| 摘要 |
The end of the bit (3) opposite its tip (4) fits in a portable rotary hammer-drill, and it passes through the axial bore in the enclosing fixing component (2). The external diameter of the component is greater than that of the circle described by the tip (4). The bit and the component do not rotate together during the fixing operation. The axial hammer-blows are transmitted to the component, which is driven into the drilling at the same time as this is being formed. Cutting edge (8) can be provided at the component forward end, which is of different cross-section from that at its rear end. |
