Chuck jaw truing

[MrWhoopee]

Maybe I'm looking at this wrong.
The jaws are true. Not enough run out for the work I do.
Problem I'm having is the outer part of the jaw will not hold thin material.
I am trying to hold a thin tubing, with a mandrel for support.
Because the jaws don't hold all the way out, the tubing sometimes spins in the chuck.
This is why I think the jaws are not parallel when clamping towards the outside.
Does this make sense????

It's called bellmouth, and it's common enough that it has a name. The jaws/scroll have been tweaked/worn from clamping parts at the outer end. It may not be apparent unless the jaws are loaded (under pressure).

 

[abunai]

Bellmouth. Makes sense.
Question.....
Does it make a difference if I hold the jaws open at the bottom or top?????
I would think that if it's bellmouth, you would want to hold them open at the top.

 

[NortonDommi]

I've posted these before, an oldie but goodie.

 

[markba633csi]

I watched a YouTube recently where a guy was truing a Rockwell's 3 jaw by using some rubber pieces jammed in there- I wish I knew where the link
was

 

[ddickey]

Here you go.

 

[abunai]

That is interesting. I'll give it a try.

 

[abunai]

Haven't had time to work on it.
Need to make a jig to hold the grinder first.
Thinking of using a Dermel. But i don't know if the stone shank is long enough.
Any ideas????

 

[C-Bag]

There is a very knowledgeable gentleman named olderdan that posted this on another site for putting tension on the jaws to grind them true for curing bell mouth.

He made them for 3 jaw, and 4 jaw.


His cure for runout was .008" relief in the backplate register. I have yet to do the process as I'm still making the mount for Foredom grinder. But I believe this is the way I'll go when I get time to finish the mount.

 

[KBeitz]

I had to true up some new chucks for a business where I worked at.
I took 3/4" bearing stock and slathered it up with valve grinding compound.
I fixed the bearing stock so it could not turn and lightly tightened the
chucks jaws down on to it. I would turn the lathe one and let it run for
about one hour. It dd a great job. Make sure to disassemble the chuck
and wash out all the grinding compound when done.