I have an old (English-made) Record Nº5 4" vise that works well but the jaws are badly worn. I ordered replacement jaws on Amazon, but the problem is getting the old jaws off. They are secured with slot-head screws but I can't get the screws out.

I've tried applying Kroil overnight, heating with a propane torch and letting cool, tapping with a punch to loosen, and lastly, an impact screwdriver which I ground a tip to the right thickmess, so I'm pretty much out of options and thinking that my last recourse may be to (carefully) drill them out with a slightly smaller bit, maybe just down to the threads in the body at first so I can knock the jaws loose.

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