Claims:1. A double-sided, polygonal cutting insert (10), comprising:
a first surface (12);
a second surface (14) opposite the first surface (12);
a plurality of side surfaces (16) extending between the first surface (12) and the second surface (14), each side surface (16) is perpendicular to the first surface (12) and the second surface (14);
a plurality of primary cutting edges (18) formed at an intersection between the plurality of side surfaces (16) and the first surface (12); and
a plurality of wiper edges (19) formed at an intersection between the plurality of side surfaces (16) and the first surface (12), each wiper edge (19) having a step (34) protruding radially outward from a respective side surface and formed with a radius, R1.

2. The cutting insert according to Claim 1, wherein the radius, R1, is between 100 mm and 1000 mm.

3. The cutting insert according to Claim 1, wherein the plurality of primary cutting edges (18) and the plurality of wiper edges (19) are arranged in an alternating fashion.

4. The cutting insert according to Claim 1, wherein the second surface (14) is identical to the first surface (12).

5. The cutting insert according to Claim 1, further comprising a plurality of corner radiuses (20) extending between the first and second surfaces (12, 14) and each of the plurality of side surfaces (16).

6. The cutting insert according to Claim 5, wherein each of the plurality of corner radiuses (20) are identical to each other.

7. The cutting insert according to Claim 5, wherein each primary cutting edge (18) and each wiper edge (19) has a length, CL, that extends from one of the corner radiuses (20) to an adjacent corner radius (20).

8. The cutting insert according to Claim 1, wherein a length, CL, of each primary cutting edge (18) and each wiper edge (19) is described by the following equation:
CL=ICtan(22.5)-CR,
where,
IC is a diameter of an inscribed circle of the cutting insert, and
CR is equal to a magnitude of the corner radius.

9. A double-sided, polygonal cutting insert (10), comprising:
a first surface (12);
a second surface (14) opposite the first surface (12);
a plurality of side surfaces (16) extending between the first surface (12) and the second surface (14);
a plurality of primary cutting edges (18) formed at an intersection between the plurality of side surfaces (16) and the first surface (12), and a plurality of primary cutting edges (18) formed at an intersection between the plurality of side surfaces (16) and the second surface (14); and
a plurality of wiper edges (19) formed at an intersection between the plurality of side surfaces (16) and the first surface (12) and a plurality of wiper edges (19) formed at an intersection between the plurality of side surfaces (16) and the second surface (14), each wiper edge (19) having a step (34) extending radially outward from a respective side surface and formed with a radius, R1.

10. The cutting insert according to Claim 9, wherein the radius, R1, is between 100 mm and 1000 mm.

11. The cutting insert according to Claim 9, wherein the plurality of primary cutting edges (18) and the plurality of wiper edges (19) are arranged in an alternating fashion.

12. The cutting insert according to Claim 9, further comprising a plurality of corner radiuses (20) extending between the first and second surfaces (12, 14) and each of the plurality of side surfaces (16).

13. The cutting insert according to Claim 12, wherein each of the plurality of corner radiuses (20) are identical to each other.

14. The cutting insert according to Claim 12, wherein each primary cutting edge (18) and each wiper edge (19) has a length, CL, that extends from one of the corner radiuses (20) to an adjacent corner radius (20).

15. The cutting insert according to Claim 9, wherein a length, CL, of each primary cutting edge (18) and each wiper edge (19) is described by the following equation:
CL=ICtan(22.5)-CR,
where,
IC is a diameter of an inscribed circle of the cutting insert, and
CR is equal to a magnitude of the corner radius.

16. A cutting tool (100) comprising a tool body (102) having a plurality of pockets (116) for mounting a cutting insert (10) as recited in Claim 1, wherein at least one primary cutting edge (18) of a first cutting insert (10) mounted in a first pocket (116) and at least one wiper edge (19) of a second cutting insert (10) mounted in a second pocket (116) contact a workpiece (200) during a cutting operation, thereby producing a high-quality surface finish on the workpiece (200).
, Description: The invention pertains to the field of indexable cutting inserts. More particularly, the invention pertains to an indexable, double sided, polygonal cutting insert with alternating cutting edges and wiper edges.

