Chamfer Length
The chamfer length of a tap refers to the number of chamfered thread turns at the front, tapered part of the tool. This area is responsible for the main engagement with the material and the guidance of the tap.
- Short chamfer (e.g. 2–3 thread turns): Allows threading closer to the bottom of blind holes, but results in higher cutting force per tooth and a more aggressive cut.
- Long chamfer (e.g. 6–8 thread turns): Provides a gentler cut, distributes the cutting load across more teeth and thereby increases tool life. Requires more clearance in blind holes before the full thread profile is reached.
Practical example:
In deep blind holes, a stepped approach is often used with taps of different chamfer lengths, starting with a longer chamfer for the roughing tap and ending with a shorter chamfer (bottoming tap) for maximum thread depth.