Tapping
| Reusability | Non-Reversible |
|---|---|
| Materials: | Lubricants, Metals, Plastics |
| Tools: | Taps, Dies, Tap handles |
Introduction
A common method of threading is cutting with taps and dies.
Challenges
Unlike drill bits, hand taps do not automatically remove the chips they create. A hand tap cannot cut its threads in a single rotation because it creates long chips which quickly jam the tap (an effect known as "crowding"), possibly breaking it.
Approaches
Therefore, in manual thread cutting, normal wrench usage is to cut the threads 1/2 to 2/3 of a turn (180 to 240 degree rotation), then reverse the tap for about 1/6 of a turn (60 degrees) until the chips are broken by the back edges of the cutters. It may be necessary to periodically remove the tap from the hole to clear the chips, especially when a blind hole is threaded.
For continuous tapping operations (i.e., power tapping) specialized spiral point or "gun" taps are used to eject the chips and prevent crowding.
