Thanks in advance.
Drill and replace.
You probably already did it, but I finally learned to tighten first and then loosen.
Kroil. It is a penetrant but superior to all others. Not cheap but it works where others don’t.
Torque them in the tightening direction momentarily then reverse torque with “impulse”. Repeat a few times as necessary.
Repeated thermal cycling. Impact extractors. Make sure not a lefthanded thread.
A blast from a propane torch or heat gun? The aluminum of the part should expand a bit faster than the steel of the screw, no? You might have to heat while exerting torque on the screws. If you don’t want top apply heat or think it might do damage, then get a block of scrap aluminum (or brass) and clamp it to your piece with no gap, you may be able to whack it with a medium hammer while applying torque to the screw but hitting the block, you won’t gall up the surface of your machine.
PB blaster or ATF and acetone.
soak and tap on them for a good while, leave over night.
Aluminium is soft and galls easily jaming them, worse than
stainless steel. When you put them in use a good anti-seize
and you won’t have this problem.
A dremel and a nut cracker is all you need. Cut the nuts close to the threads and then snap them off. Takes some time but easy peasy. You could drill them. You could try PB Blaster overnight soaked and I mean soaked wrapped in shop rags. Sounds like you have bimetal corrosion.
Nuke it from Orbit...it’s the only way to be sure.
Try a little heat. They could be secured by loctite, or seized, either way some heat could break them loose.
1) are the screws left-handed? (left to tighten)
2) if not, then “EZ-out’ kit the one you screwed up. On the ones you haven’t messed with, from autozone, there’s a catalyst product better than wd-40, called PB Blaster or Blaster Chemical Penetrating Oil.
Cut inch off the long end of allen wrench, put in screw and several firm blows with a hammer. Usually will make the difference.
Aerokroil.
Sounds like a flat head cap screw. Make sure you are using a quality allen wrench that is the correct size. Some cheaper made tools might not fit as well in the hex socket of the screw. Also, use a wrench with the shortest possible length—the farther the wrench sticks out of the socket, the greater the chance it will twist and break. When trying to turn the screw—push the wrench completely into the socket, and hold it there while applying torque—any misalignment can result in the wrench stripping out the screw.
If all else fails...get a left hand drill and drill out the screw. 23 years in a machine shop...pulled out a few stuck bolts and screws...
If you've already tried penetrating oil (not WD-40, real penetrating oil) you could try an impact screwdriver. If you ever worked on a motorcycle, you know all about them. The shock of impact combined with twisting action might break it loose.
Next I would try heat - just not too much. Aluminum and steel expand at different rates when heated. Try heating area around the screw with a propane torch, then applying ice or cold water to the screw itself.
All else fails, drill and easy-out. If you're careful and lucky you'll only have to replace the screws without having to fix the threaded holes .
Be sure to apply anti-sieze to new screws when reassembling, or they'll sieze up again.
Assuming you lost the hex hole... you can cut a groove with a hacksaw for a straight drive. Or grind flat edges on the screw heads for visegrip. If you lost the screw heads, you can drill and use an e-z out. I’ve had tough screws back out when reversing the drill (often because the screw head was gone and no longer forced against the surface.)
Good luck!
Heat and freeze, torch and can of freon or compressed air sprayed upside down. The use lube.
