I get most of my non specialty tools from the hardware store,but some days,a trip to Ace just isn't going to happen and you need something done NOW. Here is a screw extractor I made when I didn't have the right size for the job. It's a bit shoddy and it's really a one use only tool, but it got the job done. I keep a bag of scrap metal tubing (available from the hobby shop) of various sizes and lengths. I selected a piece of brass tubing that had an inside diameter big enough to fit around the screw I was extracting. Using my belt sander as a grinder I put a nice bevel on the edge. I sharpened it up using a small diamond whetstone. Using a hobby saw, I cut some teeth into our "blade". You should be able to fit at least three of these teeth on there.
So,for what purpose do I need such a questionable looking tool? Stay tuned for tomorrows exciting episode of Guitar Omnivore!