On Fri, 12 Nov 2010 18:20:28 -0500, "Wild_Bill"
wrote:

By taking the MT arbor out of the spindle and rotating it 180 degrees
(required for arbors with tangs, obviously), one could take comparison
measurements. Differences may reveal where the inaccuracies are.

I would be switching arbors and substituting a different chuck, too. After
switching tooling, and another set of measurements, it should become clear
where all of the runout is coming from.

One of those MT arbor blanks with just a 1" (or other size) head/stub on
them, could be very helpful in checking out the MT socket relative to the
spindle's center axis.
I'd make a durable mark on the spindle and start checking runout on the
stub, which would be located cloe to the end of the spindle at this time.
The arbor stub OD might not be perfectly concentric with the centerline of
the MT taper, but it should be very close if the arbor was finish ground
between centers.

I was thinking along those lines today and tried to remove the chuck
from its JT33 arbor to do the checking. It seems to be glued on.

If the stub doesn't have a center hole, then it probably wasn't finish
ground between centers, so a little touchup may be required. I'd then make a
durable mark on the arbor in line with the previous mark on the spindle, and
touch the stub with a die grinder stone (held by a rigid fixture mounted to
the machine table) to make a small zone/pathway that's concentric to the
spindle's centerline.

Measurment of the newly ground path should show nearly perfect
concentricity.
If the error is excessive, I'd probably suspect a very poor grade of
bearings.

This is where I get confused: What is an "excessive" error? Looking at
the Jacobs web-page their keyed chucks are guaranteed at best 0.003"
TIR, some considerably worse. I seem to be within this figure.

I suppose this procedure could also be used on a drill chuck arbor, since
the grinding zone only needs to be small, and could be outside of the taper
where the chuck body seats.

The previous steps would verify if the bore of the MT spindle socket is
good, but won't help with the head/spindle-to-base perpendicularity issue.

True. I suspect at some stage I shall have to accept that one cannot
make a silk purse out of a sow's ear :-)

However, going through this process has been helpful. At least I
understand better where the sources of error are and even managed to
reduce some of them with relatively simple adjustments.

Michael Koblic,
Campbell River, BC

dan wrote:
John wrote in
rec.crafts.metalworking on Wed, 10 Nov 2010 21:25:39 -0500:

A 120 degree spotting drill makes it easy to calculate the spotting
drill depth if you want to pre chanfer the hole. The chamfer diameter
will be twice the drilling depth of the spotting drill. If you are
drilling and tapping a 5/16 rhreaded hole you would drill half the 5/16
depth plus the added depth for the chamfer.

John

Are you sure that's not 90 degree spotting drills that work that way?


Dan
You are absolutely right.

John

On 2010-11-13, wrote:
On 12 Nov 2010 06:01:52 GMT, "DoN. Nichols"
wrote:

My WML hates you. It swallowed your post again. OTOH it is not
prejudiced, it swallowed my last reply, too.

:-)

It knows that I do not trust Windows and reciprocates. :-)

[ ... ]

3) In a collet the figures were 0.001", 0.0015" and 0.002"

Better, but not perfect. How are your collets mounted? Since
you don't use R8, presumably you have a Morse taper shank socket and a
Morse taper holder for something like ER collets. (Or perhaps you are
using Morse taper collets?) I can't remember the details of your
machine at a distance like this. :-)

I did some repeats after the tramming today. The collets are Chinese
ER look-alikes on a MT3 shank.

O.K. So chips on the surface of the MT3 shank or in the socket
can introduce errors.

However -- you might test the runout inside the cone of the
adaptor which supports the collets.

Of course -- chips in the ER taper can introduce errors too, as
can chips in the collets themselves.

Today the dowel pin run perfectly parallel at 0.0015" in a collet.

Great!

I put the No. 3 and 4 center drills in their respective collets and
they run at 0.001" both.

Also great!

I put the chuck back in. The dowel pin run 0.002 at "zero" and 4"! But
then I repositioned it slightly and re tightened and the wobble
appeared - 0.004" at 4".

Since you are using ER style collets -- you should be able to
cover the whole range that the chuck can hold (assuming a full set of
collets), so why not *use* the collets?

I tried the center drills: No.3 was better initially at 0.003", but re
tightening I could make it 0.005".

No. 4 was 0.007"

For the sake of comparison I put the dowel pin in my drill press:
0.0035" and 0.007" at "zero" and 4".

How much could you move the stationary spindle by pushing
sideways on the chuck in various directions? Usually, the fit of the
quill to the headstock in a drillpress -- especially an import one --
can be pretty bad.

Anyway -- since there is runout with the collet, and still a
lack of parallelism to the spindle, check for burrs in the Morse taper
socket in the spindle. (Try spotting blue (Prussian blue) in a very
thin film on the Morse taper shank of the tool, then put it into the
socket lightly, twist a few degrees, and pull it back out. Check the
bluing for where it is rubbed off. If widely spread on one side, and in
a narrow location on the other side, then there is likely a burr in the
socket (which will need application of a Morse taper finishing reamer to
clean off). Or -- there *could* be a burr on the Morse taper arbor
instead -- patterns of blue built up around a clean spot could indicate
that, and require a little stoning to remove the burr. There could be
burrs on both the collet's arbor (assuming ER style collets) or the
individual collet (assuming a Morse taper collet).

