Hi Doug

I had the same problem with a chuck on my old McDougal lathe and I followed
Brown and Sharps instructions to lap the jaws flat again and it made all the
difference in the world. I will post the link to the thread if I can locate
it.

Bill D




"Doug Warner" wrote in message
...

Myford ML7, small 3-jaw chuck. No matter how tight I crank down on
it, pushing sideways on the end of a 8" bar will cause the bar to
shift, and the end to run untrue. Merely loosening and retightening
it will lose centering, at least at the far end.

Repairable, or do I have to buy a new chuck?

It's not the spindle bearing, since I don't see the same problem with
a smaller bar in a collet.

To reply, please remove one letter from each side of "@"
Spammers are vermin. Please kill them.

Before you give up on it, I'd do two things:

1. Disassemble, clean, grease and reassemble the chuck. There's an article
in HSM magazine on how to do this but nothing tough here. You wouldn't
believe the amount of swarf plugging everything up.

2. Theres a good chance your jaws have been whacked by a MAJOR shmuck. Look
at this site for how to retrue the jaws:
http://www.loganact.com/tips/chuck-jaw.htm

This would make make sence for what you're seeing. One or more jaws is
banana shape and not holding the entire length.

Karl

Hi Doug

I found the thread that I am sure has applicability to your problem. I
have posted the two messages that relate. The first describes the problem
that I had and the second outlines Brownsharp's solution that I followed.

Hope this solves your problem.

Bill D

**********************************************
Message 1 in thread
From: BillDarby )
Subject: Chatter while parting off a 5/8s rod


View this article only
Newsgroups: rec.crafts.metalworking
Date: 2000/08/09


Chatter while parting off a 5/8s rod.

I was parting off a 5/8 rod using my 10 inch MacDougall lathe and I
was getting an unbelievable amount of
chatter while doing so. I was using a 6 inch three jaw chuck on an L00
spindle. Everything was tight and the lathe
itself is very sturdy for the size of swing. The cutter was a .093" wide
tool, sharp, short, center height and an 1/8
of an inch from the face of the jaws.

When I supported the outboard end in a steady the lathe began to cut
the rod as if it were butter. (????)

I have had that lathe for some time but have never done any parting
on it that I can recall. The observation
that I dismissed the other day may have a great deal to do with this
problem. I was measuring the movement of the
carriage coming under load with a tenths indicator and at one point I had
the indicator on the spindle nose. At the same
time, I gave the back end of the spindle a push sideways. That spindle is 27
inches long and the push on the far end
caused a 2 tenths movement on the indicator on the nose.

Well that was a very fruitful trip out to the shop. I just slipped
out to confirm the 2 tenths reading and
also to see how much deflection I would get on the nose with me leaning on
an 14 inch rod in the chuck. Under a good
hefty load the indicator on the side of the chuck registered 5 tenths.

That did not seem to be enough to cause the chatter that I was
seeing. So I moved the indicator out to the one
inch SS rod that I had in the chuck and had it set "just" in front of the
jaws. Would you believe?? Ten ot twelve
thou movement in any direct ion that I pushed!!!!

I could not believe my eyes. When I looked close I could see a
sliver of light between the rod and the jaw
appearing and disappearing as I heaved on the bar. I thought perhaps the
jaws were moving in the chuck but when I
indicated to the jaws, none was moving more then the half thou that I found
the chuck itself to be moving.

So, when I began this post I had a suspicion that my spindle
bearings needed snugging up. Now I think that
the major problem is only that the face of the jaws have distorted into
something akin to a canoe shape and simply need
to be ground flat.

Some time ago someone stated that you could get enough load on your
jaws in order to grind them by running at
high RPM.
The best this lathe will do is 1550 RPM. Do you think that's high enough
to produce a good load?

A most profitable evening (morning).

Night all.

Bill Darby

BTW My apology to the spelling police for breaking my brake in a recent
post. It will not be the last. Darn spell
checker doesn't see errors like that.


