I guess the good news is that if tapers are that well locked, there
probably isn't any scoring on the taper surfaces, maybe.

I've released some stubborn chucks and other parts by using a drift,
then tamping the assembly down on a hard surface.
The drift would just be a section of mild steel that is capable of
passing thru the hole at the back of the chuck cavity.
A 6" to 12" piece of round stock inserted into the chuck with the jaws
loosely adjusted to the round stock (so the jaws can slipalong the
stock).

A good set of gloves should protect your hands from injury. With the
chuck opening pointed down, and with the weight of the chuck and arbor
resting on the drift, raise it in the air over a solid mass, then tamp
down hard, allowing the force to be transmitted thru the drift to the
inner end of the arbor taper.

If a few solid tamps don't release the taper lock, some bad voodoo is
going on in there, requiring the steady pressure of a press.

WB
...............

xray wrote:
I have a Jacobs 14N 1/2" chuck for the tailstock of my lathe. The MT2
arbor it is mounted on has spun in some past life and is a bit munged
up.

I ordered a new JT3 to MT2 arbor for it, but now I find I can't budge
the existing arbor out of the chuck. It's not rusty. I've soaked it
penetrating oil for about a day. I tried heating it with a torch and
then later by baking it in the oven. Quickly cooled the arbor with a wet
sponge while the chuck was still several hundred degrees from the oven.
I've succeded in slightly bending a Starrett center punch trying to
pound the arbor through the center hole in the chuck.

Any tips on things I could try to break up this long-term relationship?