| 摘要 |
<p>The drill bit (10) is for a drilling (40) with an out-of-round shape and with a cut-back section (46). The initial drilled section (42) is formed by an oscillating drill bit. To form a cut-back, the bit is rotated a least partially around its longitudinal axis to give a second drilled section (44) of a larger cross section than the first length. The bit has a shaft (12) with one end (14) clamped at the drill and a cutting head (13) at the other end (16). The cutting head has at least one radial projection (22,24,26) with a cutting edge, extending from the shaft.</p> |
