Removing stubborn screw

[TomMull]

Probably too late now, but my suggestion would be a hand impact tool, like

It seems like the stout hammer blow directed inward seems to help loosen the screw, as well as help keep the bit from camming out.

If the slot is too badly damaged, you can try cutting a new one with the Dremel and an abrasive cut-off blade. If that doesn't work, cut a few more slots and collapse the head until you can get the ring off, then cut a new slot deeper and try again with the impact tool.

Yes, good tool. However, the one I got from Craftsman (Sears) recently had a very brittle flat bit which broke on the first whack. No warranty on the bits, I'm told. Hard to find on wide enough with the correct hex size too. If you can get some good bits, the end will go right on your 1/2 " air impact and this works really well for me.
Tom

 

[TR3driver]

No warranty on the bits, I'm told.

I'd ask for the manager. The web site clearly states "Satisfaction guaranteed or your money back." Mine is a cheap no-name that I've had for probably 30 years and I've never broken one of the original bits. Come to think of it, though, ISTR the shank on my bits is 3/8" while the photo above (from Sears) looks more like 1/4".

Anyway, I've made more bits by grinding down a 3/8" hex key (from the local surplus house) and they seem to work well. I needed an extended, large flat blade to loosen the door hinge screws on the TR3; not enough room to use the supplied bit in there.

 

[aeronca65t]

......Anyway, I've made more bits by grinding down a 3/8" hex key (from the local surplus house) and they seem to work well........

That's a great idea!