| 摘要 |
The disclosure is directed to an insert of hard metal material which when mechanically clamped to a recessed toolholder can serve as a cutting tool. The upper and lower faces of the insert have a substantially rhomboidal form and thus the insert is substantially in the form of a rhombohedron. The insert is provided with two single-point cutting edges which are disposed adjacent to opposite corners of the insert, each of which is in the form of an acute angle. By providing each of the cutting edges on a different opposite side of the insert as well as diagonally opposite one another, the insert when mounted in a toolholder can alternately present either of the cutting edges in an operative position. As a result the useful life of the insert between sharpening operations can be appreciably extended. As determined by the positioning of the recess in the toolholder, the insert can be mounted therein with a predetermined back rake angle extending from a substantially zero value to a positive back rake angle. Adjacent to each of the side cutting edges of the insert there is provided a groove which can serve as a chip breaker for a chip cut from a work surface. The surface of the groove extending toward and terminating in the side cutting edge can be provided with a positive side rake angle even though the face of the insert is disposed in the toolholder with a negative side rake angle. In this way both the back rake angle and the side rake angle can be established to be positive.
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