**********************************************
Message 7 in thread
From: BillDarby )
Subject: Chatter while parting off a 5/8s rod


View this article only
Newsgroups: rec.crafts.metalworking
Date: 2000/08/09


Hello All

Well you are looking at one "very happy" dude. I used a 1.25 inch
brass rod two feet long with valve grinding pasteprepared, as per the
post in order to straighten my chuck jaws. I
have to say that it was an unqualified success! As soon as I cleaned the
paste from the chuck I chucked up anidentical piece piece of 5/8s stock and
the cutter literally fell through it. I could not crank the cross feed fast
enough tokeep up with the ease of cutting.Thank you brownnsharp!Bill
DarbyBTW The cutting speed was not 600 it was 460RPM.REF:Subject: how
do i check my spindle to see if it is true on mysheldon; Date:Fri, 28 Jul
2000 04:43:29 GMT;From:
**********************************************




"Doug Warner" wrote in message
...

Myford ML7, small 3-jaw chuck. No matter how tight I crank down on
it, pushing sideways on the end of a 8" bar will cause the bar to
shift, and the end to run untrue. Merely loosening and retightening
it will lose centering, at least at the far end.

Repairable, or do I have to buy a new chuck?

It's not the spindle bearing, since I don't see the same problem with
a smaller bar in a collet.

To reply, please remove one letter from each side of "@"
Spammers are vermin. Please kill them.

Doug Warner wrote:

Myford ML7, small 3-jaw chuck. No matter how tight I crank down on
it, pushing sideways on the end of a 8" bar will cause the bar to
shift, and the end to run untrue. Merely loosening and retightening
it will lose centering, at least at the far end.

Repairable, or do I have to buy a new chuck?

It's not the spindle bearing, since I don't see the same problem with
a smaller bar in a collet.

To reply, please remove one letter from each side of "@"
Spammers are vermin. Please kill them.

Use an indicator on the chuck body and each of the chuck jaws while you
try that push test. If they move, then either the chuck body isn't
seating right on the spindle or the jaws and their slots are well worn,
and you'd be better off replacing that chuck.

If the chuck and jaws stay put, then you probably need to true up the
contacting surfaces of the jaws, because they've probably become curved
through wear.

If you search around you'll find references on how to do that, including
how to support the jaws during the operation. You can dress them with a
Dremel tool with a rotary stone in it clamped to the toolpost, while the
chuck is rotating at a slow speed. That's what I've done more than once.

Jeff


--
Jeff Wisnia (W1BSV + Brass Rat '57 EE)

"If you can keep smiling when things go wrong, you've thought of someone
to place the blame on."

If all else fails..I have a "New Old Stock Myford" 3 jaw, and a 4 jaw
chuck, still in the greased wrappers, that I will be putting up for
sale, if someone can give me an idea what they normally sell for on
Ebay, etc etc.

Gunner

--
The problem with defending the purity of the English language is that
English is about as pure as a cribhouse whore. We don't just borrow words;
on occasion, English has pursued other languages down alleyways to beat
them unconscious and rifle their pockets for new vocabulary.
--James D. Nicoll

William G Darby wrote:

Hi Doug

I found the thread that I am sure has applicability to your problem. I
have posted the two messages that relate. The first describes the problem
that I had and the second outlines Brownsharp's solution that I followed.

Hope this solves your problem.

Bill D

**********************************************
Message 1 in thread
From: BillDarby )
Subject: Chatter while parting off a 5/8s rod


View this article only
Newsgroups: rec.crafts.metalworking
Date: 2000/08/09


**********************************************
Message 7 in thread
From: BillDarby )
Subject: Chatter while parting off a 5/8s rod


View this article only
Newsgroups: rec.crafts.metalworking
Date: 2000/08/09


Hello All

Well you are looking at one "very happy" dude. I used a 1.25 inch
brass rod two feet long with valve grinding pasteprepared, as per the
post in order to straighten my chuck jaws. I
have to say that it was an unqualified success!



[snip]






I'm afraid I can find no trace of theis posting! Can anyone suplly me with a copy?

thanks,

Dave

"spitfire2" I'm afraid I can find no trace of
theis posting! Can anyone suplly me with a copy?

thanks,

Dave

I did an advanced search on Google
http://www.google.com/advanced_group_search?hl=en

and entered the group (rec.crafts.metalworking) the author
(brownnsharp%40my-deja.com) and the word (brass) and this is the message
that
I selected is below.

