Other trick is to lube it with penetrating stuff for rusted bolts/screws.Now, you use a metal chiesel (small) and a hammer, and bang the screw in a counterclockwise way, on it's edges..
Wait, ill do a schematic..
Try to use a well sharpened, small size chiesel to start, make some good marks and use a bigger one hitting harder. Remember, the more metal you chop off, the less chances you got left.
This is how i got many stuck brake screws loose at home. I dont have torches, this seemed the easiest way!
If you got new ones you want to put back on; use plenty of anti-sieze compound, and DO NOT tighten them. Just sit them enough so they wont unscrew themselves..
