| 摘要 |
The present invention relates to a rock drill bit (1) for percussive drilling. The drill bit comprises a bit body (2), a head portion (3) defining a longitudinal center axis (CL). The head portion (3) includes an axially forward rock-crushing surface (8) and a skirt (5) that extends axially rearwardly from the rock-crushing surface (8). The rock-crushing surface comprises several rock-crushing means (4,6). A circumferential outer surface of the skirt is provided with circumferentially spaced apart grooves (11) forming lands (15) therebetween. The grooves and the lands extend generally in an axial direction. An axially rearward portion of a land (15) is provided with a guiding surface (19,20). The guiding surface (19,20) faces radially outwardly. The guiding surface comprises at least one step (22) or a sloping surface such to reduce the diametrical dimension stepwise or continuously, respectively. The guiding surface comprises a first guiding portion (19) and a second guiding portion (20) both situated radially outside of an imaginary extension line (21) of the waist (15A). The first guiding portion (19) projects farther radially outwardly than the second guiding portion (20) relative to the center axis (CL) of the drill bit.
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