Use only U.S. made high speed steel taps. (Greenfield, TRW are good brands.) No if's or butts about this one. Use tapping fluid like stated above.

If you don't guide the tap, they are prone to breaking. Take a piece of steel that is flat and about 1" thick. Drill a hole in it the size of the tap's shank. Use a drill press, you can't do this by hand. It must be drilled at 90 degrees. Firmly hold or clamp this on to the part you are tapping. This supports the tap and keeps it at 90 degrees to the part. (I have a tapping block that I made of tool steel that is 2-1/2" X 2-1/2" X 1-1/4" thick, with all of the tap sizes #2 thru 5/16".) Use a quality tap handle (Starrett or General). Take it a little bit at a time. When the tap gets dull, get a new one. Keep the old taps to clean out old threaded holes or make 'bottoming' taps out of them by grinding off the tapered tip. Taps and drills are cheap compared to the parts you are working on.

Remember: Cheap tools-poor results. Best place to buy-www.use-enco.com. (Enco is a cheap division of MSC tools.) They have cheap junk, too, so buy carefully.

From Lightning at the AK-47 forum.