The left-hand tap intermediate tap (No. 2) allows you to shape a left-hand thread before finishing it with the finishing tap (No. 3). The advantage of pre-cutting a thread with the intermediate tap (No. 2) is that the cutting forces on the subsequent finishing tap (No. 3) are reduced. The intermediate tap (No. 2) is marked with two rings and removes approx. 85 percent of the thread profile. Because no complete thread profile is cut, the thread is not yet usable. Only when the finishing tap (No. 3) completes the thread in the last process is it fully usable. By dividing the work between two or three taps, it is easier to cut a straight and clean thread by hand.
Compared to the machine tap, the hand tap has a short shank. This allows you to cut internal thread by hand without jamming and can be operated with tap wrenches, tool ratchets or other holding tools with square drive.
The thread can be cut in a pre-drilled core hole.
A left-hand thread is tapped counterclockwise. The left-hand tap or left-hand screw tap is also operated counterclockwise.