Brian and I have a project cooking to make a lathe chuck backplate, to fit a new 4-jaw chuck onto the big lathe. The style we need, L0 (L-zero, picture here) has a keyway cut into it. We don’t have any way to do that.
Does anybody have a suitable broach? @carl.lance: I hear you have a shaper. Can it cut a 3/8" keyway?
In fact a shaper would be a great way to cut a broach. Ideal.
Unfortunately my shaper is completely disassembled for restoration…
I am willing to devote a couple of long days at the space (with help) to finish the restoration, but unless we do that it’s of little help…
Carl
Carl Lance
Oh, and I forgot to ask about the keyway dimensions. I do have a friend
with a set of broaches that may be available for loan… 
CARL