I tried this with the chuck arbor MT3 taper. I got somewhat
inconsistent result but no large areas. Nothing I would want to attack
with abrasives remembering that I could screw things up rather than
help.

O.K.

I thought it would be helpful to check the run-out of the JT33 arbor
and tried to remove the chuck. I made a wooden jig to support it but
it seems that the helpful Chinese glued the thing in so I desisted
before things got out of hand.

The normal method for removing a chuck from an arbor is to use a
set of Jacobs chuck-removal wedges.

Check MSC part number 08592941 to see an example. (These are
for the #3 Jacobs taper. There are four different sizes depending on
the size of the Jacobs taper being removed -- and for some of them you
need two different sets to make a removal set for a particular size.
These are tapered in thickness (narrowest at the tips of the tines) and
are placed between the chuck and the shoulder of the Morse taper adaptor
from opposite directions, and are squeezed together with a vise. If the
Morse taper big end is smaller than the Jaobs taper in the chuck, you
may not have a shoulder to work against, and will have to destroy the
arbor by drilling a cross hole for a pin for the wedges to work against.

The MSC catalog page may list what combinations are needed for
what Jacobs tapers -- or it may be that I saw it on the Jacobs web
pages.

[ ... ]

6) The No. 3 center drill runs out at 0.008"

Weird.

7) The No. 4 at 0.007"

Again weird. This is in the chuck, or in the collet?

See above. I am beginning to think that the main problem is how this
chuck grips things in the jaws. I think it likes longer shanks. The
area between the flutes on the center drill is quite short. In a
collet it does not matter.

Jacobs style chucks are made to grip all the way down to the end
of the shank -- and if your tool won't seat fully back for whatever
reason, it will not be as good a grip, and the jaws may move in their
guides.

You might look at MSC item # 08592545 -- which is a rebuild kit
for some particular sizes of standard Jacobs chucks. (Replacement jaws
and replacement split threaded ring which feeds the jaws.) Since MSC's
web page has just gone offline, I can't tell more about it at the
moment. The best thing is to visit Jacobs' web site and read up on
rebuilding their chucks, then make the tools needed to press the chucks
apart and actually *see* how they work.

[ ... ]

1) Do not use digital indicators for this sort of work.

You had been using a digital one? I don't remember you saying
this. *Some* digital ones are more accurate than some mechanical ones.
The Starrett "Last Word" mechanical if the bias spring is not applying
bias throughout the range. (A bump on the side of the point can cause
it to skip in the spiral, so there is a major deadband in the range.)

I did the first time. It was a part of an existing set-up. They are
nice for some things, axis movement, measurements over 0.1", but for
this analog is better IMHO.

:-) A good analog one can read to a tenth of a thousandth.

2) Change the center drilling procedure as outlined above.
3) Grind a spotting drill?

How about *buy* at least one, so you know what it needs to look
like? I recently got (from a sale flyer from MSC) a couple of 1/4" x 60
degree spotting/centering drills (MSC #FJ71332167). If the sale from
that flyer is over, the "FJ" won't do any good, and the price will be
back up to whatever it was.)

Probably right. Getting the point exactly co-axial is probably
something I could not do with a Dremel.

Exactly co-axial with the spindle -- *sure* until you remove it
from the chuck. :-) But generating the flutes down to the point is a
major trick.


4) To locate cross lines on a work piece it seems preferable to use
optical punch first and then locate the center on the machine. This
probably makes center finder and spotting drill unnecessary and can be
done with a twist drill directly.

Probably -- especially with a drill with split points. For
larger standard bits, the chisel point may be wider than the dimple left
with the optical punch, in which case the drill is likely to walk away
from the punched center point.

In that case I would probably be drilling a smaller pilot hole anyway.

O.K.

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 ---

The MT pocket in the spindle is supposed to be accurately centered and
aligned to the spindle's centerline.
The wide end of the MT taper can be checked for concentricity with a dial
indicator, with an offset point or with a dial test indicator which allows
the point to be positioned for a reliable indication.
If the arbor MT socket isn't concentric with the spindle's centerline, this
would be the first point of inaccuracy.
As suggested earlier, the spindle bearings may contribute to runout errors.

In the exercise where an arbor is placed in the spindle, the machined
surfaces of the arbor should (ideally) also be centered and concentric.
If the arbor JT chuck taper isn't concentric with the spindle's centerline,
this would be the second point of inaccuracy.. chuck (in)accuracy isn't
involved yet.
Substituting an arbor is much easier than trying to regrind a JT taper, so
that's what I'd try if a particular arbor is introducing error, of say..
..002", because additional error can be expected from the chuck when it's
installed.
The earlier suggestion of making a light grind on the JT taper portion of
the arbor, should prove to be very concentric to the spindle centerline, at
least as accurate as the initial MT pocket runout test.

