| 摘要 |
A rotatable holder fixes the pin of the drill crown in a grinding position in which the pin has its longitudinal axis aligned with the rotary axis of the holder. The pin rotates around its own longitudinal axis and a driven spindle is provided for the grinding tool. The grinding wheel (8) with its casing (7) is pressed against a projection (16) on the spindle (4) in a position in which its interior is at right-angles from a point (17) where the rotary axes (3,5) of the holder and spindle intersect one another. |
