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Can you clean up jaws using a boring bar?

slimpick

Plastic
Joined
Nov 4, 2023
Location
Detroit, MI
I noticed the jaws on this chuck have imperfections - chips stuck in them, etc. Is there a way to hold the jaws rigid and then lightly run a boring bar down them to give them a new finish? I suppose one would need to do this at a larger diameter than what you want to hold. ??? or maybe there is some technique. ???

And yes this is supposed to be a 6 jaw chuck - but the other 3 jaws are missing. No one can seem to be able to find them.
 

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You can... one way is to clamp on a known round slug/ring with the master jaws just inside the chuck body, then touch-up the top jaws. It works in a pinch to remove a bit of bell-mouth, etc. The jaws on my Buck are pretty hard and I ended up using a sharp endmill as a boring bar which worked very well. more difficult is re-cutting the serrations if that's needed too. Grinding, as mentioned above, is better.
 
I noticed the jaws on this chuck have imperfections - chips stuck in them, etc. Is there a way to hold the jaws rigid and then lightly run a boring bar down them to give them a new finish? I suppose one would need to do this at a larger diameter than what you want to hold. ??? or maybe there is some technique. ???

And yes this is supposed to be a 6 jaw chuck - but the other 3 jaws are missing. No one can seem to be able to find them.
The reason 3 jaws are missing is that a 6 jaw chuck is fairly useless on anything but thin wall tubing that will flex a bit when tightened allowing each jaw to do roughly the same amount of work. A 6 jaw chuck is really a 2 jaw chuck most of the time. A slightly out of round bar will only grip on 2 opposite jaws. as far as boring them if there is any wear on the scroll you will end up with a chuck that is accurate at that diameter and miles out everywhere else.
 
FWIW, I've never liked methods that give a curved gripping surface. I measure my runout and then correct the jaws in the surface grinder. Works great if you do it right, assuming the jaws aren't loose in the chuck body, IOW, don't tilt when clamped.
 
the problem with propping the jaws open is that you will be using the opposite side of the scroll to the side used to close the jaws. After some wear, both sides of the scroll will be different. Which clamping direction do you want the jaws to be accurate to?
 
the problem with propping the jaws open is that you will be using the opposite side of the scroll to the side used to close the jaws. After some wear, both sides of the scroll will be different. Which clamping direction do you want the jaws to be accurate to?
You won't be using the opposite side if you use an external spider that clamps on the screws, or if you prop the master jaws. If you prop the master jaws it doesn't work uite as well because the jaws won't tilt as they do in normal operation.
 
Turned a sleeve to just fit chuck bore.
Cut segments to fit between jaws.
Bored it

Nothing I do ever works,
But THIS WORKED! Worked GREAT,
Beauty, no runnout!1704255181444.jpeg
 
The problem with clamping a ring and grinding the jaws is that you may end up with off-center jaws. i.e. the jaws will grip on-center only when they happen to be holding something the same size that they were ground to. To avoid that problem, you need to trust that the original manufacture of the chuck aligned the slots for the jaws to the center of the chuck body. So first step, before you grind the jaws is to center the chuck body on axis (assuming you have an adjust-tru style chuck).
 
Drill the face of the jaws for a small dowel. Then you can put your preload ring on the face of the jaws and bore through uninterrupted. You can also windage the cutter a little bit as you bore to the rear. Maybe .001/1" for a decent chuck, up to maybe .003/1" or more on a worn out chuck.
 








 
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