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View Full Version : Lathe Chuck Jaws and Truing Widgets?



CCWKen
11-28-2006, 08:37 PM
What do they call those jaw holders used for truing/grinding chuck jaws? The ones that look like Klingon Yard Darts. I found some NOS 2-piece jaws for my old Bison but they need some "fine tuning". Anyone have one that will fit a 6 1/4" chuck?

Or would making a tube to expose the jaws be better?

JCHannum
11-28-2006, 09:01 PM
If it is a two piece jaw, grip a round in the master jaws and allow the top jaws to stand clear of it. Then you can lightly grind the top jaws to true them.

CCWKen
11-28-2006, 09:36 PM
I did that initially but now I have the reversables about .0015 smaller than the masters. It works great except when I need to through-hole the stock. I need to true the masters and the reversables at the same time to ensure they're the same size. Then do the ID clamp surfaces too.

Mark Hockett
11-28-2006, 09:38 PM
The way JCHannum described doing it is a good way to true the jaws. I will just add an easy way to get a round object into the master jaws. Find a socket about the diameter you want to use. Put the socket on an extension and stick it in the chuck deep enough for the master jaws to clamp on it, tighten the chuck and remove the extension. When your done just stick the extension back in the socket, loosen the chuck and remove.

CCWKen
11-28-2006, 09:48 PM
I guess I should have mentioned this is a complete new set. Masters and reversables (two-piece).

JCHannum
11-28-2006, 09:54 PM
You can do the master jaws separately. Make a ring with a center hole or thin slice of large OD heavy wall tubing or pipe, and use the bolts for the jaws to grip it. Then dress the master jaws.

Ideally, the top jaws should overhang the master jaws slightly when all is done to ensure that they are doing the gripping.

CCWKen
11-28-2006, 10:13 PM
You can do the master jaws separately. Make a ring with a center hole or thin slice of large OD heavy wall tubing or pipe, and use the bolts for the jaws to grip it. Then dress the master jaws.

Brilliant!


Ideally, the top jaws should overhang the master jaws slightly when all is done to ensure that they are doing the gripping.

I wasn't aware of that. Thanks. What's the purpose of having jaw faces on the masters? If they were matched, wouldn't the grip force be better? Or just spread out?

JCHannum
11-28-2006, 10:20 PM
The master jaws may or may not be finished to grip work. It depends on the chuck and/or manufacturer. If they are finished, they can be used alone for gripping thin sections.

Be sure to number the top jaws.

wierdscience
11-28-2006, 10:24 PM
Both jaws should be ground the same,it's the way they leave the factory,I was told this is to prevent bell mouthing which sounds reasonable.

CCWKen
11-28-2006, 11:00 PM
Thanks guys! I think I'll use Jim's ring technique on some extended studs/nuts in place of the outer cap screws and do both jaws at the same time. I needed an excuse to go to the salvage yard anyway. Lots of large pipe there. I should be able to find various sizes to do the ID surfaces too. (Clamp, do one step, shift size, do another step.)

Yes Jim, these are matched and numbered as a set. They were just off a tad when I put them in my chuck.