Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work.

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Steve
 
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Default Backplate stuck on 8" 3 Jaw chuck???

I have a 8" 3 jaw chuck that I got with my Sheldon. It is rusted and I
cannot see any marking on it anywhere. I also cannot see any markings
on the jaws or the body of the chuck that advise which jaw goes where.
The problem is I chucked up a piece of round stock and it had over
..015 runout. I then got a piece of drill rod and it was the same. That
is of course unacceptable. So I checked the spindle run out and it is
in the area of .0005. I believe that is mainly due to the vibration of
the lathe. The thread on the spindle amd the backplate is a 2.25"x8.

So I took all of the allen head bolts out to seperate the backplate
from the chuck so I could check the runout of the backplate. There
were 6 bolts around the outside and 6 bolts around the inside where
the through hole is located in the chuck. The backplate will not come
off. I tried a deadblow hammer. I tried a cold chisel to try to
seperate the two and I tried WD40 to try to break it loose. It did not
budge. Any suggestions on how to get the back plate off? I kicked
around the idea of making a dummy spindle and threading it. Then screw
it into the backplate and give it a whack with the deadblow. Only
problem is I don't have any stock that big right now. Any other ideas
greatly appreciated. Thanks, Steve
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DoN. Nichols
 
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Default Backplate stuck on 8" 3 Jaw chuck???

In article ,
Steve wrote:
I have a 8" 3 jaw chuck that I got with my Sheldon. It is rusted and I
cannot see any marking on it anywhere. I also cannot see any markings
on the jaws or the body of the chuck that advise which jaw goes where.


Hmm ... I've seen chucks with the jaw slot numbers in the bottom
of the slots at the outside diameter. You can't see them until the
jaws are removed.

And I've seen jaws with the numbers in the bottom of the way
grooves in the sides -- again, you can't see them while the jaws are in
the chuck. Also, if there is a flat on the bottom of the jaws clear of
the threads to engage the scroll, that might hold the jaw numbers.

The problem is I chucked up a piece of round stock and it had over
.015 runout. I then got a piece of drill rod and it was the same. That
is of course unacceptable.


Hmm ... a really beat up old chuck might be that bad. Or it
might not. Have you tried using different sockets to do the final
tightening? On a worn chuck, this can make a difference, as can
shimming the ID of the scroll plate so it can't slide around as much
inside the chuck body.

Also -- as a final thing, if there truly are no markings
anywhere. Paint a set of numbers on the body of the chuck, and a set of
letters on the chuck jaws. Remove them, and replace them one slot
clockwise from where they were. Measure the runout. Then repeat by
moving them to slots two from where you started, and measure that. Once
you find the position which give the minimum runout, mark the slots and
the jaws, so you can use the same slots in the future.

Or -- when you get it to a minimum which is still not good
enough, put in spacers to allow you to load the jaws while having access
to the tips, and use a toolpost grinder to true the jaws -- taking care
to protect the rest of the lathe from the grinding swarf, and plan to
disassemble and clean up the chuck after you finish the work.

So I checked the spindle run out and it is
in the area of .0005. I believe that is mainly due to the vibration of
the lathe. The thread on the spindle amd the backplate is a 2.25"x8.

So I took all of the allen head bolts out to seperate the backplate
from the chuck so I could check the runout of the backplate. There
were 6 bolts around the outside and 6 bolts around the inside where
the through hole is located in the chuck.


Hmm ... that sounds strange. Are there also four Allen-head
setscrews near the back of the chuck in the sides? If so, this may be
an adjust-tru style of chuck, and you can tune the runout for a given
size.

The backplate will not come
off. I tried a deadblow hammer. I tried a cold chisel to try to
seperate the two and I tried WD40 to try to break it loose. It did not
budge. Any suggestions on how to get the back plate off? I kicked
around the idea of making a dummy spindle and threading it. Then screw
it into the backplate and give it a whack with the deadblow. Only
problem is I don't have any stock that big right now. Any other ideas
greatly appreciated. Thanks, Steve


I have seen chucks with extra holes in the backplate which are
threaded, and accept the same thread screws which hold the backplate to
the chuck. Place the screws in the threaded holes, and bring them down
until they bottom on the chuck body. Then tighten them a quarter turn
at a time to jack the backplate away from the chuck's body.

Of course -- if this chuck is badly enough worn, you may be
ahead of the game to buy a new chuck -- Bison seems to be a good
compromise between price and quality -- I'm very happy with the one
which I got for my Clausing.

Of course -- with any 3-jaw chuck without the adjust-tru feature
added, you'll never get truly no runout -- except with soft jaws bored
to fit the workpiece for a specific job.

Good Luck,
DoN.
--
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 ---
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Gunner
 
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Default Backplate stuck on 8" 3 Jaw chuck???

On 8 Oct 2003 18:01:56 -0700, (Steve) wrote:

I have a 8" 3 jaw chuck that I got with my Sheldon. It is rusted and I
cannot see any marking on it anywhere. I also cannot see any markings
on the jaws or the body of the chuck that advise which jaw goes where.
The problem is I chucked up a piece of round stock and it had over
.015 runout. I then got a piece of drill rod and it was the same. That
is of course unacceptable. So I checked the spindle run out and it is
in the area of .0005. I believe that is mainly due to the vibration of
the lathe. The thread on the spindle amd the backplate is a 2.25"x8.

So I took all of the allen head bolts out to seperate the backplate
from the chuck so I could check the runout of the backplate. There
were 6 bolts around the outside and 6 bolts around the inside where
the through hole is located in the chuck. The backplate will not come
off. I tried a deadblow hammer. I tried a cold chisel to try to
seperate the two and I tried WD40 to try to break it loose. It did not
budge. Any suggestions on how to get the back plate off? I kicked
around the idea of making a dummy spindle and threading it. Then screw
it into the backplate and give it a whack with the deadblow. Only
problem is I don't have any stock that big right now. Any other ideas
greatly appreciated. Thanks, Steve


close the jaws gently around a chunk of pipe or bar stock, that will
fit in the chuck, but touch the back plate (some chucks will allow this,
others will not. Then bang the pipe straight down on a nice chunk of
plate steel on your floor. Repeat as necessary.

There IS a possibility that you have two jaws out of place, but
generally that will show more than .015 TIR... more like .1 or more.

Gunner
Cum catapultae proscriptae erunt tum soli proscript catapultas habebunt.
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