Wish it was this simple on older style PKs , had to do a set a few years back that some moron
had attacked the Phillips heads with a bit that was too small and totally distroyed the heads so that we had to use the removal bits Steve posted,where you drill it out to a tapered
cone and then remove with the special tip that fits it with same taper. However the threads were so
bad that when you hit them it would either cut the head right off the shafts, or tear the nutplates off or
twist them all up! Ended up actually replacing 82 of the nutplates, so turned into a pretty big job to
straighten them out compared to Edo's. Those covers had not been off for dozens of years. Of course
inside we found hoses that had come loose from the retaining brackets and then curled up on the ends
so that when you pumped the compartment, and you heard it pumped dry, you assumed it was. Of course
it was leaving 3/5" of water in the bottom of that compartment. Even in a small set of floats like 1800's.
A little math showed that you could easily have 50lbs of water in a bigger compartment when those hoses are not right down
hard into the bottoms, where they are soposed to be. We replaced all the screws with new SS ones , and silver never-seize, any nutplates that were not replaced we ran a tap thru so there was no galling on the threads of the new screws. Anyway; the whole mess was a couple of days work that could have easily all been avoided
if the screws ,had simply been at least ALL pulled once a year, and a few drops of oil put on the threads and reinserted,compared to letting them set for years in that highly corrosive environment ,and then trying to take them out with a drill,with the wrong bit in it! Of course now you can pull a cover in 30 secs, to see what's going on in there. However
it turns out to get there was quite an envolved project that no one wanted to take on. Pita project.
The brace and bit is of course how most high quality guns are assembled so that when you try to disassemble them with a hand screw driver you will usually not be able to turn the screw and end up tearing the heads up trying! When we make new breach pins we always time them to come out at 11 o' clock then " stretch em" in to 12 o' clock, with a brace and bit, that you hollow grind the bit to fit exactly the slot in the head of the screws. There is plenty of torque there!
On breaking threads free that are corroded, there is a product from Chemsearch
called "Yield" that is about the best I have ever used. However it is hard to find and
pricey! We use it on gun barrel threads, that have been on for a hundred years (old Winchester n Marlins)and it will show up 10/12 threads later,inside the frame 10x faster than Kroil or PB........
CRC "Freeze-Off Super Penetrant" is another good bet.