Craftsman 4 Jaw Chuck Screw

[wa5cab]

You could try brazing or welding it back on. It doesn't appear that you have anything to lose, other that a little time.

 

[whitmore]

Once you get down to trying to make a replacement, don't discard making a two piece solution. Figure out how to cut the thread.

Then make a separate piece with a square hole and silver braze it to the threaded piece.

This outfit can supply the hole...
<http://www.sturdybroaching.com/contact-us-2>
if the threading isn't a problem. Until then, a four jaw chuck with three working
jaws isn't a lot of fun.

Making four screws, and switching out the square-drive key for a hex tip,
you could just braze Allen screws (big 'uns) into tapped holes. Or use threadlock.

I can't imagine how the original could break, and still be un-stretched enough to
take a braze-together fix.

 

[cathead]

A repair using silver solder might be a viable option for you. I fixed a chuck jaw that way and it works fine.
Silver solder is great for these kinds of repairs because of its high tensile strength. I wouldn't even consider
using brass(braze) for a repair like that knowing that silver solder has two to three times the tensile strength.

 

[cbrims]

I have to see how the broken piece fits into the screw, if it feels like it seats nicely, I'll look into what it's going to take for silver soldering. Otherwise I'll go back to my original option of making a new one. I still need to build a tool to remove the plug that holds the screw in from the back.