Cutting insert

Details Cutting insert Cutting insert

1995-05-11

1998-06-02

Rachuba, M.

Cutters, for shaping

With chip breaker, guide or deflector

Comprising concave surface in cutting face of tool

407113, 407115, B23B 2722

Patent

active

057589941

DESCRIPTION:

BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS

This application is the U.S. national phase of PCT application PCT/DE93/01108 filed 18 Nov. 1993 with a claim to the priority of German application P 42 39 236.5 itself filed 21 Nov. 1992.


FIELD OF THE INVENTION

The invention relates to a polygonal cutting insert with on the cutting surface raised chip-forming elements that are arranged in a row next to one another at a spacing from the cutting edge and which are each elongated with a respective longitudinal axis which forms an acute angle with a perpendicular to the cutting edge.


BACKGROUND OF THE INVENTION

Such a cutting insert is known from U.S. Pat. No. 4,969,779.
A cutting tool is known from German 2,231,631 having a chip-breaking groove in which at least one frustoconical projection is provided in a cutting corner.
It has also already been suggested to arrange a plurality of part-spherical chip-forming elements next to one another in a chip-breaking groove.
The known cutting inserts are nonetheless, due to the arrangement of the chip-forming elements and the geometry of the chip groove, only usable in a limited range of different cutting conditions, as with various cut depths and feed rates. In order to improve the usability of the cutting inserts and to better shape and remove the chip German 3,148,535 suggests forming the chip-forming elements generally frustoconically with generally triangular base surfaces, each having a base line aligned parallel with the adjacent cutting edge or on an arcuate line.
According to German 2,819,824 a cutting insert is suggested having in its center a boss (plateau) which is formed as a polygon and whose basic shape corresponds to that of the cutting insert. In particular the corner of the rectangularly shaped boss is aligned to the center of the cutter but is otherwise formed annularly. Such cutting inserts are also known where the chip-forming boss extends right up to the cutting corner region. The disadvantage of such embodiments is that during cutting high pressure is produced which can lead to premature wear of the cutting insert. In addition the achieved cut quality is unsatisfactory.
In order to ensure uniformly good chip formation at widely different feed rates, cut depths, and cutting speeds it has been suggested in European 0,278,083 to provide a cutting angle of more than 30.degree. on the land adjacent the cutting edge, the cutting angle decreasing away from the land, and chip ribs projecting outside the cutting surface are provided in the cutting surface region extending in the chip-travel direction and between the cutting-corner regions of the cutting insert, between which chip ribs further bumps with run-on ramps are provided. The corner region has three adjacent spur bosses of which the two outer ones have their chip longitudinal axes parallel to the adjacent chip ribs.
Run-on ramps are also provided in the (plunge) cutting insert according to U.S. Pat. No. 4,992,008, these ramps being directly at the cutting corners and extending as a wide roof surface in the direction away from the cutting edge of an elongated chip-forming element with a trapezoidal shape.
The cutting inserts described in European 0,168,555 and 0,222,317 have a central plateau that is raised relative to the cutting corners and cutting edges and from which part-spherical projections extend toward the cutting edge and extend if necessary into a chip-forming groove provided there.
European 0,414,241 describes cutting inserts with pits which interrupt the cutting edge and thus form groove-like cutting-edge formations. This arrangement nonetheless has a wearprone cutting edge that is likely to chip.
Part spherical chip-forming elements do indeed lead during chip formation to a desired chip formation but the chip is neither laterally sufficiently guided in the chip-travel direction so that lateral breaking of the chip can lead to over deformation of the chip and no actual chip breaking or insufficient chip breaking. Longitudinally elongated chip-forming element guide the chips better in the

REFERENCES:
patent: 4215957 (1980-08-01), Holma et al.
patent: 4632608 (1986-12-01), Blomberg et al.
patent: 4969779 (1990-11-01), Barten
patent: 4988242 (1991-01-01), Pettersson et al.
patent: 5074720 (1991-12-01), Logvist et al.

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