs of jaws. Tune it that way
before jumping to the conclusion that it needs truing.

Using the grinder (as a toolpost grinder) on an independent
4-jaw chuck -- all you will be able to do is to make sure that the
gripping surfaces are parallel to the bed axis.

If it is a universal 4-jaw chuck instead (one where a single key
adjusts all four at once -- and those are rare)

I don't think they are all that rare. There are lots of them for sale, and
this is what I have.

Where did you find this -- and why did you get it? The usual
advice of getting a 4-jaw chuck for minimizing runout is assuming that
the 4-jaw is an independent 4-jaw, not a universal (scroll back) chuck.

An independent 4-jaw is a bit more work to tweak true when
mounting a workpiece -- but you can get it as true as your patience
holds for.

Yes -- I have a universal 4-jaw for my Compact-5/CNC lathe, but
it was a mistake in the ordering, as I wanted an independent one. So,
what I wound up doing was modifying a 4-jaw chuck for a Taig lathe
(similar size) to properly mount on the Compact-5's spindle, and then
ordered a replacement 4-jaw for the Taig from a (then) regular of this
newsgroup.

-- that is better used
on square workpieces, not on round. But you might indeed be able to
true it up a bit with the grinder.

It does seem to grip aluminum pieces better with less force and less
scaring.

If you want *that* -- go for a 6-jaw (or for things small enough
and a lathe large enough, use a collet). The 6-jaw is particularly nice
when working on relatively thin-walled tubing. Six points instead of
three means less deflection of the walls for a given grip strength.

I was thinking about taking Varmint
Al's approach to truing them up as he detailed he

Page
http://varmintal.com/alath.htm

I notice no warning about protecting the bed and all other
precision surfaces from the grit produced by the grinder. Cover all
surfaces -- either with newspaper wet with WD-40, or with aluminum foil,
and be careful to not spill the collected grit on the precision
surfaces. Protect *everything* below the toolpost. This includes the
spindle bearings, too -- and leadscrews -- and tailstock ram.

Good advice.

After my original post I found another surface that was way out of true.
One I had not expected it to be an engaging surface. Oops. Measure
everything I guess. On the adaptor plate there is a flat where the bolt
holes are and then a cylindrical protrusion in the middle. I expected it
was there only for alignment. It turned out to be taller than the
depression in the back of the chuck. I do not know if that should be the
surface to engage the chuck or if I should face it off so that the outer
flat engages the chuck.

O.K. The register projection in the backplate should not bottom
in the chuck. You probably turned off enough while truing the mount
flange so the effective projection was increased beyond what was needed.
Turn off enough of that projection so it does not bottom.. It *is* just
for alignment.

Enjoy,
DoN.

--
Remove oil spill source from e-mail
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 2010-11-09, Bob La Londe wrote:


"Jim Wilkins" wrote in message
...
On Nov 9, 11:00 am, "Bob La Londe" wrote:
...I suspect one jaw is just a tad short of the other three....

Show us some photos. There may be other options.

jsw

Ok, I am just about out of ideas. One thing to note though is everything I
have done has improved it some. I have concluded (several steps ago) that
the majority of the problem is a wobble somewhere. I cut the cylinder on
the adaptor plate down so it just sets in the chuck but does not contact on
the face and I get .0023 apx at the tip of the jaws with and .0036 an inch
away from the jaws. Sounds like wobble, not an out of center condition like
a jaw being off would cause or mounting off center. Some mating surface or
the chuck itself still isn't true. The only surface I have left that I
could try to true up is the back of the chuck, and I haven't a clue how I
would do that except in another lathe. One that is already good.

There is a way to do it, but you would wind up having to true
the register cavity at the back of the chuck, which would mean that it
is larger, and will need to machine a new backplate to match that.

The trick is to take a piece of steel which is the biggest which
you can hold in your (other) chuck, clamp it, turn the diameter down a
little where it extends from the chuck jaws to produce a surface which
*is* true -- no matter how bad the chuck may be (don't release it from
the chuck until you are done, or you will have to re-true). Once you
have this surface, clamp the chuck you are working on, backwards, and
you now can true the outer rim which contacts the backplate to match the
jaws.

