I think I left it in there too long and it has seized. I've tried Kroil and heat, but it won't budge. The outer collar is loose, and spins free for one full turn, but I honestly don't remember if is is supposed to come all way off, or if is just loosens enough to remove the collet and endmill. (I am a beginner hobbiest and I've only used this thing sparingly...)

I do remember that something internal to the holder was asymetric. I think it was the part that the groove in the collet snapped into, like I had to insert it at an angle. I just can't remember if I need to apply side force to get this thing back apart.

Is there something simple I am missing? I can apply more force if needed, but wanted to check first in case there is a better way. (I've already chipped the flute up high putting a vice grip on it)

Maybe I could get the taper off and drive the endmill out from the inside? Again, not sure if this thing comes apart like a couple of my chucks do.

I don't mind sacrificing the cutter as long as I can salvage the holder and maybe the collet too.

Any ideas?

R8 collet on your mill? If so, just whack the tightening screw/rod and the mill should come out. Yes, the collets come out. Heat was probably a bad idea here. Collets need stay springy otherwise your mills will stick; although we might be past that stage now.

Turn the collet ring one more full turn and it will pull the collet out with the ring

The heat was just a short fanning with a propane torch to get it a little past the point of being able touch it. Just because it was cold in the garage. I'm not worried at all about affecting temper, I was careful not to overheat.

Should the collet ring spin all the way off then? I thought it should, maybe I just need to try harder...

Turn the ring till it pops the collet out of the tapper

I usually just loosen the bolt and then tap the top of it with a big hammer, have a rag or something the catch the end mill when it falls out the collet. If it's tighter than that loosen in a couple of turns set a wooden block on the table and using the quill feed bump the mill into the block until it comes loose. If it's worse than that take the collet and mill out together and work on in then. It's not an uncommon occurence.

I got it out, thanks guys. Problem was the holder and cutting mill were already off the machine so I was limited in the torque I could apply. Put it back in the machine, locked it, wrenched the retaining collar a little harder an the bit dropped right out.