So I got a good deal on a used, but decent 1970's atlas 3950 6x18 metal lathe... I am in the process of stripping all of the parts (which were coated mostly in oil, and only a small bit of surface rust--not on the ways thankfully...)... There are some set screws on the topslide that are really stuck--found this out the hard way when I took half the head off of one (theyre flathead--go figure.) being overzealous and excited. The screws are probably an eight of an inch in diameter, and I dont have an extractor that small, though Im sure I could find one on the net. I am currently applying kroil to them every so often, and will begin soaking the whole thing in kerosene in the next day or so. Obviously I cant apply heat to this thing being part of a precision machine, does anyone have any bright ideas or experience? Also, there is a jacobs chuck firmly wedged in the quill of the tailstock. I got the quill out of the tailstock no problemo, but the chuck... thoughts on that? Pics when I get some of this shit cleaned up

If all else fails, try this:
Find a drill bit slightly smaller than the hole that the set screw is lodged in. Drill out the set screw with that bit, it'll do two things: If you keep a steady hand it won't dick up the threads, and it should remove enough of the stuck set screw to get the two pieces apart. Figure out how deep you need to drill and put a stop (or at least some tape) about that far up on the drill bit so you can avoid drilling straight through and into the next piece. Once you have it apart, chase the set screw's leftovers out of the threads with an appropriately sized tap. Put in the new set screw and use some anti-seize compound on the threads.
Good luck!

Posted by Brent If all else fails, try this: Find a drill bit slightly smaller than the hole that the set screw is lodged in. Drill out the set screw with that bit, it'll do two things: If you keep a steady hand it won't dick up the threads, and it should remove enough of the stuck set screw to get the two pieces apart. Figure out how deep you need to drill and put a stop (or at least some tape) about that far up on the drill bit so you can avoid drilling straight through and into the next piece. Once you have it apart, chase the set screw's leftovers out of the threads with an appropriately sized tap. Put in the new set screw and use some anti-seize compound on the threads. Good luck!

Yeah, thats kinda what I was coming to on my own--I think Ill hold the top-slide in a milling vice and put the bit in a collet to keep it steady, center punch it and pray. thanks man

Also, if you have a really good tool store, perhaps you can find a left hand drill bit. Then, when you get partway through, it may just back out while you are drilling it. I've done this before when drilling a hole to put my extractor in to back out a busted screw/bolt/whatever. The first time it really surprised the heck out of me when the bit caught on the screw and the whole thing backed right out.

Posted by MrMusik Also, if you have a really good tool store, perhaps you can find a left hand drill bit. Then, when you get partway through, it may just back out while you are drilling it. I've done this before when drilling a hole to put my extractor in to back out a busted screw/bolt/whatever. The first time it really surprised the heck out of me when the bit caught on the screw and the whole thing backed right out.

I got it out-- I soaked the whole thing in a 50-50 mix of acetone and automatic transmission fluid for a few days, came back to it and gingerly grabbed the remaining head with a fine pliers, she came right out--clausing is sending me the replacement screw for a buck--Im thrilled. Some parts that are cleaned and good to go: