| 摘要 |
The invention relates to a coupling between a drill bit (7) and a drill shaft (6), which at least in an end position in one rotation direction gives an interlocking free from play between the elements, whereby simultaneously the drill bit (7) can be freely rotated in relation to the drill shaft (6) in opposite rotation direction. The drill bit (7) is at the inside provided with a helical spline (11) in which a parallel helical spline (10) arranged on the drill shaft (6) is engaged. The axial motion of the drill bit (7) is delimited by aid of a joint consisting of a peripheric notch (9) cut into the drill shaft (6) and a pin (8) firmly connected to the drill bit (7). The splines (10, 11) have the same pitch s, which is greater than the sum of the spline widths b'+b'', and this brings about that the drill bit (7) can be freely rotated on the drill shaft (6) between two end positions. |
