Got a "nice" LW dividing head today.

Cleaning it up, I found that it does have the inevitable one serious problem.

The chuck (1 1/2-8, apparently) is stuck, and isn't wanting to come off. Looks like it might have some rust in that area, although the rest of the "rust" was really just discolored and solidified grease or oil.

I have various concoctions for loosening rust, P'blaster, etc.

The question is how to apply force without risking damage to the worm setup. I don't think I want to pull the spindle if I don't have to, as it's not loose, seems OK. I'd have to take off the gear, and the rear nut, etc, which seems excessive....

I can set up on the spindle lock, but that doesn't seem to make it particularly any safer to reef on or "tunk" on the chuck (or on a piece of hex clamped in it, actually). I kinda need to get the chuck off for cleaning and/or disposal, I think its junk.

Not much spindle sticking out....

Ideas?