Cutters – for shaping – Including tool having plural alternatively usable cutting edges – With integral chip breaker – guide or deflector
Reexamination Certificate
2000-03-24
2001-12-11
Tsai, Henry (Department: 3722)
Cutters, for shaping
Including tool having plural alternatively usable cutting edges
With integral chip breaker, guide or deflector
C407S070000, C407S116000
Reexamination Certificate
active
06328504
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a cutting tip, and particularly to a plunge-cutting forming tip (for use with a turning tool; hereinafter the forming tip may be referred to merely as a tip) for plunge cutting while transferring onto a workpiece the contour (ridgeline) of a cutting edge.
2. Description of the Related Art
A circumferential surface of a bearing race (an outer circumferential surface of an inner race or an inner circumferential surface of an outer race) is subjected to plunge cutting in turning. A cutting tool is not fed along the axis of rotation of a workpiece (bearing race) during turning, but is fed radially. A plunge-cutting forming tip for use in such cutting differs in the shape of a cutting edge (the shape of a ridgeline of a cutting edge) according to individual type of workpiece, as is understood from the nature thereof.
For example, the plunge-cutting edge of a forming tip disclosed in Japanese Utility Model Application Laid-Open (kokai) No. 4-83503 has a profile to be transferred onto an outer circumferential surface of an inner race (workpiece). The forming tip is pressed against the circumferential surface of the workpiece to thereby plunge-cut, for example, a raceway groove for balls, a seal groove, or a chamfer of the circumferential surface. A chip breaker assuming a concave form is formed on a rake face through grinding so as to break chips produced during turning.
In plunge cutting of a raceway groove of a bearing and circumferential surfaces located at opposite sides of the raceway groove by means of such a forming tip, cutting of raceway groove begins first, followed by cutting of the circumferential surfaces together with the raceway groove. During cutting, the width and number of chips; i.e., the width of a cutting edge in contact with the workpiece and the number of points of contact with the workpiece, vary. Further, in general, such cutting produces relatively wide cutting chips and a large cutting force. Therefore, feed is set low, so that chips become relatively thin.
Since the rigidity of such a chip is poor, the direction of ejection of the chip becomes unstable, and thus the ejected chip tends to weave about. Further, the chip is less likely to break off. Accordingly, even when the ejected chip is curled, the chip does not break in an appropriate length. As a result, the chip tends to become excessively long while the direction of ejection of the chip is unstable. Such a chip may become entangled with a workpiece, potentially scratching a cut surface of the workpiece, or may become entangled with a tool or a chuck, potentially interrupting the continuous operation of a machine. Further, chip disposal has been difficult.
Since a chip breaker is formed on such a tip through grinding, the chip breaker fails to appropriately deform a chip. Even when a chip is coiled or coned, the coiled or coned chip hardly breaks and is wound coarsely, thus failing to reduce a volume thereof, with resultant poor chip disposal.
When, for example, a central raceway groove and seal grooves located at opposite sides of the central raceway groove are cut simultaneously by means of a forming tip, a chip is produced in association with cutting of the central raceway groove, and at the same time chips are produced in association with cutting of the seal grooves. Since chips are produced in a plurality of rows, they tend to become entangled with cut surfaces in a complicated manner or to become entangled with each other into the form of a bird's nest. Such entangled chips tend to become entangled with a chuck or to cause breakage of a cutting edge or stoppage of a machine. Thus, the conventional forming tip tends to involve entanglement of chips and chips in large lumps, causing poor chip disposal and impairing cutting efficiency.
SUMMARY OF THE INVENTION
The present invention addresses such a problem involved in turning by means of a forming tip, and an object of the present invention is to provide a cutting tip capable of improving chip disposal.
To solve the above problem, a cutting tip of the present invention is characterized in that a protrusion is disposed on a rake face in the vicinity of the ridgeline of a plunge-cutting edge.
In cutting by means of the plunge-cutting forming tip of the present invention, a chip is ejected which is not only merely thin, but also is ejected in such a manner as to be partially squeezed as a result of pressing against the protrusion. Accordingly, the chip is ejected such that a cross section thereof is deformed into a channel shape instead of assuming a flat shape. Thus, the rigidity of the chip is increased, so that chip disposal is improved accordingly. Preferably, the protrusion is located as close as possible to the ridgeline of the plunge-cutting edge (hereinafter may be referred to merely as “cutting edge”); specifically, is located not farther than 2 mm from the ridgeline. If the protrusion is located in excess of 2 mm from the ridgeline, the temperature of a chip becomes too low to impart effective deformation to the cross section of the chip.
A single protrusion may be disposed in the vicinity of the cutting edge, or a plurality of protrusions may be disposed along the ridgeline of the cutting edge. Through disposition of a plurality of protrusions, a chip assumes a corrugated cross section, thereby further improving its rigidity. When a plurality of protrusions are to be disposed on the rake face in the vicinity of and along the ridgeline of the plunge-cutting edge, the protrusions may be disposed substantially symmetrically or asymmetrically with respect to the lateral direction of the rake face. Notably, a lateral side of the rake face corresponds to the side of either end of the ridgeline of the cutting edge. Herein, the term “rear” or “rearward” refers to a direction opposite that of feed in plunge cutting. The term “front” or “frontward” refers to a direction opposite the rearward direction.
When the protrusions are disposed in a laterally symmetrical manner, a chip is ejected rearwardly and is thus readily curled on the rake face into a spiral form, thereby reducing its volume. When the protrusions are disposed in a laterally asymmetrical manner, the direction of ejecting a chip can be controlled accordingly, thereby reducing potential entanglement of chips.
The purpose for disposition of a protrusion is to deform a red-hot chip. Accordingly, a protrusion may assume the form of an independent island or the form of a peninsula extending from the rearward direction toward the ridgeline of the cutting edge. In the case of assuming the form of an independent island, the protrusion preferably assumes a substantially hemispherical form for convenience of manufacture, but may assume any other form. The height and width of protrusion may be selected according to the length of the ridgeline of the cutting edge and the width of the rake face and such that a chip is appropriately squeezed so as to assume a corrugated form.
The present invention is preferably embodied in the form of a tip adapted to cut a bearing race. In any one of the above-described plunge-cutting forming tips of the present invention, the plunge-cutting edge may be embodied in the form of a raceway-groove-cutting edge for cutting a raceway groove in a bearing race, in the form of a seal-groove-cutting edge for cutting a seal groove in a bearing race, or in the form of a combination of the raceway-groove-cutting edge and the seal-groove-cutting edge.
REFERENCES:
patent: 4214845 (1980-07-01), Mori
patent: 4273480 (1981-06-01), Shirai et al.
patent: 4832541 (1989-05-01), Noguchi et al.
patent: 5282703 (1994-02-01), Itaba et al.
patent: 5725334 (1998-03-01), Paya
patent: 0 775 544 A1 (1997-05-01), None
patent: 0135104 (1985-07-01), None
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European Search Report, No. EP 00 30 2368, dated Jul. 14, 2000.
NGK Spark Plug Co. Ltd.
Sughrue Mion Zinn Macpeak & Seas, PLLC
Tsai Henry
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