Core Hole
The core hole is the pilot hole or pre-drilled hole for the internal thread: the diameter is smaller than the outer diameter of the subsequent thread.
Function in thread cutting:
- Determines the minor diameter of the internal thread.
- Must be drilled precisely so that the tap can engage correctly without being overstressed or damaged.
Practical example:
For a metric internal thread M6 (pitch 1), a core hole of approx. 5 mm is required – if the core hole is too small, cutting forces increase and the tool may break.