Polygonal cotting insert

Details Polygonal cotting insert Polygonal cotting insert

1998-01-15

1999-09-14

Pitts, Andrea L.

Cutters, for shaping

Including tool having plural alternatively usable cutting edges

407114, B23B 2702

Patent

active

059512156

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

The invention relates to a polygonal cutting insert with a cutting faces a support face, and a plurality of side faces that together with the cutting face form cutting edges and rounded or chamfered cutting corners below which the adjacent side-face regions border one another over a shape corresponding to the cutting-corner shape.


BACKGROUND OF THE INVENTION

European 0,160,278 describes and illustrates such a cutting inserts This cutting insert has below the cutting edge and spaced therefrom a side-face region reaching to the support face that is set back relative to the overlying side-surface region that goes to the cutting edge.
In addition cutting inserts, in particular rhombic cutting inserts with acute-angle corners, are known which have on the side face at a spacing from the cutting edge below the corner region a set-back side face produced by machining. The transition regions between two adjacent side-face sections run together at an ever acuter angle toward the support face or have seen in section a constant corner radius of the transition regions between two side faces.
The disadvantage of the above-described cutting inserts is that they either have very small corner radiuses below a cutting-insert support face at a cutting corner, so that there is the danger of breakage, -or with set-back side-face transition regions the support face is made very small which reduces the stability of an indexable cutting place installed in a tool holder. As the side-face regions are worn off increased costs and labor are encountered Corner regions with small radiuses in the region of the support face are very hard to manufacture by pressing.


OBJECT OF THE INVENTION

It is therefore an object of the present invention so to improve the above-described cutting insert that it has greater edge stability in the region of the side-face edges in particular in the transition region of two adjacent side faces near the support face.


SUMMARY OF THE INVENTION

This object is achieved by the polygonal cutting insert according to claim 1 which is characterized in that a corner surface or transition region between two adjacent side faces has in a region adjacent the support face a maximum width at least relative to the width of overlying regions. With this simple expedient that can be produced relatively easily by press technology through appropriate formation of a mold one gets a more stable mounting of the cutting plate in the transition region of two side faces that does not deleteriously affect the formation of the geometry of the cutting edge and the cutting corners As a result of the features of the invention, fracture failure of the cutting insert in the side face region bordering on the support face is avoided.
Thus according to a first embodiment of the invention the width of the transition region (of two adjacent side faces) increases continuously from the cutting face to the support face. According to an alternative embodiment the width of the transition region is at first constant from the cutting face to the support face and then increases uniformly and/or step-wise. This embodiment includes such embodiments wherein the width of the transition region only increases over a certain distance continuously to the support face while there is always the requirement that the width of the transition region in the region is maximum in the region of the adjacent support face.
In a further embodiment of the cutting insert according to the invention the width of the transition region increases below a spacing of at least 20% of the cutting-insert height.
Preferably the maximum width is 1.1 to 3 times preferably 1.1 to 1.8 times, as large as the minimum width of the transition region. This minimal width can either be defined at the region adjacent the cutting edges namely when the transition region there to the support face widens or at a spacing from the cutting edge such hat the width of the transition region toward the support face at first decreases or remains constant and then again increases to

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