DESCRIPTION OF RELATED ART
Modern high-performance cutting tools use replaceable and typically indexable inserts owing to the high cutting speeds and feeds supported by the superior insert materials. Common materials for inserts include tungsten carbide, polycrystalline diamond and cubic boron nitride.
Indexable inserts use a symmetrical polygonal shape, such that when the first cutting edge is blunt they can be rotated or flipped over, presenting a fresh cutting edge which is accurately located at the same geometrical position. Geometrical repeatability saves time in manufacturing by allowing periodical cutting edge renewal without the need for tool grinding, setup changes, or entering of new values into a CNC program.
Common shapes of indexable inserts include square, triangular and rhombus (diamond) providing four, three and two cutting edges, respectively, on each side of the insert. A double-sided or invertible square insert, for example, can be flipped over to provide eight cutting edges.
The number of cutting edges is directly related to the cost per edge of the cutting insert. The more cutting edges that are available, the more the cutting insert has value. Thus, it is desirable to provide a cutting insert with multiple cutting edges. In addition, it is desirable for a cutting insert that provide a high-quality surface finish.

SUMMARY OF THE INVENTION
The problem of reducing the cost of the cutting insert and providing a high-quality surface finish is solved by providing a double-sided, indexable, polygonal cutting insert that has alternating primary cutting edges and wiper edges. All the primary cutting edges and wiper edges can be used in a single right hand style milling cutter, which provides a true cutting and wiper insert.
In one aspect of the invention, a double-sided, polygonal cutting insert, comprising: a first surface; a second surface opposite the first surface; a plurality of side surfaces extending between the first surface and the second surface, each side surface is perpendicular to the first surface and the second surface; a plurality of primary cutting edges formed at an intersection between the plurality of side surfaces and the first surface; a plurality of wiper edges formed at an intersection between the plurality of side surfaces and the first surface, each wiper edge having a step extending radially outward from a respective side surface and formed with a radius, R1.
In another aspect of the invention, a double-sided, polygonal cutting insert, comprising: a first surface; a second surface opposite the first surface; a plurality of side surfaces extending between the first surface and the second surface; a plurality of primary cutting edges formed at an intersection between the plurality of side surfaces and the first surface and a plurality of primary cutting edges formed at an intersection between the plurality of side surfaces and the second surface; a plurality of wiper edges formed at an intersection between the plurality of side surfaces and the first surface and a plurality of wiper edges formed at an intersection between the plurality of side surfaces and the second surface, each wiper edge having a step extending radially outward from a respective side surface and formed with a radius, R1.
In yet another aspect of the invention, a cutting tool comprises a tool body having a plurality of pockets for mounting a cutting insert as recited in Claim 1, wherein at least one primary cutting edge of a first cutting insert mounted in a first pocket and at least one wiper edge of a second cutting insert mounted in a second pocket contact a workpiece during a cutting operation, thereby producing a high-quality surface finish on the workpiece.

BRIEF DESCRIPTION OF THE DRAWINGS
While various embodiments of the invention are illustrated, the particular embodiments shown should not be construed to limit the claims. It is anticipated that various changes and modifications may be made without departing from the scope of this invention.
FIG. 1 is an isometric view of a first surface of a cutting insert in accordance with an embodiment of the invention;
FIG. 2 is an isometric view of a second surface of the cutting insert of FIG. 1;
FIG. 3 is a top view of the cutting insert of FIG. 1;
FIG. 4 is another top view of the cutting insert of FIG. 1;
FIG. 5 is a cross-sectional view of the cutting insert taken along line 5-5 of FIG. 4;
FIG. 6 is a cross-sectional view of the cutting insert taken along line 6-6 of FIG. 4;
FIG. 7 is a front view of a cutting tool, such as a milling cutter, with the cutting insert of FIG. 1 mounted in the pockets of the cutting tool; and
FIG. 8 is an enlarged view of the cutting insert of FIG. 1 mounted in the pocket of the cutting tool.

