Cutters – for shaping – With chip breaker – guide or deflector – Comprising concave surface in cutting face of tool
Reexamination Certificate
2000-03-03
2001-08-14
Tsai, Henry (Department: 3722)
Cutters, for shaping
With chip breaker, guide or deflector
Comprising concave surface in cutting face of tool
C407S117000, C407S120000
Reexamination Certificate
active
06273651
ABSTRACT:
CROSS REFERENCE TO RELATED APPLICATIONS
This application is the US national phase of PCT application PCT/DE98/02635 filed Sep. 2, 1998 with a claim to the priority of German application 19739300.4 filed Sep. 8, 1997.
FIELD OF THE INVENTION
The invention relates to a cutting insert for cutting profiles, in particular for milling profiled grooves in rotating workpieces such as crank shafts, by means of a generally parallepipedal base body having at least two usable cutting edges and two parallel planar side faces that are traversed by a mounting hole or provided with a seat for engaging a clamping arm, two edge faces that have on their opposite ends respective cutting faces bounded by a cutting edge shaped like the profile to be made, and two free faces between the opposite cutting edges.
BACKGROUND OF THE INVENTION
In the finishing of crank or cam shafts a number of different milling operations are used, the movements for the milling operations to be performed being made complex by the partially eccentric bearing or shaft pins. Ia system described for example in German 195 46 196 a workpiece, for example a crank shaft, is held with its ends in rotatably driven chucks such that it is rotatable about its central longitudinal axis. High-speed disk which are rotatable on a support are used for machining so that the workpiece can be followed.
In order to make a complete shape that is formed of a pair of undercut fillets and a machined pin, different cutting bodies are used to produce the undercut fillet and the cylindrical shape than are used for machining the pin of a crank-shaft bearing support. In order to make the undercut fillets the above-described cutting insert is used. The cutting inserts in question are secured by mounting screws in tool holders, and millers have cassettes with seats in which the cutting inserts are set and secured by a mounting screw.
Further uses of the above-described cutting inserts are in copy lathing.
With cutting inserts of the above-described type there are particular difficulties when an insufficient free angle is available for optimizing the radial and/or axial position. An increase in the free angle by minimizing the flank angle leads to overloading of the cutting edge. The likelihood of premature breakage of the cutting edge reduces the service life of the tool. The profile to be milled causes forces to be exerted in different directions on the cutting insert, making a stable mounting of the cutting insert in its seat difficult.
OBJECT OF THE INVENTION
It is therefore an object of the present invention to provide a cutting insert of the above-described type that is sure to have a flexible mounting position with optimal angling of the cutting insert and which performs plunge milling operations better than the prior-art cutting inserts.
SUMMARY OF THE INVENTION
This object is attained by a cutting insert wherein the free faces are at least partially circularly arcuately concave. The concave formation of the free face increases the free angle and produces toward the middle of the free face a large empty space, that is a spacing from the workpiece being milled that can be preferably 0.3 to 1 mm and that permits the desired tipping of the cutting insert relative to the workpiece.
Thus the cutting edge is arcuate, preferably having a projecting convexly curved part and an immediately adjacent concavely curved part so that for example the convex part serves to cut the fillet and the concave part the radial transition from the fillet to the adjacent cylindrical surface. Other cutting-edge profiles are possible according to the invention up to and including a multi-tooth cutting edge.
To further stabilize the cutting edge preferably a face region immediately adjacent the convex cutting edge part extends at a free angle of 0° while the adjacent free-face region is concave. In addition to stabilizing the cutting edge at the front the 0° free-face shape serves as rear abutment face of the cutting insert in the holder seat. The negative free-face region is thus restricted along the convex cutting-edge part in its width as in its height, which preferably lie between 0.2 and 2 mm.
According to a further embodiment of the invention the radii of curvature other than those of the free-face region are shave centers are generally so shaped through the profile region of the cutting-edge parts that their centers lie on a common vertical axis (perpendicular to the extended support surface of the cutting insert). The cutting face can be formed as a cutting-face recess, convex, planar at the cutting edge, with a positive, negative, or 0° cutting angle. If the recess shape is used, measured parallel to a longitudinal axis, the cutting angle of one of the cutting-face recesses is along the entire cutting edge between 0° and 30°, preferably 20°. In this manner except at the cutting-edge region with the 0° free-face region, there are sharp cutting edges with a relatively strongly wedge angle.
According to a further embodiment of the invention the cutting edge is of wavy shape, a line running along the wavy edge having convex and concave parts. This embodiments covers profile cutting plates with multiple teeth in single or double models where the upper and the lower edges are used for machining. The teeth formed by the wavy cutting-edge shape have flank angles between 5° and 25°. In this manner there are several small-radius main and auxiliary cutting edges that are arrayed one after the other on plunging of the tool into the workpiece and that with each successive advance served to progressively smooth the cut surface which is later subjected to polishing.
According to a further embodiment of the invention there are overall eight usable cutting edges in a cutting insert formed mirror symmetrical to a plane parallel to one of the two outer edge faces. In this way and manner the cutting edges on one side of the cutting insert can be used for the left-hand undercut fillets and the two other for right-hand undercuts. The same is true for the four cutters at the opposite end.
It is furthermore possible to form the cutting faces with concave and/or convex chip-shaping elements, that is chip-shaping grooves, hollows, and/or bumps which are known in the prior art, as for example ribs or elongated grooves that lift and deflect the chip. The cutting insert has according to the selected cutting direction either a hole for receiving a mounting screw or a recess for a clamping arm or dog.
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patent: 4669925 (1987-06-01), Lowe et al.
patent: 5032050 (1991-07-01), Niebauer et al.
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patent: WO 90/14930 (1990-12-01), None
patent: WO 94/27768 (1994-12-01), None
patent: WO 95/25618 (1995-09-01), None
Heinloth Markus
Zastrozynski Jürgen
Dubno Herbert
Tsai Henry
Widia GmbH
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