Cutters – for shaping – Including tool having plural alternatively usable cutting edges
Reexamination Certificate
1999-10-27
2001-09-18
Tsai, Henry (Department: 3722)
Cutters, for shaping
Including tool having plural alternatively usable cutting edges
C407S114000, C407S116000
Reexamination Certificate
active
06290436
ABSTRACT:
BACKGROUND AND SUMMARY
This invention relates to a cutting insert for rotating cutting tools of the type intended for chip-breaking metal machining. The rotating cutting tools include a part with a seat opening radially outwards for accommodating a cutting insert. The cutting insert is delimited by a top side, one or more cutting edges adjacent to the top side, an opposed bottom side, and one or more relief surfaces extending between the top side and the bottom side. The cutting insert is arranged to be fixed into the seat by means of a clamping element that may be pressed against its top side. A female recess and/or a male means is formed in the bottom side of the insert for co-operation with a suitable male means and/or a female recess in the tool part.
In the technology of chip-breaking metal machining by means of rotating cutting tools, there is a trend in development aimed at making it possible to run the tools at very high speeds of rotation. More specifically, this trend is directed to reducing a minimum the time required for different machining operations. Thus, in professional circles one reckons on running, e.g., milling cutters, bores and the like, at speeds of rotation up to the range of 20,000 to 30,000 rpm. In modem cutting tools, one uses replaceable cutting inserts made of extremely hard and wear-resistant materials, such as cemented carbide, ceramics or other compositions, e.g., with inclusions of diamond and cubic bore nitride, as means of machining. In for instance milling tools, such cutting inserts are often held in place by clamping elements, primarily wedges, instead of by means of screws. In the cases when the cutting insert is mounted into seats opening radially outwards (i.e., when using square shoulder facemills or facemills), then the cutting inserts represent a latent security risk, whenever the tool is run at a high rotation speed, in that the centrifugal force then becomes large.
The present invention aims at removing the above mentioned security risk and creating a cutting insert which in a reliable way is withheld in the appurtenant seat, even if the same under extreme conditions would tend to move radially outwards relative to the seat and the clamping element. A further object is to create a cutting insert that may be made of hard and sometimes brittle materials without running the risk of fracture if the same would be submitted to not only large centrifugal forces, but also large straining forces from the clamping element. It is also an object to create a cutting insert of a simple geometrical shape that makes possible a rational production by means of conventional production methods.
The present invention permits some or all of the foregoing objects to be achieved.
BRIEF ELUCIDATION OF PRIOR ART
In U.S. Pat. No. 5,658,101 a milling tool is disclosed that is suitable for the machining of wood or similar materials. The tool comprises a number of thin regrindable steel blades provided with cutting edges. The blades are clamped between, on the one hand, a support plate and, on the other hand, a clamping element in the form of a pressing plate that is pressable against the blade by means of a screw. In the blades with the cutting edge a through hole is provided. A male means in the form of a short tap is accommodated in the through hole and is coupled with the support plate. However, because the hole is a through hole, the hole may weaken a cutting insert intended for metal machining in an unacceptable way, such as where the insert is of the type that, on the one hand, is relatively small and, on the other hand, is made of materials that are considerably less tough than steel.
U.S. Pat. No. 4,396,315 discloses a cutting insert which, on a top side turned towards a clamping wedge, completely lacks any depression and which, on a bottom, side presents a conically shaped recess for receiving a fixing screw which is arranged to be tightened until it reaches the bottom of the conical recess. The purpose of this fixing screw is to position the cutting insert even after repeated grinding of the edges of the cutting insert. As a result of the screw being screwed down into the recess, the screw in its operative condition will not be smaller on all sides than the recess.
U.S. Pat. No. 5,558,142 discloses a cutting insert which in a topside has a depression which cooperates with a protrusion on a clamping wedge. This recess does not, however, have a V-shaped cross-sectional shape. Nor is the protrusion wedge-shaped in order to cooperate with a slanting flange surface in the manner stipulated by the present invention.
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Burns Doane Swecker & Mathis L.L.P.
Sandvik Aktiebolaget
Tsai Henry
LandOfFree
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