custom tap

[TomG]

Chuck,

I've made a few special taps and they have always worked remarkably well. You should definitely not use a regular end mill to cut the flutes. The sharp corner created would almost certainly cause the tap to fracture. Just make a ball end mill to suit. All it takes is a radius gauge and a steady hand. The radius isn't even that critical, there just can't be a sharp corner in the flute. As far as the flute depth goes, Machinery's Handbook contains that information, or you can just copy another 1/4" tap. The depth is pretty standard regardless of the pitch.

Tom