Free core hole diameter calculator

Calculates the recommended core hole diameter for cut and formed metric threads.

Nominal diameter

Pitch

Method

Formulas

cutting tap: D ≈ d − P; forming tap: D ≈ d − 0,5 · P

Sources: ISO 68-1: metric basic profile; ISO 724: basic dimensions of metric threads.; https://guhring.com/media/tools/815.pdf