Thought about using an extractor bit, but wasn’t sure about how much space would be needed/downforce since it’s hard to get two hands in the same space (though I can do it for short periods). Agreed. /u/Another4654556 is just using an improper tool, it’s too short and the base is way too fat. All screws have an appropriate size driver (1,2 or 3 mostly) Use the right tool, not just the first thing you find. They sell blocks and other devices online to immobilize the trem, though I’ve always just used the flat, rectangular pencil erasers of appropriate size. And more likely just the wrong size screw driver rather than too sharp. The handle with extra bits is causing issues with getting screw driver on screw close to straight. That mulitbit screwdriver is too offset, (angled too much) and is not getting a good bite on the screw. If you’re reaching max adjustment and you’re not getting the tension you need you can add more springs.
Take the springs off and get them out any way you can. I would just get the screw out any way possible and replace the handle. What I would try is use a rubber bend or piece of thin rubber over screw head and try using screwdriver that way to get it out. At that point the knob on the opposite side can probably just be pulled off too: you’ll be left with just the “base” attached on each side, and with the knobs out of the way you can get the screwdriver in directly instead of angled. While pushing the tab, pulling firmly on the “knob” on that side will pull it off of the “base”. One side of the knob will have a small metal tab, likely near the “neck” of the knob, that can be pushed in with a very small flathead driver. On a turning knob, only the two knobs and the rotating shaft are connected and the sit freely in the door so that they can turn. How can I remove a very tight screw (not stripped yet) from a door knob, while saving the door knob? This knob is very clearly a turning knob because of the locking mechanism in the photograph (the catch plate on the door frame should also have been a major clue).
Note that on stainless steel models like this, it is often the outside handle that needs to be removed first, so the hex screw-hole or push tab is on the outside knob (this way if someone were to remove the outside handle by force they would only remove the turning handle and the locking mechanism would remain in the door because the lock is integrated with the inside handle and not the outside handle). Imagine they’ll weld a new head on it and remove it that way. If that fails, the only solution I can think of is a new cylinder block, as there’s no way I’ll get the other bolts out behind the header joint (also corroded to shit). Get that under the screw and then turn the band round. There should be a tab or latch near the base of the handle that you can press with a flat screwdriver and then the handle will slide off of the post.
There might only be a small circular hole, and you will need to rotate the knob until you see the metal tab through it, then push the tab. It might use a tiny hex screw instead of a metal tab, but unlikely. For you drilling them out and rethreading the hole might be an option as they are probably big enough and probably have enough metal around them. You can buy bits that are for digging out screws with stripped heads. Go to Home Depot and buy some left-hand extractor drill bits. I had a similar issue with the smaller screws around the edge of the back plate on my 9550. I used the left handed drill bits from harbor freight. Drill it out, just be careful as that whole case is made of aluminum and fast moving steel bits will eat it up quick. Otherwise, I’ve had luck in the past using flathead bits and pressing really hard while unscrewing. Get a longer shaft or remove bits to place on screw with shallower angle.