If the arbor has a tang, the arbor can be inserted in only 2 rotational
positions (approximately 180 degrees apart).
Placing a permanent mark on the spindle may be helpful in putting an arbor
back in the more accurate orientation.

When the chuck is installed, it will most likey involve some additional
inaccuracy.. a third point of inaccuracy.

Comments in a recent thread address chuck installation to an arbor.
"How Long Would You Leave It In The Freezer" 11-4

When the arbor is out of a machine with the chuck seated on the JT taper, I
generally place a drift in the chuck (end of drift in contact with the
internal end of the arbor, chuck only tightened loosely), and with the
chuck/drift pointing down, briskly wham/tamp/slam it on a very solid
surface.
The inertia breaks the taper's grip, and the arbor pops out of the chuck
taper. So far, I haven't needed to resort to the heat or dry ice methods.

The same force seats a chuck on an arbor very effectively, when the arbor is
removed from the machine (no drift required).
I generally tamp the arbor tang on a scrap of aluminum or brass, placed on a
very solid surface to seat the chuck JT taper.

--
WB
..........


wrote in message
...

I was thinking along those lines today and tried to remove the chuck
from its JT33 arbor to do the checking. It seems to be glued on.

This is where I get confused: What is an "excessive" error? Looking at
the Jacobs web-page their keyed chucks are guaranteed at best 0.003"
TIR, some considerably worse. I seem to be within this figure.

True. I suspect at some stage I shall have to accept that one cannot
make a silk purse out of a sow's ear :-)

However, going through this process has been helpful. At least I
understand better where the sources of error are and even managed to
reduce some of them with relatively simple adjustments.

Michael Koblic,
Campbell River, BC

In article ,
wrote:

On Fri, 12 Nov 2010 18:39:13 -0500, Joseph Gwinn
wrote:

[...]

What I do is to use an optical centering scope that mounts in the 3-jaw
or collet chuck of the spindle, followed by a large spotting drill.

http://www.use-enco.com/CGI/INSRIT?PMAKA=240-0404

I have found that with this scope, it's more accurate to not
center-punch the workpiece. I just center on the scribed lines and use
the spotting drill to make the initial dimple. A center-punch dimple
tends to pull the spotting drill sideways, reducing accuracy.

The other thing the scope is good for is locating zero-reference
features on a workpiece, subsequently using the DRO to move to places
where holes are desired. This is fast and accurate. I often scribe all
the hole centers, to catch errors, but again I don't center punch the
hole locations.

The only problem with the scope is that it was a bit expensive.


You are not kidding about the price, but wow, what a cool toy! I can
see that it would solve all sorts of problems.

All in all, I don't regret the purchase, despite the whining.


Then of course you are relying on the center drill being on the mark
which is something the OP questions :-)

The centering scope followed by a big (at least 3/8" diameter) spotting
drill and then by a stub drill is the best way I have found to get the
hole at the scribed location. If the location is off, oh well.

What is even more accurate is to use the DRO to locate a collection of
holes with respect to one another, but this process usually starts with
using the centering scope to set the DRO to a reference point on the
workpiece.


Another tool that comes to mind and which nobody mentioned is this:
http://littlemachineshop.com/product...=2604&category
=1310310429

I have heard conflicting opinions on it.

I have never used one of these. I didn't buy one because I could not
see how one could achieve 0.001" accuracy. Even if the laser beam focus
spot is that small on the workpiece, my eyes are not that good to tell
if the beam is exactly on the scribe marks. And I bet that the focal
spot is dazzlingly bright and scintillates.

The catalog pictures all show a laser-pointer beam, which would be
perhaps a millimeter in diameter (0.040" diameter), but the pictures may
be artistic versus technical.

My guess that in my hands, accuracy would be more like 0.005" to 0.010".
This is certainly good enough for woodworking.

With the centering scope, the limitations of my old eyes have little
effect on achievable accuracy, and I easily achieve 0.001", probably
less. This scope is how I discovered that the Millrite table gibs were
loose, when I saw the table cocking slightly when drive direction
reversed.

Joe Gwinn

On 13 Nov 2010 04:56:28 GMT, "DoN. Nichols"
wrote:

On 2010-11-13, wrote:
On 12 Nov 2010 06:01:52 GMT, "DoN. Nichols"
wrote:

My WML hates you. It swallowed your post again. OTOH it is not
prejudiced, it swallowed my last reply, too.

:-)

It knows that I do not trust Windows and reciprocates. :-)

This one it let through. The Forte Agent formats better. OTOH it has
other issues.

[ ... ]


I put the chuck back in. The dowel pin run 0.002 at "zero" and 4"! But
then I repositioned it slightly and re tightened and the wobble
appeared - 0.004" at 4".

Since you are using ER style collets -- you should be able to
cover the whole range that the chuck can hold (assuming a full set of
collets), so why not *use* the collets?

How do you drill a e.g. 7/64" hole with a collet? I guess start the
hole with a spotting drill in a collet and then switch the
arbors...OTOH if one has a proper spotting drill with a long enough
shank the procedure might not be necessary (see below). It certainly
seems the way to go if starting the hole with the center drills. Which
I won't 'cos I know better now.

