Thread-drilling device has stepped surfaces of toothed webs in cut end inclined inversely to advance direction to reduce risk of breakage

摘要

The drill is designed so that in the cut end (2) the stepped surfaces (10) of the toothed webs (1) are inclined towards the drilling axis in inverse direction (12) to the advance direction (11). The inverse incline angle (14) is roughly equal to the angle of the thread pitch.