DETAILED DESCRIPTION OF THE INVENTION
Referring now to FIGS. 1-6, a cutting insert 10 is generally shown according to an embodiment of the invention. In general, the cutting insert 10 comprises a double-sided, polygonal cutting insert. Although other geometric shapes are possible, the cutting insert 10 is of a generally octagonal shape that is symmetric about a central axis 24 and includes four primary cutting edges and four wiper edges on each side for a total of eight primary cutting edges and eight wiper edges. However, it will be appreciated that the invention can be practiced with any multiple number of primary cutting edges and wiper edges, so long as the number of primary cutting edges is approximately equal to the number of wiper edges.
Referring now to FIGS. 1 and 2, the cutting insert 10 includes a first surface 12, a second surface 14 on an opposite side with respect to the first surface 14 and a plurality of side surfaces 16 extending between the first surface 12 and the second surface 14. Because the cutting insert 10 is symmetric about all three axes (x-, y-, z-), only the first surface 12 will be described in detail herein for brevity. However, it will be appreciated that any discussion of the first surface 12 applies to the second surface 14.
In the illustrated embodiment, each side surface 16 is substantially perpendicular to both the first and second surfaces 12, 14. In other words, the first and second surfaces 12, 14 are substantially parallel to each other and perpendicular to the side surfaces 16. That is, the side surfaces 16 have a facet clearance angle of zero degrees. Thus, both the first and second surfaces 12, 14 of the cutting insert 10 can be presented to the workpiece 200 (FIG. 8). In the illustrated embodiment, the cutting insert 10 has a total of eight side surfaces 16. Each side surface 16 is identical to each other. Thus, only one side surface 16 will be described herein for brevity, and it will be appreciated that any description herein of one of the side surfaces 16 applies to all the side surfaces 16.
A primary cutting edge 18 is formed at the intersection between the first surface 12 and a respective side surface 16 for a total of four primary cutting edges 18. In addition, a primary cutting edge 18 is formed at the intersection between the second surface 14 and a respective side surface 16 for a total of four additional primary cutting edges 18 (i.e. a total of eight primary cutting edges 18 for the cutting insert 10). Each cutting edge 18 is identical to each other. Thus, only one cutting edge 18 will be described herein for brevity, and it will be appreciated that any description herein of one primary cutting edge 18 applies to all the primary cutting edges 18.
Similarly, a wiper edge 19 is formed at the intersection between the first surface 12 and a respective side surface 16 for a total of four wiper edges 18. In addition, a wiper edge 19 is formed at the intersection between the second surface 14 and a respective side surface 16 for a total of four additional wiper edges 19 (i.e. a total of eight wiper edges 19 for the cutting insert 10). Each cutting edge 19 is identical to each other. Thus, only one cutting edge 19 will be described herein for brevity, and it will be appreciated that any description herein of one wiper edge 19 applies to all the wiper edges 19.
As can be seen in FIGS. 1-3, each primary cutting edge 18 is separated by a wiper edge 19. That is, the primary cutting edges 18 and the wiper edges 19 are arranged in an alternating fashion on the same side of the cutting insert 10. In addition, the intersection of the first surface 12 and a respective side surface 16 that forms the primary cutting edge 18 also forms the wiper edge 19 at the intersection of the second surface 14 and the same respective side surface 16. Thus, the primary cutting edges 18 and the wiper edges 19 alternate between the first surface 12 and the second surface 14.
Because the cutting insert 10 has an even number of sides 16, there are an identical number of primary cutting edges 18 and wiper edges 19. However, it should be appreciated that the primary cutting edges 18 and the wiper edges 19 can be different in number and arranged in a non-alternating fashion. For example, for a pentagon-shaped cutting insert having five sides 16, the cutting insert may have three primary cutting edges 18 and two wiper edges 19.
A corner radius 20 connects each side surface 16 and extends between the first surface 12 and the second surface 14. Preferably, each corner radius 20 has a radius in the range between approximately 0.5 mm to approximately 3.0 mm. For example, the corner radius 20 may have a radius of about 2.0 mm (0.08 inches). Because each corner radius 20 is substantially identical to each other, only one corner radius 20 is discussed herein for brevity, and it will be appreciated that any description herein of one corner radius 20 applies to all corner radiuses 20.
The cutting insert 10 also includes a countersunk bore 22 extending through the first and second surfaces 12, 14, and a central, longitudinal axis 24. It should be appreciated that the cutting insert is mirror symmetric about all three axes (x-, y- and z-axes). As a result, the cutting insert 10 comprises a double-sided cutting insert in which all sixteen cutting edges 18, 19 at the intersection between the side surfaces 16 and each of the first and second surfaces 12, 14 can separately be used in a machining operation.
