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
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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.
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