| 摘要 |
A drill bit has inserts (14) of hard metal as cutting and abrading elements. The bit body is formed as a hollow cylinder (10) closed at one end and adapted to be screwed to a shank (11), the closed end is pierced by forwardly tapering apertures, and complementally tapered inserts (14) are positioned in the apertures and the shank is provided with a replaceable backing plate (18) of hard metal, to abut the rear ends of the inserts. |
