On Mar 4, 2:44 pm, "Bob Daun" wrote:
I have used my chuck for quite awhile but I was just wondering why there is
a threaded hole in the back end of the adaptor (the side facing the
headstock when mounted). The threads in the hole are quite fine but there
is nothing in the hole. If I shine a flashlight into the hole I can see the
threads from my headstock. Is this meant to use as and additional hold
down? I would hesitate to do that as it would ruin the headstock threads.
Any thoughts on this?

--
Bob Daun

Bob,
Are there perhaps two threaded holes like you describe instead of only
one?
If so, these are used when you're removing the threaded insert. You
remove the screws (3) that are holding the insert in place, and thread
them through the threaded holes. Then you tighten them sequentially
to force the adapter to 'pop' out of the chuck body.
Tom Weber