I tried the center drills: No.3 was better initially at 0.003", but re
tightening I could make it 0.005".

No. 4 was 0.007"

For the sake of comparison I put the dowel pin in my drill press:
0.0035" and 0.007" at "zero" and 4".

How much could you move the stationary spindle by pushing
sideways on the chuck in various directions? Usually, the fit of the
quill to the headstock in a drillpress -- especially an import one --
can be pretty bad.

A fair bit.

[...]

I thought it would be helpful to check the run-out of the JT33 arbor
and tried to remove the chuck. I made a wooden jig to support it but
it seems that the helpful Chinese glued the thing in so I desisted
before things got out of hand.

The normal method for removing a chuck from an arbor is to use a
set of Jacobs chuck-removal wedges.

Check MSC part number 08592941 to see an example. (These are
for the #3 Jacobs taper. There are four different sizes depending on
the size of the Jacobs taper being removed -- and for some of them you
need two different sets to make a removal set for a particular size.
These are tapered in thickness (narrowest at the tips of the tines) and
are placed between the chuck and the shoulder of the Morse taper adaptor
from opposite directions, and are squeezed together with a vise. If the
Morse taper big end is smaller than the Jaobs taper in the chuck, you
may not have a shoulder to work against, and will have to destroy the
arbor by drilling a cross hole for a pin for the wedges to work against.

The MSC catalog page may list what combinations are needed for
what Jacobs tapers -- or it may be that I saw it on the Jacobs web
pages.

OK, what is wrong with my method?

1) Prop the chuck upside down on two blocks of wood by its shoulders
(where the wedges would go, too)
2) Open up the chuck to its widest.
3) Use an *aluminum* cylinder of a diameter just slightly less than
the diameter of the JT33 arbor through the open chuck jaws.
4) Hit with a BFH


[ ... ]


Jacobs style chucks are made to grip all the way down to the end
of the shank -- and if your tool won't seat fully back for whatever
reason, it will not be as good a grip, and the jaws may move in their
guides.

There is less than 3/4" of intact shank between the ends of the No. 4
center drill. The flutes start either side of it. This is enough for
the collet but clearly not enough for the chuck. It gets worse as the
center drill gets smaller. I think I mentioned that with the No. 1 it
is ridiculous. Never again No. 1 in a chuck!
..

You might look at MSC item # 08592545 -- which is a rebuild kit
for some particular sizes of standard Jacobs chucks. (Replacement jaws
and replacement split threaded ring which feeds the jaws.) Since MSC's
web page has just gone offline, I can't tell more about it at the
moment. The best thing is to visit Jacobs' web site and read up on
rebuilding their chucks, then make the tools needed to press the chucks
apart and actually *see* how they work.

Would they then work any differently on the center drills?



[ ... ]

1) Do not use digital indicators for this sort of work.

You had been using a digital one? I don't remember you saying
this. *Some* digital ones are more accurate than some mechanical ones.
The Starrett "Last Word" mechanical if the bias spring is not applying
bias throughout the range. (A bump on the side of the point can cause
it to skip in the spiral, so there is a major deadband in the range.)

I did the first time. It was a part of an existing set-up. They are
nice for some things, axis movement, measurements over 0.1", but for
this analog is better IMHO.

:-) A good analog one can read to a tenth of a thousandth.

What? You mean my $9 ones won't?

2) Change the center drilling procedure as outlined above.
3) Grind a spotting drill?

How about *buy* at least one, so you know what it needs to look
like? I recently got (from a sale flyer from MSC) a couple of 1/4" x 60
degree spotting/centering drills (MSC #FJ71332167). If the sale from
that flyer is over, the "FJ" won't do any good, and the price will be
back up to whatever it was.)

Probably right. Getting the point exactly co-axial is probably
something I could not do with a Dremel.

Exactly co-axial with the spindle -- *sure* until you remove it
from the chuck. :-) But generating the flutes down to the point is a
major trick.

Probably not worth the effort spending the time producing inferior
result. Fastenal show some US made ones. I shall see if the local
branch will sell me one (rather than a packet of 100).

Michael Koblic,
Campbell River, BC

On Fri, 12 Nov 2010 16:46:53 -0800, wrote:

On Fri, 12 Nov 2010 18:39:13 -0500, Joseph Gwinn
wrote:

[...]

What I do is to use an optical centering scope that mounts in the 3-jaw
or collet chuck of the spindle, followed by a large spotting drill.

http://www.use-enco.com/CGI/INSRIT?PMAKA=240-0404

I have found that with this scope, it's more accurate to not
center-punch the workpiece. I just center on the scribed lines and use
the spotting drill to make the initial dimple. A center-punch dimple
tends to pull the spotting drill sideways, reducing accuracy.

The other thing the scope is good for is locating zero-reference
features on a workpiece, subsequently using the DRO to move to places
where holes are desired. This is fast and accurate. I often scribe all
the hole centers, to catch errors, but again I don't center punch the
hole locations.

The only problem with the scope is that it was a bit expensive.


