Thread Relief
A thread relief is a short recess or groove before the thread start in a hole or pre-drilled hole, allowing the tap to engage freely.
Why it matters:
- Provides a clean start and prevents the tap from "pushing" or slipping sideways.
- Particularly relevant for deep holes or tight workpiece contours.
Practical example:
Before the actual thread cutting, a small relief groove is made in the metal so that the first cut of the tap engages correctly.