Greenlee DTAP8-32 DRILL/TAP, 8-32.

These are awesome but i would recommend following Greenlee's drill chart. I have used the 8-32 in particular to tap a lot of 1/4" copper bussing and would not recommend going full bore with a drill unless you have a already pre drilled a hole that is fairly big but where the tap will still cut threads. I would also recommend using some type of lubrication to avoid seizing up in thicker material. If you have found you pre drilled too small of a hole like i have many times, apply plenty of lube and alternate between tightening and loosening until you can either back it out or completely tap the hole. If you are not skilled enough to use these with a drill I would definitely recommend using them with a multi bit screwdriver.