Milling cutting insert

Details Milling cutting insert Milling cutting insert

1996-08-15

1998-03-17

Howell, Daniel W.

Cutters, for shaping

Rotary cutting tool

Including holder having seat for inserted tool

407113, B23C 502, B23C 520

Patent

active

057279110

DESCRIPTION:

BRIEF SUMMARY
FIELD OF THE INVENTION

This invention relates to an exchangeable hard metal cutting insert for use with a rotary milling cutter particularly, but not exclusively, for use in milling slots, shoulders or the like, with the side milled surface disposed substantially perpendicular to a milled base surface,
One or more of such inserts are releasably mounted in corresponding peripheral recesses formed in a rotary tool holder, each insert being provided with at least one cutting edge which, when mounted in the tool holder, is operatively disposed for milling operations.


BACKGROUND OF THE INVENTION

It is well known, with such rotary milling cutters, that it is advantageous to position each insert in the cutter so as to present a significantly large, positive axial rake angle.
With known rotary milling cutters such as, for example, that described in our prior U.S. Patent Specification Ser. No. 5,158,402, increasing the axial rake angle of the operative cutting edge on the insert involves providing a tool holder where the insert seat is sufficiently inclined with respect to the rotary axis of the tool holder that the cutting edge has the required positive axial rake angle. It will be readily understood that constructional considerations limit the degree of inclination of the support seat in the tool holder, seeing that an excessively high inclination would of necessity weaken the tool holder. Thus, with conventional rotary milling cutters, an upper limit was always imposed on the magnitude of the axial rake angle.
It was with a view to overcoming this restriction that it was proposed, for example in our prior U.S. Pat. Nos. 5,052,863 and 5,071,292, to provide the insert with a cutting edge which is inclined with respect to the base surface of the cutting insert. By so doing it is possible, On the one hand, to achieve an increased positive axial rake angle and, on the other hand, to maintain the insert support seat of the tool holder in a more or less conventional inclination, thereby not leading to the structural weakening of the tool holder. This solution, however, is limited by the size of the insert. Thus, the angle of inclination of the cutting edge vis-a-vis the base of the insert is a function of the ratio of the height of the insert to the length of the cutting edge. Thus, the longer the cutting edge, any increase in the angle of inclination or the cutting edge must be accompanied by a corresponding increase in the height of the insert.
It has furthermore been previously proposed, in our U.S. Pat. Nos. 5,158,402 and 5,232,319, to produce a cutting insert for use with a rotary milling cutting tool wherein the cutting edge includes a plurality of successive component cutting edges respectively merging via intermediate edges. These two prior U.S. patent specifications both disclose, with respect to FIGS. 9 thereof, a milling cutting insert having such component cutting edges, all of which present significant positive axial rake angles. However, as is clear from these figures and the associated description, each intermediate edge is directed from the trailing extremity of the immediately-preceding component cutting edge towards the base edge of the insert and, in this way, as can be seen, the insert is of progressively decreasing thickness (or height) as one proceeds from the leading to the trailing end thereof. It is therefore clear that, with such a construction, the magnitude of the positive axial rake angle which can be achieved is limited, seeing that any increase thereof would require a corresponding increase in the height of the insert. Furthermore, it is clear that the number of component cutting edges is limited, thereby limiting the length of the overall cutting edge of the insert. Thus, effectively, the prior proposal does not provide an effective solution to the problem of providing a milling cutting insert with a significantly higher axial rake angle whilst, at the same time, maintaining the same constructional requirements for the insert as a whole.
It is an object of the present invention to pr

REFERENCES:
patent: 5052863 (1991-10-01), Satran
patent: 5071292 (1991-12-01), Satran
patent: 5078550 (1992-01-01), Satran et al.
patent: 5150992 (1992-09-01), Friedmann
patent: 5158402 (1992-10-01), Satran et al.
patent: 5232319 (1993-08-01), Satran et al.
Patent Abstracts of Japan, vol. 9, No. 63 (M-365) (1786) Mar. 20, 1985 and JP,A,59 196 107 (Nihon Yakin) Nov. 7, 1984 (see abstract attached).

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