SNABBROTERANDE DORN FOR UPPTAGANDE AV ETT AV EN KRAGE OMGIVET HAL I EN METALLVEGG

摘要

A rapidly rotatable piercing tool of hard material for forming by frictional heat and pressure a hole surrounded by a boss in a metal plate or the wall of a metal pipe, the pipe part for making the hole to size having basically triangular cross sectional areas the contour line of which has three outwardly curved legs of a shape to make the piercing tool expecially adapted to forcing bossed holes both in ductile and in hard metals.