Cold-form tapping of internal threads

An alternative to conventional tapping, cold-form tapping differs from conventional tapping in that it is a forming rather than a cutting process. The cold-form tapping is chipless since the thread is generated by a succession of deeper penetrating lobes on the tapered end of the tap. The thread is formed as the displaced material is pushed together axially between the lobes when the tap rotates into the hole. The results of comparative performance tests using various tap geometries, workpiece materials, and lubricants are presented.