| 摘要 |
<p>A hole-forming tool having an elongated body which is provided with two opposite ends and a bore extending into it from one end. The end of the body is tapered inwardly to a leading end of the body. The end is further provided with an non-uniform taper of: (a) between 12 DEG to 18 DEG to the longitudinal axis of the body at the leading end; and (b) from 4 DEG to 8 DEG to the longitudinal axis of the body at a portion remote from the leading end. <IMAGE></p> |
