| 摘要 |
The present invention provides a unitized replaceable drill bit, and more particularly to a cutting tip of the drilling common bit, in which the central drill has an extended cutting edge, thereby to form a continuous cutting with the side cutting edges so as to prevent the cutting edge from chipping by built-up edge, and make the central drill become smoother and tougher, further to improve cutting property, easy manufacturing and efficiently reducing production cost, and improving competition capability in the market, wherein, integrating the central cutting drill and the level extended cutting edge into one whole body is to widen the cutting range, extend the cutting edge, and prevent chip from building up on the cutting edges and the cutting edges from breaking up; and building up a notch without cutting function on the joint portion of the bevel cutting edge of the central cutting drill and the level extended cutting edge separates said two cutting edges segments so that the cutting resistance may not be concentrated on the notch, and efficiently avoid the cutting edges being broken up; a couple of contact surfaces of the central cutting insert and the central cutting insert retain are built up a pair of dovetail fitting to improve the rigidity of the central cutting insert, further to improve cutting efficiency and performance.
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