I had to do exactly that. I have 4 large non-opening ports
frames inside and out joined by SS screws.
- I could not heat it because the lenses (acrylic) were too close to the frame.
- I could not use impact driver as it would damage the frame.
- I could not use penetrating oil because it was horizontal and the screw head tight against the frame (not countersunk).
It all depends on what kind of screw head
you have. If itís a philips, be very careful because if you mess up the head youíll have to drill to extract. If it is a square (Robertson?) you are lucky as it takes a lot of torque. If it is a slot (mine were) then you are better than a Philips but worse that a square. I messed up some slots but I was able to recreate them with a hack saw.
I got the biggest with the thickest handle screw driver that fit the screw slot snugly (no side to side play). A big one will provide a better grip as you'll need to use both hands.
I leaned against the screwdriver and very slowly tried to tighten
the screw and 10 times out of 10 it moved a hair, and that is all you need. Now turn it the other way (untighten) a little. Next tighten some more, and so on. Keep going back and forth until you have a good momentum to really untighten it by a quarter turn. Be patient, don't put too much load or you'll break the head. Once the head is off the frame you are almost home free but donít celebrate as you may have another 50 to do.
I was able to remove all of them (20 from each port). I was lucky as I had no plan B due to the above. But I really like Roverhiís idea of the electric arc
as it provides quick localized heat.