Due to the processing principle of forming taps, a "slit" (crack-like fold) always forms at the crest of the thread.

If this shape is defective, the following causes are likely:

Insufficient crest formation: The pilot hole diameter is too large, resulting in insufficient material flow to fully form the thread crest.

Over-rolling: The pilot hole diameter is too small, causing excessive material displacement (over-filling) and distorting the shape.

Recommended Products:
V-EG-NRT: This type trims the thread crest during the dolling process to ensure stable major diameter and shape.
IT-NRT: Designed for small-diameter precision parts, this type suppresses the slit at the crest during rolling to create a smoother finish.