| 摘要 |
The bit for drilling stone for use in a hammer drill or an electric hammer comprises a body defining recesses which, in axial section, have a profile at least approximately in the form of an arc of a circle with a radius of between approximately 8 mm and 15 mm. The ratio of the surface area of guide lips each located between two of the recesses in the body of the bit and of the outer cylindrical surface defined by the bit is less than 5%, and preferably of the order of 1 to 2%. The diameter of a tip of the bit, which is provided with a plate of hard metal is equal to the diameter of said cylindrical surface in the vicinity of the plate. |
