Found something that works. Y'all tell me if I am screwing up. I have
found that if I hit the jaws with a plastic faced hammer while I am
tightening my chuck I can get every bit of the runout out. Thinking
back, I've seen my friend and full time machinist do the same thing on
both three jaw and four jaw chucks. Is this a standard practice or am
I damaging my chuck?

Chuck is a new Chinese that came on my new Precision Matthews 13X40.
Spindle face runs true as does the chuck body itself as long as the
chuck is mounted in the same position every time. D1-4 mount. Never
had these problems on my old Sheldon 11 X42 but it was a well worn
machine of 1942 vintage

"Gerry" wrote in message
...
Found something that works. Y'all tell me if I am screwing up. I have
found that if I hit the jaws with a plastic faced hammer while I am
tightening my chuck I can get every bit of the runout out. Thinking
back, I've seen my friend and full time machinist do the same thing on
both three jaw and four jaw chucks. Is this a standard practice or am
I damaging my chuck?

Chuck is a new Chinese that came on my new Precision Matthews 13X40.
Spindle face runs true as does the chuck body itself as long as the
chuck is mounted in the same position every time. D1-4 mount. Never
had these problems on my old Sheldon 11 X42 but it was a well worn
machine of 1942 vintage

I'm guessing you must be talking about a lathe. I know a long time ago a
guy who worked for me showed that no matter how hard you muscle the key in a
hammer drill the chuck will vibrate loose when you are hammering a hole in
concrete or hard brick, but if you go around the chuck tightening as hard as
you can at all three holes it takes out the play in the mechanism and it
holds a lot better. Can't say if you are damaging a chuck this way or not,
but I know it worked, and the chucks on our drills usually outlasted the
motors as hard as we used them. (Now I have a couple Spline-Drive and SDS
rotary hammers for this type work.)

Bob La Londe
www.YumaBassMan.com

On Wed, 16 Jul 2008 08:04:01 -0700 (PDT), Gerry
wrote:

Found something that works. Y'all tell me if I am screwing up. I have
found that if I hit the jaws with a plastic faced hammer while I am
tightening my chuck I can get every bit of the runout out. Thinking
back, I've seen my friend and full time machinist do the same thing on
both three jaw and four jaw chucks. Is this a standard practice or am
I damaging my chuck?

Chuck is a new Chinese that came on my new Precision Matthews 13X40.
Spindle face runs true as does the chuck body itself as long as the
chuck is mounted in the same position every time. D1-4 mount. Never
had these problems on my old Sheldon 11 X42 but it was a well worn
machine of 1942 vintage
Greetings Gerry,
Consider just the chuck itself and not how it mounts to the spindle.
Inside is a scroll plate which is centrally located by its bore. This
bore must be a close fit on the register in the chuck body itself in
order for the chuck to repeat. The jaws are located by the scroll.
This means that the scroll, which is a spiral, must be machined
accurately and on center with the bore in the scroll plate in order
for the chuck as a whole to repeat. If the jaws and their associated
scroll sectors are machined accurately then they should repeatedly
chuck parts on center. When the chuck is tightened the scroll plate
is subjected to offcenter loading which will tend to push it against
the side of the bore in the scroll plate. If the bore isn't a close
fit the scroll will shift off center. So hammering on the jaws may be
shifting the scroll back to center. It's also possible that there is
dirt in the scroll and chuck body that is shifting around. Your best
bet is to take apart the thing, clean all parts well, and measure the
clearances. Then you can determine what is really going on. Think
about this: it's possible that if hammering on the jaws brings the
part on center then cutting forces may push the part off center. Then
it will be really hard to decide what exactly is happening.
Eric

Gerry wrote:
Found something that works. Y'all tell me if I am screwing up. I have
found that if I hit the jaws with a plastic faced hammer while I am
tightening my chuck I can get every bit of the runout out. Thinking
back, I've seen my friend and full time machinist do the same thing on
both three jaw and four jaw chucks. Is this a standard practice or am
I damaging my chuck?

No, your chuck is already damaged! The jaw slots must be loose
already. My new Phase-II chuck had jaws so tight that you could
not move them by hand, when new. They are still a VERY snug
fit, although they have loosened up enough that you can move
them across the backlash in the scroll teeth by hand, now.

You may want to at least screw the jaws all the way out of the
body and clean the scroll teeth with a rag and re-oil. There
may be a lot of grinding grit in there. Make sure you get the
jaws back in the same slot they came out of. If these are
2-piece jaws, you should remove the top jaws and clean under
them, too.

Jon

On Wed, 16 Jul 2008 08:04:01 -0700 (PDT), Gerry
wrote:

Found something that works. Y'all tell me if I am screwing up. I have
found that if I hit the jaws with a plastic faced hammer while I am
tightening my chuck I can get every bit of the runout out. Thinking
back, I've seen my friend and full time machinist do the same thing on
both three jaw and four jaw chucks. Is this a standard practice or am
I damaging my chuck?

