| 摘要 |
A masonry drill bit includes a cutting insert (3) which is substantially roof- shaped in sideview and has on each side of its "roof" one lip (6). Each lip (6) includes a leading cutting surface (7) and a trailing free surface (8), wherein the mutually abutting free surfaces (8) at the roof ridge (9) define a chisel edge (10). Each free surface (8) is concave in a sub-zone (8a) adjacent to the chisel edge (10) in a manner that the radially outer ends (11 ) of the chisel edge (10) axially protrude at the end face (12) of the insert (3) relative to the in-between center of the chisel edge (10). Each lip (6) includes at least one recess (13) and to that extent deviates from the substantially roof-shaped geometry. |
