Cutting tool and cutting insert

Details Cutting tool and cutting insert Cutting tool and cutting insert

1999-02-08

2001-07-03

Wellington, A. L. (Department: 3722)

Cutters, for shaping

Including tool having plural alternatively usable cutting edges

C407S114000, C407S116000, C407S040000, C407S047000

Reexamination Certificate

active

06254316

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates to a wiper insert and a milling cutter.
BACKGROUND OF THE INVENTION
In tools for metal cutting having indexable cutting inserts of hard and wear resistant material the cutting edges are subjected to wear and sometimes some part of or the entire cutting edge collapses. If a small insert fractures, only the cutting edge collapses without any risk for damage to the tool body. If a large insert fractures, the risk of damage to the tool body increases to an essential degree. If the cutting insert is not seated on a shim then a fracture of the insert often gives rise to damage of the tool body. To avoid such damage it is usual that the cutting insert rests on a shim of cemented carbide. A usual combination is a cutting insert having a thickness of about 5 mm and a shim having a thickness of 3-5 mm. This results in a total thickness of the cutting insert and the shim of 8-10 mm.
Rivière U.S. Pat. No. 5,147,158 shows a four-sided cutting insert having an integrated shim so as to provide a fracture zone. The cutting insert comprises an upper rake face, a lower face, and an edge clearance face interconnecting said upper and lower faces. The edge clearance face includes a step located intermediate the upper and lower faces. When the insert is in use the step defines a zone with a strain peak such that in the event of insert breakage, the propagation of the crack will be guided to the area of the step. The portion of the insert located below the step remains intact and thus protects the tool body.
Tsujimura et al. U.S. Pat. No. 4,966,500 shows a milling cutter having octagonal or hexagonal cutting inserts. Each cutting insert has a segmented (non-linear) major cutting edge, an end cutting edge and a radially inner cutting edge. The radially inner cutting edge is supposed to cut during coring of the work piece. The known insert lacks fracture zones so as to prevent an insert breakage from transferring into the seat or shim. Furthermore the known milling cutter cannot produce very fine surface finish.
OBJECTS OF THE INVENTION
One object of the present invention is to present a wiper insert and a milling tool that overcome the disadvantages discussed above.
Another object of the present invention is to provide a wiper insert and a milling tool providing a very fine surface finish.
Still another object of the present invention is to provide an economically favorable wiper insert providing at least three wiper edges.
Still another object of the present invention is to provide a wiper insert having a built-in cutting depth.
SUMMARY OF THE INVENTION
These and other objects are realized by a cutting insert comprising an upper face, a lower face, and an edge face. An intersection between the upper face and the edge face forms six or eight cutting edges. The upper face defines a rake face, and the edge face defines a clearance face. The clearance face forms a clearance angle with a plane extending parallel to a center axis of the insert. Alternating ones of the cutting edges define major cutting edges separated by wiper edges. A first distance extending between two diametrically opposite wiper edges is larger than a second distance extending between two diametrically opposed major cutting edges. The first distance is 1% to 5% larger than the second distance.
The invention also relates to a milling cutter wherein at least two of the above described inserts are mounted in a holder.


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patent: 4616962 (1986-10-01), Ushijima
patent: 4954021 (1990-09-01), Tsujimura
patent: 4966500 (1990-10-01), Tsujimura et al.
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patent: 5876160 (1999-03-01), Johnson
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patent: 6079912 (2000-06-01), Rohthballer
patent: 6116824 (2000-09-01), Strand et al.

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