Chuck is a new Chinese that came on my new Precision Matthews 13X40.
Spindle face runs true as does the chuck body itself as long as the
chuck is mounted in the same position every time. D1-4 mount. Never
had these problems on my old Sheldon 11 X42 but it was a well worn
machine of 1942 vintage


Years ago, when I was an apprentice, we were taught that no chuck ran
true. If you wanted a specific part to run really true you set it up
on either a face plate or a four jawed chuck and then indicated it.

In fact, once you made the first cut on a piece in a three jawed chuck
you might remove the entire chuck and work but you never removed the
work from the chuck.

Bruce-in-Bangkok
(correct Address is bpaige125atgmaildotcom)

On Wed, 16 Jul 2008 23:11:37 GMT, wrote:

On Wed, 16 Jul 2008 08:04:01 -0700 (PDT), Gerry
wrote:

Found something that works. Y'all tell me if I am screwing up. I have
found that if I hit the jaws with a plastic faced hammer while I am
tightening my chuck I can get every bit of the runout out. Thinking
back, I've seen my friend and full time machinist do the same thing on
both three jaw and four jaw chucks. Is this a standard practice or am
I damaging my chuck?

Chuck is a new Chinese that came on my new Precision Matthews 13X40.
Spindle face runs true as does the chuck body itself as long as the
chuck is mounted in the same position every time. D1-4 mount. Never
had these problems on my old Sheldon 11 X42 but it was a well worn
machine of 1942 vintage
Greetings Gerry,
Consider just the chuck itself and not how it mounts to the spindle.
Inside is a scroll plate which is centrally located by its bore. This
bore must be a close fit on the register in the chuck body itself in
order for the chuck to repeat. The jaws are located by the scroll.
This means that the scroll, which is a spiral, must be machined
accurately and on center with the bore in the scroll plate in order
for the chuck as a whole to repeat. If the jaws and their associated
scroll sectors are machined accurately then they should repeatedly
chuck parts on center. When the chuck is tightened the scroll plate
is subjected to offcenter loading which will tend to push it against
the side of the bore in the scroll plate. If the bore isn't a close
fit the scroll will shift off center. So hammering on the jaws may be
shifting the scroll back to center. It's also possible that there is
dirt in the scroll and chuck body that is shifting around. Your best
bet is to take apart the thing, clean all parts well, and measure the
clearances. Then you can determine what is really going on. Think
about this: it's possible that if hammering on the jaws brings the
part on center then cutting forces may push the part off center. Then
it will be really hard to decide what exactly is happening.
Eric
In my mind, beating on the jaws will greatly facilitate over
tightening the chuck with resultant distortion of the scroll.
Gerry :-)}
London, Canada

wrote:
On Wed, 16 Jul 2008 08:04:01 -0700 (PDT), Gerry
wrote:


Found something that works. Y'all tell me if I am screwing up. I have
found that if I hit the jaws with a plastic faced hammer while I am
tightening my chuck I can get every bit of the runout out. Thinking
back, I've seen my friend and full time machinist do the same thing on
both three jaw and four jaw chucks. Is this a standard practice or am
I damaging my chuck?

Chuck is a new Chinese that came on my new Precision Matthews 13X40.
Spindle face runs true as does the chuck body itself as long as the
chuck is mounted in the same position every time. D1-4 mount. Never
had these problems on my old Sheldon 11 X42 but it was a well worn
machine of 1942 vintage

Greetings Gerry,
Consider just the chuck itself and not how it mounts to the spindle.
Inside is a scroll plate which is centrally located by its bore. This
bore must be a close fit on the register in the chuck body itself in
order for the chuck to repeat. The jaws are located by the scroll.
This means that the scroll, which is a spiral, must be machined
accurately and on center with the bore in the scroll plate in order
for the chuck as a whole to repeat. If the jaws and their associated
scroll sectors are machined accurately then they should repeatedly
chuck parts on center. When the chuck is tightened the scroll plate
is subjected to offcenter loading which will tend to push it against
the side of the bore in the scroll plate. If the bore isn't a close
fit the scroll will shift off center. So hammering on the jaws may be
shifting the scroll back to center. It's also possible that there is
dirt in the scroll and chuck body that is shifting around. Your best
bet is to take apart the thing, clean all parts well, and measure the
clearances. Then you can determine what is really going on. Think
about this: it's possible that if hammering on the jaws brings the
part on center then cutting forces may push the part off center. Then
it will be really hard to decide what exactly is happening.
Eric

All the 3 jaw chucks I have, 4 in total, have a master pinion marked
with a 0 next to it. Tightening with that pinion gives the truest
running of the part. This is due to the tightening taking up the very
small clearance between the scroll and its locating part.