There are also different kinds of pipe taps. they have straight pipe taps and tapered pipe taps. You usually find the tapered pipe taps. Those are sensitive to how deep you run the tap as it is tapered. If you run it too deep, your part will run all the way through the part before reaching torque, then the hole is too big. With a tapered pipe tap, you have to go a few threads at a time and then check with the part. then maybe two or three threads more and recheck with the part again. Repeat as necessary.
If you can find a straight pipe tap, that is the better way to go. It doesn't open up the diameter of the hole where the mating part will not fit, like the tapered pipe taps can do.
