Cutters – for shaping – Including tool having plural alternatively usable cutting edges – With integral chip breaker – guide or deflector
Patent
1997-05-15
1999-03-02
Pitts, Andrea L.
Cutters, for shaping
Including tool having plural alternatively usable cutting edges
With integral chip breaker, guide or deflector
407115, 407116, 407113, B23B 2722
Patent
active
058761543
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a cutting insert for chip forming machining of metallic work pieces, having at least one cutting edge limited by a rake face and a clearance face, the rake face being provided with a rake face section adjoining the cutting edge which has a positive rake angle relative to the cutting insert plane, and with a plurality of dome-shaped recesses which are arranged parallel to the cutting edge at a distance from each other, moulded into the rake face section, limited by their upper edge with respect to the rake face section and partially penetrating the cutting edge.
BACKGROUND OF THE INVENTION
It is known that chip breaking and chip removal during cutting can be facilitated by the provision of recesses in the rake face (DE-C-28 40 610). The chip obtains there during the cutting operation a wave-like structure and thereby a greater stiffness which is necessary for easy breaking. Especially for drilling, small, short broken chips are important for undisturbed stress relief. For this purpose suitable deformation of the stiffened chip, which leads to reliable chip breaking, is additionally required.
Starting with this, the present invention has the object to improve the known cutting insert of the kind. described above in such a way that during machining the formation of small, short broken chips is facilitated.
SUMMARY OF THE INVENTION
In order to attain this object, a cutting insert is provided having at least one cutting edge limited by a rake face and a clearance face, wherein the rake face has a rake face section adjoining the cutting edge which has a positive rake angle relative to the cutting insert plane and a plurality of dome-shaped recesses which are arranged parallel to the cutting edge at a distance from each other, moulded into the rake face section, limited by their upper edge with respect to the rake face section and partially penetrating the cutting edge, wherein there is provided a chip forming step on the side of the recesses opposite the cutting edge which projects beyond the rake face section, which step is limited by a lower limiting line on the side of the cutting edge and an upper limiting line away from the cutting edge, and wherein the rake face in the region of the dome-shaped recesses has a neutral or negative rake angle with respect to the cutting insert plane, characterized in that the recesses are formed as conical, cylindrical, ellipsoid or parabolic domes penetrating the cutting edge with their lowest surface line being substantially perpendicular to the clearance face.
The present invention is mainly based on the consideration to subject the chip, which was provided with a wave structure during machining, to a suitable deformation in a most confined space, by which it is broken into small pieces. In order to achieve this, the present invention provides for a chip forming step on the side of the dome-shaped recesses which is opposite the cutting edge, which step projects beyond the rake face section containing the recesses in the direction of chip breaking, and for the rake face being provided in the region of the rake face section with a positive rake angle and in the region of the recesses with a neutral or negative rake angle with respect to the cutting insert plane. An especially advantageous cutting and chip breaking behaviour is achieved when the rake angle of the concave rake face section is 15.degree. to 25.degree., while in the region of the recesses, at the cutting edge, it is 0.degree. to -10.degree..
During machining, the chip, which was provided with a transverse wave structure, is pushed in the chip travel direction against the chip forming step and is sharply deflected . The deflection leads to chip breaking, so that small, short broken chips are created. The chip breaking step can run at its limiting line at the side of the cutting edge tangentially into the rake face section, while, at the side of the limiting line away from the cutting edge, it can change sharp-edged into a central rake face plateau whi
REFERENCES:
patent: 4988242 (1991-01-01), Pattersson et al.
patent: 5044840 (1991-09-01), Fouquer et al.
patent: 5709509 (1998-01-01), Wegener et al.
patent: 5743681 (1998-04-01), Wiman et al.
Komet Praezisionswerkzeuge Robert Bruening GmbH
Pitts Andrea L.
Tsai Henry W.H.
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