Bill D



http://www.google.com/groups?q=brass...eja.com&rnum=1




From: )
Subject: how do i check my spindle to see if it is true on my sheldon
View: Complete Thread (10 articles)
Original Format
Newsgroups: rec.crafts.metalworking
Date: 2000/07/28

Take the chuck off. Put a dial indicator in the tapered hole and check
for runout. Shouldn't be any (.0002). Put a dead center in the
spindle. Put the dial indicator on the spindle. Shouldn't be any
runout. If there is any, turn the 60 degree taper until there isn't any.
Take the taper out and rotate it about 90 degrees and plug it back in.
Should still have no runout. If the runout has changed your spindle
taper isn't straight. Check the runout on the flat shoulder that the
chuck seats against (the shoulder perpendicular to the spindle, the
straight portion of the shoulder behind the threads isn't important.) If
runout is measurable, turn the shoulder slightly. Just shave it a
couple of tenths, until your tool is cutting all the way
around.(Pre-load the spindle slightly by pressing with the tailstock
while doing this!) Look at the chuck back plate and make sure there are
no dings in the area that seats against the shoulder. Scrapping or
lapping the back plate will get rid of dings without requiring the
surface be re-turned.
CLEAN the chuck. Take it apart and use carburetor cleaner and
brushes. Look at the scroll, to see if any wear is apparent. Use a
moto-tool with an abrasive disk to get rid of burrs on the gear teeth on
the scroll if they are worn badly. (I did this to an ancient Hardinge
chuck and was rewarded with a chuck that ran out less than .002 instead
of .008!) Lubricate the chuck as you assemble it. There should be less
than .001 inch of sideways play in the jaws.(perpendicular to the jaw's
slot. Check for runout at several clamp diameters. If the runout is
always in the same direction, then the jaws' faces can be ground to
correct the flaw, but only after you have carefully tested the
back-plate to make sure the surfaces which mate to the chuck body are
running true.
If you end up suspecting the jaw faces are wrong, then you can grind
them on the lathe to correct the flaw.
To grind the jaw faces, put a dead center in the spindle, and make
sure it is dead-on concentric and centered. Turn it true if you have
to. Take a brass rod about two feet long and put centers in both ends.
A rod about 1 inch in diameter would be appropriate. Make SURE the
tailstock is centered with the dead center in the headstock. Place the
rod between centers, with lubrication on the centers, and close the jaws
of the chuck down until they drag on the brass rod. Using a
screwdriver, put valve grinding compound on the brass rod where the jaws
touch the rod. Run the lathe at a slow (not back-gear)rate, and hold the
brass rod with the hand, so you can feel the torque being applied by the
jaws. Tighten the jaws slightly until you can barely keep the rod
from turning with your bare hands and grind a minute. Repeat several
times until a flashlight shows all jaws being ground from end to end.
Usually, one jaw will grind first, then another and finally all three.
Check the runout on your test rods. It is not unreasonable to get
within .001 runout on test rods near the same diameter as the brass
grinding rod. If other diameters test differently, then the scroll is
not centered around the spindle's center of rotation, or is just worn.
Note that the spindle has been ground with a round gripping surface
matching the O.D. of the brass rod. Diameters smaller than the brass rod
will grip correctly and be centered, but diameters larger will grip at
the outer edge of the curve and not necessarily grip correctly. Lapping
the jaws carefully to flatten the curve will help if this is a problem.



In article ,
(Asp3211968) wrote:
I have a sheldon lathe 111/4 swing. when i put stock in my three jaw
chuck.
it extends out about 2 or 3 inches. i index it to the chuck and it cuts
on one
side of the round stock. if i rotate it 180' it cuts on the opposite side
or
the same side as the original index mark and just on that one side. i
believe
eather my spindle is bent or my chuck has a problem. how would i check
this
and figure out what is wrong.



Sent via Deja.com http://www.deja.com/
Before you buy.

On Wed, 10 Sep 2003 14:42:14 -0700, Grant Erwin
wrote:



Your jaws might be bellmouthed. If that is the case you can try to
get new ones if they are standard or you can try grinding them -
you have little to lose!

If it's a Burnerd (standard Myford fitment) then new jaws are available....
They cost about the same as a new chuck :-(

Mark Rand
RTFM

In article , Doug Warner says...

I disassembled and cleaned it (before all these replies), and had
already re-ground the jaws by running a stone in the tailstock through
them. Upon close examination on the bench, they're still bellmouthed.

If the jaws have more than a thou or so of slop in the body
of the chuck, in the slots, as it sounds like from your
description of trying to stone them, it is most likely
trashed.

That is, if you can grasp them by hand and rock them
in an angular fashion so that one end moves more than
a thou, it's toast.

Jim

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