The first surface 12 (and the second surface 14) has a topography including a substantially planar central region 26 surrounding the countersunk bore 22. The central region 26 extends from the countersunk bore 22 and terminates in an irregular-shaped boundary 28. The first surface 12 also includes a rake face 30 extending radially inward from each cutting edge 18. As shown in FIGS. 5 and 6, each rake face 30 has a concave topography and is lower in elevation than the central region 26. The rake faces 30 associated with the wiper edges 19 may include unique indicia 32 to identify the wiper edge 19. Alternatively, the rake faces 30 associated with the primary cutting edges 18 may include the unique indicia 32, or both the primary cutting edges 18 and the wiper edges 19 may include the unique indicia 32.
Each primary cutting edge 18 and each wiper edge 19 has a cutting-edge length, CL, given by:
(1)
where,
IC is the diameter of an inscribed circle of the cutting insert 10;
#CE is the number of cutting edges 18, 19 (i.e. equal to 8); and
CR is the magnitude of the corner radius 20. For example, for a corner radius equal to 2.0 mm, CR is equal to 2.0.
Thus, for the octagon cutting insert 10 of the illustrated embodiment, the #CE is equal to 8. Thus, each cutting edge 18, 19 of the cutting insert 10 has a cutting-edge length, CL, given by:
CL=ICtan(22.5)-CR (2)
An inscribed circle is the largest possible circle that can be drawn inside the cutting insert 10. It should be appreciated that for a polygon, a circle is not actually inscribed unless each side 16 of the cutting insert 10 is tangent to the circle. For a regular polygon, such as the cutting insert 10, an inscribed circle touches the midpoint of each side 16. By contrast, a circumscribed circle touches the corner radius 20 between each side 16 of the cutting insert 10. As will be appreciated, the diameter of the inscribed circle is a function of the size of the cutting insert 10. The larger the cutting insert 10, the larger the diameter of the inscribed circle that can be drawn to touch each of the cutting edges 18.
As shown in FIGS. 3 and 4, the inscribed circle related to the primary cutting edges 18 has a first diameter, D1, and the inscribed circle related to the wiper edges 19 has a second diameter, D2, which is slightly larger than the first diameter, D1. In one embodiment, the first diameter, D1, is approximately 20.0 mm (0.787 inches) and the second diameter, D2, is approximately 20.2 mm (0.795 inches). The larger, second diameter, D2, is a result of the wiper edges 19 being formed with a step 34 protruding radially outward from the side surface 16. The step 34 is formed with a very large radius, R1, as shown in FIGS. 1 and 2. In one embodiment, the radius, R1, has a range between about 100 mm to about 1000 mm, depending on the application and the capability of the milling cutter. For example, in one embodiment, the radius, R1, is about 325 mm (12.79 inches).
Referring now to FIGS. 7 and 8, a cutting tool 100, for example, a milling cutter, is shown according to an embodiment of the invention. The milling cutter 100 comprises a tool body 112 including a cutting end 114 with a plurality of circumferentially-spaced pockets 116, and a mounting end 118 opposite the cutting end 114. The tool body 112 is designed to be rotatably driven about a central longitudinal axis 113. In the illustrated embodiment, the milling cutter 100 is commonly known as a right-hand milling cutter and includes a total of six pockets 116. However, it will be appreciated that the invention is not limited by the number of pockets 116, and that the invention can be practiced with any desirable number of pockets that provide the desired cutting capabilities. Each of the pockets 116 can receive a cutting insert 10, which is securely held in the pocket 116 by means of a mounting screw 119.
The side surfaces 16 of the cutting insert 10 engage the pocket 116 when the cutting insert 10 is mounted in the tool body 112 during cutting operations. Preferably, one of the first and second surfaces 12, 14 and at least two side surfaces 16 should engage the tool body 112 when the cutting insert 10 is properly indexed in the tool body 112. It will be appreciated that each of the cutting edges 18, 19 can be indexed into an active position and effectively utilized in the milling cutter 100 (FIGS. 7 and 8). It will be appreciated that the number of cutting edges 18, 19 and the number of times that the cutting insert 10 can be indexed depends on the geometric shape of the cutting insert 10. In general, the number of times the cutting insert 10 of the invention can be indexed is equal to the total number of cutting edges 18, 19. Thus, the cutting insert 10 of the invention can be indexed sixteen times, unlike conventional rectangular or square cutting inserts with fewer number of cutting edges.
The cutting insert 10 of the invention can be mounted in a respective pocket 116 of the milling cutter 100 such that a primary cutting edge 18 contacts the workpiece 200, and another cutting insert 10 can be mounted in a respective pocket 116 of the milling cutter 100 such that a wiper edge 18 contacts the workpiece 200. In this manner, the primary cutting edges 18 produce a rough cut of the workpiece 200, while the wiper edges 19 produce a high-quality surface finish on the workpiece 200. For example, in a milling cutter with a total of six pockets 116, three of the cutting inserts 10 can be mounted in a respective pocket 116 such that the primary cutting edge 18 contacts the workpiece 200, and the other three of the cutting inserts 10 can be mounted in a respective pocket 116 such that the wiper edge 19 contacts the workpiece 200, thereby producing a high-quality surface finish on the workpiece 200.
The patents and publications referred to herein are hereby incorporated by reference.
Having described presently preferred embodiments the invention may be otherwise embodied within the scope of the appended claims.