| 摘要 |
An undercutting drilling pin is composed of a threaded bolt (20) having at its front end (21) a conical expansion and can be set into a previously drilled hole (11) with its front end first, and of a drilling sleeve (30) that can be slipped on the threaded bolt and moved with respect thereto in such a way that an axially slit end portion of the drilling sleeve can be stretched out by the conical expansion. The outer surface (35a) of the drilling sleeve (30) in its slitted end portion and the axial terminal surface (35b) are at least partially coated with hard particles, so that when the drilling sleeve is stretched out and turned at the bottom of the drilled hole a conical undercut can be formed. The coating (36) of hard particles is about 0,3 mm thick and is preferably composed of particles of hard chrome or of tungsten carbide applied by flame-spraying.
|