You are not kidding about the price, but wow, what a cool toy! I can
see that it would solve all sorts of problems.

Then of course you are relying on the center drill being on the mark
which is something the OP questions :-)

Another tool that comes to mind and which nobody mentioned is this:
http://littlemachineshop.com/product...y=131031042 9

I have heard conflicting opinions on it.

Michael Koblic,
Campbell River, BC

http://www.miketreth.mistral.co.uk/Hardware.htm

This is what I use...

http://www.penntoolco.com/catalog/pr...ategoryID=5873


Gunner
--
"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

On 2010-11-14, wrote:
On 13 Nov 2010 04:56:28 GMT, "DoN. Nichols"
wrote:

On 2010-11-13, wrote:
On 12 Nov 2010 06:01:52 GMT, "DoN. Nichols"
wrote:

My WML hates you. It swallowed your post again. OTOH it is not
prejudiced, it swallowed my last reply, too.

:-)

It knows that I do not trust Windows and reciprocates. :-)

This one it let through. The Forte Agent formats better. OTOH it has
other issues.

I wonder whether the WML is trying to do some spam blocking, and
interpreted something which I either posted or quoted as spam? I know
that the longer the incoming e-mail the greater the chance that my
Bayesian filtering will decide that it is spam -- and if it is also in
HTML, it is almost a certainty. (Since I don't read HTML with my e-mail
client (and am glad of that), I consider it unnecessary, and a source
of serious bloating in the messages. :-)

[ ... ]


I put the chuck back in. The dowel pin run 0.002 at "zero" and 4"! But
then I repositioned it slightly and re tightened and the wobble
appeared - 0.004" at 4".

Since you are using ER style collets -- you should be able to
cover the whole range that the chuck can hold (assuming a full set of
collets), so why not *use* the collets?

How do you drill a e.g. 7/64" hole with a collet? I guess start the
hole with a spotting drill in a collet and then switch the
arbors...

You said that they were ER style collets. ER stands for
"Extended Range" and most of the collets cover a 1mm range (e.g. 7-8mm,
and also marked with a range of fractional sizes).

These are unlike 5C collets, R8 collets and Morse taper collets
(which all have a very limited gripping size range), so your set should
have a collet which will include 7/64" in its range. Let's see -- 7/64"
is 0.1094", which is 2.7781 mm -- so look for a collet marked 2-3mm.
Some of my ER-25 collets at the small end switch to 0.5mm ranges, so you
may have to look for a 2.5-3.0 mm one depending on your set.

OTOH if one has a proper spotting drill with a long enough
shank the procedure might not be necessary (see below). It certainly
seems the way to go if starting the hole with the center drills. Which
I won't 'cos I know better now.

One of the advantages of spotting drills over center drills in
chucks is that they are not double-ended, so they bottom nicely in the
chuck.

I tried the center drills: No.3 was better initially at 0.003", but re
tightening I could make it 0.005".

No. 4 was 0.007"

For the sake of comparison I put the dowel pin in my drill press:
0.0035" and 0.007" at "zero" and 4".

How much could you move the stationary spindle by pushing
sideways on the chuck in various directions? Usually, the fit of the
quill to the headstock in a drillpress -- especially an import one --
can be pretty bad.

A fair bit.

Thus your measurements are limited by that.

[...]

I thought it would be helpful to check the run-out of the JT33 arbor
and tried to remove the chuck. I made a wooden jig to support it but
it seems that the helpful Chinese glued the thing in so I desisted
before things got out of hand.

The normal method for removing a chuck from an arbor is to use a
set of Jacobs chuck-removal wedges.

Check MSC part number 08592941 to see an example. (These are
for the #3 Jacobs taper. There are four different sizes depending on
the size of the Jacobs taper being removed -- and for some of them you
need two different sets to make a removal set for a particular size.
These are tapered in thickness (narrowest at the tips of the tines) and
are placed between the chuck and the shoulder of the Morse taper adaptor
from opposite directions, and are squeezed together with a vise. If the
Morse taper big end is smaller than the Jaobs taper in the chuck, you
may not have a shoulder to work against, and will have to destroy the
arbor by drilling a cross hole for a pin for the wedges to work against.

The MSC catalog page may list what combinations are needed for
what Jacobs tapers -- or it may be that I saw it on the Jacobs web
pages.

OK, what is wrong with my method?

1) Prop the chuck upside down on two blocks of wood by its shoulders
(where the wedges would go, too)
2) Open up the chuck to its widest.
3) Use an *aluminum* cylinder of a diameter just slightly less than
the diameter of the JT33 arbor through the open chuck jaws.
4) Hit with a BFH

Your method assumes that the chuck has a through hole to the
arbor socket. Most do not. Only the ones which are threaded onto
reversible electric drill motors are likely to have a through hole,
because they use a left-handed screw into the end of the spindle to keep
the drill chuck from unscrewing in reverse.

Now -- you *could* open the jaws fully, mount a drill bit
vertically in the mill vise (assuming that your vise has V grooves to
hold it firmly and vertically), center the chuck over that (using the
jaws to feel for the flutes and then retracting the jaws fully), and
then drill through the web.

