Chuck Jaw Advice Please.

[aboard_epsilon]

Should I bother regrinding these in situ in the chuck ..with dremel in tool post.



They are out of this chuck that belongs to the South Bend 9a ...they cant hold anything strait ...they are miles out ..!!!



Here's a pic showing one compared with a good jaw out of its other small chuck



Here.... they are lined up so you can see what the last owner did ..



Is it acceptable to have dished jaws ...Will they hold the work right after sorting them out .

Is it worth trying to fix them and giving them even more of a dish ...

This is the only set of jaws it has ... it's a no make obscure chuck !

or

Is it not worth it ...buy a new chuck
What do you think guys .

all the best.markj

[Forrest Addy]

Grind them in place with a plug gripped in the master jaws to center things up. Couldn't hurt.

[SGW]

I'd give it a try. A lot cheaper than a new chuck, if it works.

You know about the need to "load" the chuck jaws the way they are when holding work, when you do the grinding, I assume....

Do you know the make of chuck? You might be able to buy a new set of jaws.

[aboard_epsilon]

YEP... know how to grind them ...well it will be my first time ..

but they will end up not like the good one from the other chuck ...and don't know if they will work the same gripping small or large ..

I'm justing asking if anyone has done grinding .,..to the extent that the whole of the jaw is dished with a 1/2 inch redius......and after been satisfied .

all the best.markj

[ptjw7uk]

You could also grind the 120 degree included angle so they would be near to the others jaws if you are so inclined.

Make a jig to grind the same of each side, might take some time but nothing to loose!

Peter

[SGW]

The radius may limit your ability to hold small-diameter work, I think. Other than that, I don't see a real problem with it...but then, I've never tried to use a chuck with jaws as worn as those.

[brian Rupnow]

I don't think that regrinding them to a radius will be that satisfactory. When holding anything with a smaller radius than the radius you grind them to, you will have a one point linear contact at each jaw. When holding anything larger , you will have a two point linear contact per jaw.

[aboard_epsilon]

I don't think that regrinding them to a radius will be that satisfactory. When holding anything with a smaller radius than the radius you grind them to, you will have a one point linear contact at each jaw. When holding anything larger , you will have a two point linear contact per jaw.

yep thats what i thought

build them up with weld ?

are they steel or cast iron ...if they are cast iron ...forget the welding

all the best.markj

[kmp]

yep thats what i thought

build them up with weld ?

are they steel or cast iron ...if they are cast iron ...forget the welding

all the best.markj

Mark, I had a set that looked similar to those on my first IXL lathe and after cleaning them up to a larger radius they never worked well for me. Although I tried to get the "flats" exactly the same height, one side of each jaw always contacted before the other. As my jaws were tight in their slots they didn't "equalize" and the variation in concentricity of the workpiece was large. After messing with them for some time I gave up and gave the chuck to a friend who had more patience. He found that the jaws were case hardened steel and he milled a slot down each jaw centre and silver soldered in a strip of steel (1/4" ish square) which he then reground to form the normal 120 deg angle. Even soft they worked OK for years on light work but I must admit I would not have had the patience - even if I had thought of the repair. If they are case hardened steel and I guess they might well be, then welding should be a reasonable option as long as you remove the hard "skin" to start with, of course with welding you will be able to re-case harden as well.

Regards

Keith

[Quetico Bob]

I don’t know about the gripping issue, my lathe come with a sprung 3-jaw, probably the first indication was someone tightened it so hard they broke ½ of one of the female key sockets off. Could not get anything less than .007 repeat no matter how many times I re-adjusted with a rubber mallet.

Got fed up and used a steel ring to expand the jaws tight at 3” ID ( my lathe has a 2-1/8 through hole) used a couple carbide edges on my index boring bar, took my time and cleaned them up. They were harder than the hubs of hell but it worked.
Not perfect, but if I spend some time I’m down to about .001.

But still, once mounted, I have to figure out how to complete before I un-chuck and on the other, I don’t have to waste to much of a 1” HR bar to clean up.

Cheers, Bob