| 摘要 |
The drill bit comprises two cutting tips (4, 5) fastened removably in housings made at its end, the sharp cutting edges of these tips opening out into helical grooves (2, 3) made within the body (1) of the drill bit and each of these edges providing, as the work piece or the drill bit revolves, part of the total cutting surface of the said drill bit. One of these two tips has a cutting edge of circular shape (4) arranged radially and comprising two points of intersection with the longitudinal axis of the drill bit. The other tip has a cutting edge of rhombic shape (5) and is located in a plane parallel to the plane containing the circular cutting edge. <IMAGE>
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