Used almost exclusively for the 5/16-32 White Lightnin touch hole liner. Never use high speed steel (HSS) taps for gunsmithing. High speed steel is perfect for a drill bit, but a poor choice for a gunsmith's tap. If broken, it is difficult to remove. Our high carbon steel taps are hard and sharp. If broken they are easily removed with a drift punch.
Plug taps have three to five threads chamfered, to cut threads in a through hole, or to start threads in a blind hole, closed at the bottom.
Tap Drills are smaller in diameter than the screw shaft to leave enough metal to cut threads.
Tap Drill: for 5/16-32 thread, use Letter Drill-I