But sometimes the way to remove a stuck arbor of the wrong size
from a chuck is to saw off the arbor, drill through *it* and tap for
zerk style grease fittings, and use a grease gun to fill the cavity with
grease and use the hydraulic pressure to pop the stub of the arbor out.
This would (obviously) not work with a through hole in the chuck body. :-)


[ ... ]


Jacobs style chucks are made to grip all the way down to the end
of the shank -- and if your tool won't seat fully back for whatever
reason, it will not be as good a grip, and the jaws may move in their
guides.

There is less than 3/4" of intact shank between the ends of the No. 4
center drill. The flutes start either side of it. This is enough for
the collet but clearly not enough for the chuck. It gets worse as the
center drill gets smaller. I think I mentioned that with the No. 1 it
is ridiculous. Never again No. 1 in a chuck!
.

While the spotting drills, since they are single ended, can use
the full length of the jaws for contact.

You might look at MSC item # 08592545 -- which is a rebuild kit
for some particular sizes of standard Jacobs chucks. (Replacement jaws
and replacement split threaded ring which feeds the jaws.) Since MSC's
web page has just gone offline, I can't tell more about it at the
moment. The best thing is to visit Jacobs' web site and read up on
rebuilding their chucks, then make the tools needed to press the chucks
apart and actually *see* how they work.

Would they then work any differently on the center drills?

Well -- I was not advising you to *purchase* the repair parts
set. Just look at the Jacobs web site to see how to take a chuck apart,
and then do so to show yourself how the chuck works. Then you can see
how a tool held only in the tips of the jaws will likely cause
deflection inside the chuck.

Since your chuck is of Chinese manufacture, the odds are they
they would not fit your chuck anyway -- metric dimensions instead of
inch dimensions are likely -- unless they are a total clone of Jacobs
chucks. (Note that some chucks from out of the country also have a
socket which is not a Jacobs taper -- but something similar with
different nomenclature, different dimensions, and perhaps even a
(slightly) different taper.)

[ ... ]

1) Do not use digital indicators for this sort of work.

You had been using a digital one? I don't remember you saying
this. *Some* digital ones are more accurate than some mechanical ones.
The Starrett "Last Word" mechanical if the bias spring is not applying
bias throughout the range. (A bump on the side of the point can cause
it to skip in the spiral, so there is a major deadband in the range.)

I did the first time. It was a part of an existing set-up. They are
nice for some things, axis movement, measurements over 0.1", but for
this analog is better IMHO.

:-) A good analog one can read to a tenth of a thousandth.

What? You mean my $9 ones won't?

What are the divisions on the scales? The ones which I am
talking about have divisions to 0.0001".

The small ones with the lever style contact point lose accuracy
unless the lever is at a specific angle. I think that is 30 degrees for
most, and at least one brand (no -- I don't remember which brand), is
accurate with the lever parallel to the work surface. To check what the
proper angle is for what you have, try different angles, and slide some
shim stock under the point to see if it moves the proper distance.

2) Change the center drilling procedure as outlined above.
3) Grind a spotting drill?

How about *buy* at least one, so you know what it needs to look
like? I recently got (from a sale flyer from MSC) a couple of 1/4" x 60
degree spotting/centering drills (MSC #FJ71332167). If the sale from
that flyer is over, the "FJ" won't do any good, and the price will be
back up to whatever it was.)

Probably right. Getting the point exactly co-axial is probably
something I could not do with a Dremel.

Exactly co-axial with the spindle -- *sure* until you remove it
from the chuck. :-) But generating the flutes down to the point is a
major trick.

Probably not worth the effort spending the time producing inferior
result. Fastenal show some US made ones. I shall see if the local
branch will sell me one (rather than a packet of 100).

It may be worth the trouble as a learning exercise, at least.
But as long as they are inexpensive enough, buying new is easier. :-)

Fastenal seems to have them -- and here is the part number of a
1/4" shank 1-1/2" long one: 7000098

And you are in luck -- it says "Package Quantity 1 (EA)" -- at least on
the web page. :-) They are saying "Wholesale Price: $6.63" which is more
than MSCs sales flyer price -- but if you can order it within Canada,
you don't have the brokerage problem which things shipped from the US to
Canada by UPS have.

Enjoy,
DoN.

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On 14 Nov 2010 05:19:16 GMT, "DoN. Nichols"
wrote:

On 2010-11-14, wrote:
On 13 Nov 2010 04:56:28 GMT, "DoN. Nichols"
wrote:

On 2010-11-13, wrote:
On 12 Nov 2010 06:01:52 GMT, "DoN. Nichols"
wrote:

My WML hates you. It swallowed your post again. OTOH it is not
prejudiced, it swallowed my last reply, too.

:-)

It knows that I do not trust Windows and reciprocates. :-)

This one it let through. The Forte Agent formats better. OTOH it has
other issues.

