Cutters – for shaping – Rotary cutting tool – Including holder having seat for inserted tool
Patent
1998-04-09
2000-04-25
Tsai, Henry W. H.
Cutters, for shaping
Rotary cutting tool
Including holder having seat for inserted tool
407 43, 407 47, 407 64, B23C 520
Patent
active
060536713
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The present invention relates to a cutting tool for chip forming machining preferably for milling, comprising a holder and a cutting insert, said cutting insert having a generally circular basic shape and including at least one cutting edge created by the transition between an upper face and an edge face of the cutting insert, said upper face being a rake face and said edge face being a clearance face, said holder and cutting insert having first means for preventing rotation of the insert about a center axis. The invention further relates to a cutting insert and a method for preventing rotation of a cutting insert.
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 has no shim, an insert fracture often gives rise to damages of the tool body. In order to avoid such damages 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.
Riviere U.S. Pat. No. 5,147,158 discloses a polygonal cutting insert having an integrated shim so as to provide a fracture zone.
Rescigno U.S. Pat. No. 5,346,336 shows a circular metal cutting insert provided with five equidistant flat facets on the clearance surface. The facets are provided to constitute defined positions when indexing the cutting insert. Each facet forms an acute angle relative to the central axis of the cutting insert. A retention screw secures the insert to the insert seat of a holder. In the known tool, friction is not a major contributor against unwanted rotation of the insert. The locating surfaces of the insert will be worn such that the position of the insert in the seat will be increasingly less accurate during use. Furthermore the known insert lacks fracture zones so as to prevent an insert breakage from transferring into the seat or shim.
OBJECTS OF THE INVENTION
One object of the present invention is to present a cutting insert that overcomes the disadvantages discussed above.
Another object of the present invention is to provide a cutting insert, a cutting tool and a method including means adapted for a double retention against rotation of the insert.
Still another object of the present invention is to provide a cutting insert having an integrated shim performing three different functions, namely fracture, rotational and indexing control.
SUMMARY OF THE INVENTION
These and other objects are realized by a cutting insert for chip forming machining. The insert comprises a body having a generally circular upper face, a lower face, and an edge face interconnecting the upper and lower faces. A transition between the upper face and the edge face forms a cutting edge. The edge face includes upper and lower portions separated by a step whereby a perpendicular distance from a center axis of the body to the edge face is greater above the step than below the step. The upper portion is generally frustoconical and tapers in a downward direction. The lower portion is disposed closer to the lower face than to the upper face and is spaced radially inwardly of a downward projection of the generally frustoconical upper portion. A first height extending from the lower face to an intersection of the step with the lower portion is from 15-60% of a second height extending from the lower face to the cutting edge.
Preferably, a perpendicular distance from the center axis to the lower portion of the edge face is nonuniform around the perimeter of the lower portion.
The invention also relates to the combination of a cutting tool and a cutting insert, and to a method
REFERENCES:
patent: 1838520 (1931-12-01), Archer
patent: 4812087 (1989-03-01), Stashko
patent: 5147158 (1992-09-01), Rivere
patent: 5236288 (1993-08-01), Flueckiger
patent: 5346336 (1994-09-01), Rescigno
patent: 5536119 (1996-07-01), Werner et al.
patent: 5827016 (1998-10-01), Strand
patent: 5855457 (1999-01-01), Arai et al.
Eklund Sven
Riviere Bertrand
Stedt Robert
Seco Tools AB
Tsai Henry W. H.
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