puur tsentriavade moodutamiseks enne puurimist või toorikute tsentrite vahele paigutamiseks treipingis või ümarlihvingis (vt tsentripuurimine), a drill in which a short parallel portion leads to a coned section with an included angle of 60o; used (1) to give accurate start to a twist drill, or (2) to provide a conical recess to ends of workpi