I wonder whether the WML is trying to do some spam blocking, and
interpreted something which I either posted or quoted as spam? I know
that the longer the incoming e-mail the greater the chance that my
Bayesian filtering will decide that it is spam -- and if it is also in
HTML, it is almost a certainty. (Since I don't read HTML with my e-mail
client (and am glad of that), I consider it unnecessary, and a source
of serious bloating in the messages. :-)

The news part of WML is completely different from the e-mail part and
behaves differently. There is no consistency. It has blocked two of
your posts and allowed two through. The same with my own!

I have yet to discover a spam filter on the e-mail side if only to
disable it. Permanently. I do not need it. I am still capable of
deciding what I do or do not want to read. Look what happens if you
allow the stupid machine to decide for you!

[ ... ]

These are unlike 5C collets, R8 collets and Morse taper collets
(which all have a very limited gripping size range), so your set should
have a collet which will include 7/64" in its range. Let's see -- 7/64"
is 0.1094", which is 2.7781 mm -- so look for a collet marked 2-3mm.
Some of my ER-25 collets at the small end switch to 0.5mm ranges, so you
may have to look for a 2.5-3.0 mm one depending on your set.

1/8, 3/16, 1/4, 5/16, 3/8, 1/2, 9/16, 3/4 (inches). I guess for 7/64
you would use 1/8"?

[...]

OK, what is wrong with my method?

1) Prop the chuck upside down on two blocks of wood by its shoulders
(where the wedges would go, too)
2) Open up the chuck to its widest.
3) Use an *aluminum* cylinder of a diameter just slightly less than
the diameter of the JT33 arbor through the open chuck jaws.
4) Hit with a BFH

Your method assumes that the chuck has a through hole to the
arbor socket. Most do not. Only the ones which are threaded onto
reversible electric drill motors are likely to have a through hole,
because they use a left-handed screw into the end of the spindle to keep
the drill chuck from unscrewing in reverse.

Now -- you *could* open the jaws fully, mount a drill bit
vertically in the mill vise (assuming that your vise has V grooves to
hold it firmly and vertically), center the chuck over that (using the
jaws to feel for the flutes and then retracting the jaws fully), and
then drill through the web.

But sometimes the way to remove a stuck arbor of the wrong size
from a chuck is to saw off the arbor, drill through *it* and tap for
zerk style grease fittings, and use a grease gun to fill the cavity with
grease and use the hydraulic pressure to pop the stub of the arbor out.
This would (obviously) not work with a through hole in the chuck body. :-)

I could swear I can see the bottom of the JT33 arbor through the chuck
(hence picking an aluminum bar with a smaller diameter). However, now
you have introduced doubt...


[ ... ]

:-) A good analog one can read to a tenth of a thousandth.

What? You mean my $9 ones won't?

What are the divisions on the scales? The ones which I am
talking about have divisions to 0.0001".

The small ones with the lever style contact point lose accuracy
unless the lever is at a specific angle. I think that is 30 degrees for
most, and at least one brand (no -- I don't remember which brand), is
accurate with the lever parallel to the work surface. To check what the
proper angle is for what you have, try different angles, and slide some
shim stock under the point to see if it moves the proper distance.

0.0005" is the best I can hope for.

[...]

Fastenal seems to have them -- and here is the part number of a
1/4" shank 1-1/2" long one: 7000098

And you are in luck -- it says "Package Quantity 1 (EA)" -- at least on
the web page. :-) They are saying "Wholesale Price: $6.63" which is more
than MSCs sales flyer price -- but if you can order it within Canada,
you don't have the brokerage problem which things shipped from the US to
Canada by UPS have.

Fastenal say many things on their web-site which do not necessarily
reflect reality up here. I shall give them a call.

Michael Koblic,
Campbell River, BC

On 2010-11-15, wrote:
On 14 Nov 2010 05:19:16 GMT, "DoN. Nichols"
wrote:

[ ... ]

I wonder whether the WML is trying to do some spam blocking, and
interpreted something which I either posted or quoted as spam? I know
that the longer the incoming e-mail the greater the chance that my
Bayesian filtering will decide that it is spam -- and if it is also in
HTML, it is almost a certainty. (Since I don't read HTML with my e-mail
client (and am glad of that), I consider it unnecessary, and a source
of serious bloating in the messages. :-)

The news part of WML is completely different from the e-mail part and
behaves differently. There is no consistency. It has blocked two of
your posts and allowed two through. The same with my own!

Well ... based on the e-mail headers, I have sent myself spam. :-)

They even forged the IP address of one of my mail servers as a
machine name (though the *real* IP address is captured by my e-mail
server anyway.)

I have yet to discover a spam filter on the e-mail side if only to
disable it. Permanently. I do not need it. I am still capable of
deciding what I do or do not want to read. Look what happens if you
allow the stupid machine to decide for you!

Indeed -- and not letting you select for yourself is even more
offensive.

[ ... ]

These are unlike 5C collets, R8 collets and Morse taper collets
(which all have a very limited gripping size range), so your set should
have a collet which will include 7/64" in its range. Let's see -- 7/64"
is 0.1094", which is 2.7781 mm -- so look for a collet marked 2-3mm.
Some of my ER-25 collets at the small end switch to 0.5mm ranges, so you
may have to look for a 2.5-3.0 mm one depending on your set.

