I'm replacing the Bo-Mar rear sight on my 1911. The elevation screw was a bit funky so I want to chase the threads. I've found that it requires a 6/48 Taper Tap. While I can see the tap on Brownells websight, I have no idea what a Taper Tap is. How is it different from a regular tap, and what tips if any could you offer a novice like myself? (I am pretty handy with tools; gunsmithing is a bit different though)