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.RC.
01-30-2010, 11:42 PM
Is there any way to straighten lathe chuck jaws...

I recently purchased a new lathe, and while the lathe itself is impeccable the supplied chucks leave a lot to be desired.. I am trying to do some accurate work with the four jaw but it refuses to hold the work straight with the axis of the lathe

I dial in the piece to be worked upon only to then move the indicator to another section of the piece and it is wobbling all over the place..The jaws seem incapable of holding to work straight.

Any ideas of a fix.. Or is grinding the only solution??

Carld
01-30-2010, 11:47 PM
If it's a new lathe is there any chance of returning the chuck for a replacement? Are the jaws tight in the body?

.RC.
01-30-2010, 11:51 PM
The jaws are tight, but the chucks are chinese and probably within chinese specs..

Seems totally retarded to me to build a nice accurate machine then go and put the cheapest chucks you can find on it..

airsmith282
01-30-2010, 11:51 PM
if its a new lathe call the company or go see them wiht said chuck get a replacement one under warranty , if you mess with it you voied the warranty

MickeyD
01-31-2010, 02:25 AM
The problem that you have is very common, especially in older and worn equipment. http://homemetalshopclub.org/news/aug04/aug04.html has a nice article about 3/4 of the way down the page about using a die grinder to true up a 3 jaw chuck. If you don't have a die grinder a tool post grinder or even a stout dremel will work. I have trued up a couple of 3 jaw models this way and it works like a charm.

gda
01-31-2010, 02:52 AM
I just trued up the jaws on a 3-jaw chuck with a dremel flex shaft in a boring bar holder. I was worried about doing the job at first, but it came out great and was pretty easy.

Clamp in a piece of 1" cold rolled or a large drill shank and look for light around the jaws. My lathe would slowly walk the piece I was working out of the jaws unless I was using a tailstock.

But as others said if it is new - contact manufacturer first.

Forrest Addy
01-31-2010, 03:07 AM
Don't swallow the work. Few 4 jaw chucks have jaws whose gripping surfaces are warranted to be precisely oriented to the axis or radial plane. If you grip the work deep in the jaws its axis is sure to nutate and no amount of battering with a hammer will correct it for long.

Withdraw the work about 3/4 the length of the jaws so its gripped by the jaw tips. When the grip is short it may be a bit insecure but it's easy to tap the extended end into concentricity.

If the work is long and its surface can be scarred up sink the jaw serrations in it. If not you may have pad the jaws with copper or alumnum and rely on some form of outboard support like a center or a steady rest - maybe a cat head.

4 jaw chucks are usable even when worn to the point where the jaws rattle around like castenets as it's rotated by hand.

oldtiffie
01-31-2010, 03:36 AM
Is there any way to straighten lathe chuck jaws...

I recently purchased a new lathe, and while the lathe itself is impeccable the supplied chucks leave a lot to be desired.. I am trying to do some accurate work with the four jaw but it refuses to hold the work straight with the axis of the lathe

I dial in the piece to be worked upon only to then move the indicator to another section of the piece and it is wobbling all over the place..The jaws seem incapable of holding to work straight.

Any ideas of a fix.. Or is grinding the only solution??

Ringer.

Can you scana copy of your lathe chuck specifications and post them please?

There is a lot of latitude in lathe chuck specifications - by all makers - just some more than others.

Here are two 3-jaw specs for chucks that I have:
http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/3-jaw_chuck_specs1.jpg

http://i200.photobucket.com/albums/aa294/oldtiffie/Lathe_misc/3-jaw_chuck_specs2.jpg

I suggest that you run a similar set of tests on your chuck and see what the result is.

If it is outside the specs, I'd guess that you have a good case to go for a replacement chuck - if it is only the chuck.

I'd check the spindle flange on its own and then the back-plate/adaptor on the flange without the chuck on it and see how it stacks up.

A logical process should isolate the cause or causes.

.RC.
01-31-2010, 04:50 AM
Ringer.

Can you scana copy of your lathe chuck specifications and post them please?


Sorry, they went into the bin awhile ago...I usually keep all instruction manuals, but for the likes of consumable tooling I rarely bother...

I will do as forrest says and use a steady/centre..

John Stevenson
01-31-2010, 05:39 AM
Lathe chuck specs mean sht, they print those out and send them anyway.

If it's a new chuck it could be out, I was sent a batch of 4 jaw independent chucks that were running out to see if I could do anything with them. These were made in India and from a well know northern supplier in the UK.
Seemed well made, body ran true and you would think that was it on a 4 jaw?

The truth was the tenons / slots for the jaws had been machined on the piss, probably with the vertical axis of the machine not vertical.
This meant any bar set up would run true at the test point but wobble at any other.

I put a big bar in the TOS and took a skim, then clamped the chuck onto this bar reversed and clocked it up so it ran true at the rear.

When run the whole chuck was wobbling all over, I re skimmed the mounting face and register to true up but the register was now off spec.

I then remounted it on a new backplate and with the jaws out refaced the rest of the chuck.
This now gave me a working chuck with out of spec mountings.

I reported the fault to the dealer and cost to rectify and was told to scrap the whole shipment. I used the one I'd done on a MT4 taper for the tailstock of the TOS, one went on a welding positioner as it was [ accurate enough for that ]
One was bolted to a large piece of angle iron to act as a 4 jaw vise to be held in the bench vise, handy for working on castings.

The rest were given to friends for any of the above purposes.

.

Ron of Va
01-31-2010, 05:41 PM
You did not say what kind of mount your lathe has. FWIW

Be sure it is the jaws you are having trouble with. I had a similar problem on two occasions with a D1-5 mount. Once, I got a sliver of metal caught between the spindle and the mounting plate, which caused the work to wobble because the chuck would not pull up square. The second time, one of the bolts had backed out at the spindle and prevented the chuck from pulling up square.