Bud wrote:
I'm trying to remove a 1/2" Jacobs chuck from a Milwaukee D handle
right angle drill. Milwaukee says to remove the 90 degree adapter w/
chuck, secure the nut behind the chuck, remove the reverse threaded
screw, insert largest allen wrench into chuck and whack the hell out
of it in the CCW direction. (jacobschuck.com says the same exact
thing)

This thing won't budge despite the whacks and I'm 100% certain I'm
doing it correctly. What is plan B when you have a stubborn chuck?
(penetrants, heat, alternating heat and cold, etc). I can't use too
much heat because right behind the chuck is a sealed bearing in the 90
degree elbow gear case.

If I do get this thing broken free should I use antiseeze compound to
prevent this from happening again?

I have used a soft faced hammer (urethane face) to remove these
chucks, often without a wrench on the shank.

Done by striking a glancing blow, on the side that results in
unscrewing the chuck off the mandrel.

Do whatever you have to, to secure the shank or mandrel in a vise,
then put the biggest hex key or stock that you can, into the chuck (1/2
inch) and get a wrench onto it. An impact would work. A little heat
might help, as dried old oil may have varnished it in place.

Cheers
Trevor Jones