*But* -- *don't* do that. You have *now* gotten to the point
where grinding the jaws to true them makes sense. The gripping surfaces
are not square to the axis around which the chuck rotates. It doesn't
matter whether the actual error comes from some other part. Once you
have the jaws trued, it will neutralize everything else. I was
objecting tot the truing of the jaws before when I was thinking that it
was an independent 4-jaw chuck, not a universal.

BTW That 0.0023" runout at the exit of the jaws is probably close
to the best you can expect to get from a universal chuck. After
grinding the jaws, you will probably be better than that when
gripping something the same diameter as the setting of the jaws
when you ground -- but at other diameters you can have more
error.


And that 2000 RPM to move the jaws out may or may not be enough,
depending on how stiff the jaw motion in their ways happens to be. For
a 3-jaw, you can put three identical width pieces of steel between the
angled faces of the jaws to preload them all out. That *might* work
with the 4-jaw universal which you have as well.

And running the chuck at high speeds with nothing gripped can
result in the jaws working out and flying across the room, again
depending on how stiff the motion actually is.

I gave up on the jaws a while ago by testing with some shim stock and
opening and tightening over and over again to get a feel for where it starts
to grip. They are not perfect, but they are not the main problem.

I do wish I didn't have to remove the adaptor plate from the spindle plate
in order to remove the chuck. It always makes me nervous that I am getting
a piece of dross somewhere during reassembly. I have marked the plate(s),
chuck, bolts, and nuts so it gets reassembled the same every time.

This is one of the reasons which make this kind of lathe more
awkward to use than the various other ways of mounting the chuck to the
spindle. The ones which I have (varying degrees of) experience with
a

1) The threaded spindle. The backplate (with chuck a part of it)
simply screws onto the spindle nose. This is fine until you
want to machine with the spindle in reverse for whatever reason
at which point the chuck can wind up unscrewing.

2) The Long-Taper (L-00 is my example). A long taper with a key
to prevent the chuck from rotating around the spindle, and a
threaded collar which screws onto a male thread at the back of
the chuck's backplate and draws it firmly onto the taper.

3) The Hardinge spindle nose. A long taper with a milled slot
in it which looks like a very wide topped 'Y' (or a slightly
angled 'T'. The chuck slide in place with the pin engaging the
slot and is then rotated to let the angle of the top bar pull it
on firmly.

4) The 'D' series -- a very short central taper and a number of
pins which vary with the size protruding from the backplate,
which go into holes in the spindle nose and are drawn in with
cams in the spindle rotated by a key like a chuck key. (There
is a cut in the side of each of the pins which engages the cams.)

5) The chuck slides on over the spindle nose (e.g. the chucks on
my Compact-5/CNC) with a register (40mm in this case) to assure
concentricity, and three or four Allen head cap screws go
through the chuck into threaded holes in the face of the
spindle. You can't remove or install the chuck while it is
holding a large workpiece, because that blocks access to the
screw heads -- but no need to disassemble the chuck from an
adaptor to remove it.

6) Chuck on a collet body, so it can be used in a lathe set up
for collets. This is the standard way for watchmaker's lathes.
I've got a pair of these in 5C collet size (a 3-jaw and a 4-jaw
independent) which are convenient when I don't need to put the
larger chucks (6" 3-jaw and 10" 4-jaw) on the spindle, because
those are *heavy*.

There are certainly other system which I don't have any
experience with -- but the thing in common for *all* of these is that they
don't require disassembling the chuck from an adaptor.

The nuts probably don't matter but the marking is in general a
good idea.

Well, off to my day job. I'll play with this again this evening.

Good Luck,
DoN.

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"DoN. Nichols" wrote in message
...

O.K. The register projection in the backplate should not bottom
in the chuck. You probably turned off enough while truing the mount
flange so the effective projection was increased beyond what was needed.
Turn off enough of that projection so it does not bottom.. It *is* just
for alignment.

Thanks for all the help Don. Had some big service jobs come in the last
couple days and have not had time to play with this, but now I am torn
between taking it all apart and taking one more finish pass at the adaptor
plate or just taking a swing at that jaws with a rotary tool. Maybe I'll
decide by tomorrow when I have time to play again.