1/8, 3/16, 1/4, 5/16, 3/8, 1/2, 9/16, 3/4 (inches). I guess for 7/64
you would use 1/8"?

Yes -- from a quick calculation, that is only 0.396mm larger, so
it should be within the range needed.

[...]

OK, what is wrong with my method?

[ ... ]

Your method assumes that the chuck has a through hole to the
arbor socket. Most do not. Only the ones which are threaded onto
reversible electric drill motors are likely to have a through hole,
because they use a left-handed screw into the end of the spindle to keep
the drill chuck from unscrewing in reverse.

[ ... ]

I could swear I can see the bottom of the JT33 arbor through the chuck
(hence picking an aluminum bar with a smaller diameter). However, now
you have introduced doubt...

Remember that the cavity is drilled (a shallow cone left by the
tip of the drill)-- along with three other holes at an appropriate angle
to hold the jaws.

If you are actually seeing the end of the arbor, it should be
flat with a center drill hole in the end, since the taper was ground
between centers.

[ ... ]

:-) A good analog one can read to a tenth of a thousandth.

What? You mean my $9 ones won't?

What are the divisions on the scales? The ones which I am
talking about have divisions to 0.0001".

[ ... ]

0.0005" is the best I can hope for.

O.K.

[...]

Fastenal seems to have them -- and here is the part number of a
1/4" shank 1-1/2" long one: 7000098

And you are in luck -- it says "Package Quantity 1 (EA)" -- at least on
the web page. :-) They are saying "Wholesale Price: $6.63" which is more
than MSCs sales flyer price -- but if you can order it within Canada,
you don't have the brokerage problem which things shipped from the US to
Canada by UPS have.

Fastenal say many things on their web-site which do not necessarily
reflect reality up here. I shall give them a call.

O.K.

Good luck with the purchase.

I would actually get two (I did actually get two from MSC) so
there is a spare if one gets the rather pointy tip broken.

Good Luck,
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 16 Nov 2010 00:00:30 GMT, "DoN. Nichols"
wrote:


[ ... ]



Indeed -- and not letting you select for yourself is even more
offensive.

At least the Forte Agent looks like it might do the job. Like anything
it needed a bit of tweaking but at least it does not miss posts and it
formats the replies properly. Probably worth $29.

[...]

If you are actually seeing the end of the arbor, it should be
flat with a center drill hole in the end, since the taper was ground
between centers.

That is what I *thought* I saw...


[...]

Fastenal say many things on their web-site which do not necessarily
reflect reality up here. I shall give them a call.

O.K.

Good luck with the purchase.

I would actually get two (I did actually get two from MSC) so
there is a spare if one gets the rather pointy tip broken.

Over the years I have made it a policy to have two of everything if
possible so yes, it will apply here too.

I was quite nervous when we sold our second car...

Michael Koblic,
Campbell River, BC

On 2010-11-16, wrote:
On 16 Nov 2010 00:00:30 GMT, "DoN. Nichols"
wrote:


[ ... ]



Indeed -- and not letting you select for yourself is even more
offensive.

At least the Forte Agent looks like it might do the job. Like anything
it needed a bit of tweaking but at least it does not miss posts and it
formats the replies properly. Probably worth $29.

I have heard good reports about it -- but I can't use it,
because I don't run Windows.

What I am using for usenet news is slrn. For e-mail mutt.

[...]

If you are actually seeing the end of the arbor, it should be
flat with a center drill hole in the end, since the taper was ground
between centers.

That is what I *thought* I saw...

It may be -- someone else may have drilled it out beforehand if
it is a second-hand chuck and arbor. Or -- the Chinese may do things
differently anyway. :-) I'll have to remember to check the inside of my
5/8" Jacobs "style" chuck which came with my drill press back in the
late 1970s.

[ ... spotting drills .... ]

I would actually get two (I did actually get two from MSC) so
there is a spare if one gets the rather pointy tip broken.

Over the years I have made it a policy to have two of everything if
possible so yes, it will apply here too.

Good!

I was quite nervous when we sold our second car...

I can imagine. When working on a car, it is always nice to have
a back-up car. :-)

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 16 Nov 2010 05:53:43 GMT, "DoN. Nichols"
wrote:


I have heard good reports about it -- but I can't use it,
because I don't run Windows.

Im running Mint Linux and Agent via Wine

Have been for years

Gunner

--
"Confiscating wealth from those who have earned it, inherited it,
or got lucky is never going to help 'the poor.' Poverty isn't
caused by some people having more money than others, just as obesity
isn't caused by McDonald's serving super-sized orders of French fries
Poverty, like obesity, is caused by the life choices that dictate
results." - John Tucci,

On 2010-11-16, Gunner Asch wrote:
On 16 Nov 2010 05:53:43 GMT, "DoN. Nichols"
wrote:


I have heard good reports about it -- but I can't use it,
because I don't run Windows.

Im running Mint Linux and Agent via Wine

Yes -- but Wine does not work on anything other than Intel based
systems. I'm using UltraSPARC based systems -- no Intel CPUs in them.

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 ---