IE53483B1 - Cutting insert - Google Patents

Abstract

A polygonal cutting insert has an upper surface comprising two land areas 9, 13 located inwardly of a cutting edge. A descending wall 11 connects a first land 9 adjacent the cutting edge 7 and a secondary land 13 located below the cutting edge and joining a secondary descending wall 15 which joins a sloping floor 17 extending toward the center of the insert. The sloping floor descends, both as it extends toward the center of the insert, and as it extends away from the nearest corner parallel to the side of the polygonal insert.

Description

In metalworking operations, it is desirable to remove material as rapidly as possible in order to minimize manufacturing and labour cost. This requires that a cutting insert be designed that can stand up to the severe loads and heat generated at the high speeds, feed rates and depths of cut required to remove material rapidly.

It is also desirable that these inserts have a geometry that will minimize the power required in these metalworking operations by controlling the geometry of the chips produced. In addition, since not all applications require the same speed, depth of cut or feed rate, the insert chip control geometry should be capable of controlling chips over as wide a range of these parameters as possible.

Examples of prior insert .designs which have attempted to resolve these problems are disclosed in United States Patent No. 4,087,193 and Irish Patent No. 51899. The U.S. patent referred to discloses an indexable insert having a planar cutting edge land followed by a planar intermediate land below the cutting edge land. A secondary wall descends from the intermediate land to a planar floor which parallels the plane containing the cutting edges. According to this patent, the edge formed by the junction of the intermediate land and the secondary land acts to break chips as they slide over this edge. - 3 53483 The Irish patent mentioned above discloses an indexable insert having a planar cutting edge land followed by a descending wall terminating in a floor sloping downwardly as it extends toward the centre of the insert.

The present invention consists in a cutting insert comprising a hard wear resistant body having a peripheral wall and a top surface; a cutting edge formed by a juncture between said peripheral wall and said top surface; said top surface having a land area extending inwardly from said cutting edge, a wall descending as it extends inwardly from said land area, a secondary land area located inwardly of said descending wall, a secondary wall descending as it extends inwardly of said secondary land area, and a floor sloping downwardly as it extends inwardly of said secondary wall; and wherein the minimum height, X, of said secondary land area above said sloping floor is 15 to 30 mils.

Preferably, the insert is indexable and is composed of a cemented carbide. Most preferably, the insert is coated with a refractory oxide, nitride and/or carbide material.

It is also preferable that the sloping floor be symmetric about a plane containing the bisector of the insert corner angle. In this manner, at those high feed rates, beyond which the inner edge of the intermediate land area may be ineffective as a chipbreaker, the sloped floor can act to form a conical chip and thereby reduce power consumption.

Other subsidiary features of the present invention will become more apparent upon review of the drawings in conjunction with the following detailed description of one embodiment of the invention.

Figure 1 is a perspective view of an embodiment of a cutting insert according to the present invention.

Figure 2 is a view taken along arrows II-II in Figure showing a cross section along the nose angle bisector. Figure 3 is a view taken along arrows III-III in Figure 1 showing a cross section of the insert midway between the corners.

Referring to the drawings in more detail, it can be seen in Figure 1 that an indexable insert 1, according to the present invention, is shown. The insert comprises a polygonal hard wear resistant body having a peripheral wall 3 which forms a cutting edge 7 with the top surface 5 at the junction of the peripheral wall and top surface.

The cutting edge 7 is joined to a cutting edge land 9 ' which extends inwardly from the cutting edge. At the inner edge of the cutting edge land 9 is a descending wall 11 which descends inwardly and downwardly to a secondary 83483 - 5 land area 13. The secondary land area 13 also extends inwardly and joins a secondary wall 15. The secondary wall 15 joins a sloping floor 17 at its inner edge. The sloping floor 17 is symmetric about the bisectors of the corner angles. A bisector is shown in Figure 1 as line B-B.

As shown in Figure 1, this sloping floor 17 may join a planar floor 19 which is most preferably parallel to a plane formed by the cutting edges 7. In the centre of the insert, an insert aperture 21 may be provided for receiving a locking pin or screw.

Referring to Figure 2, which is a cross section of the insert taken along line B-B, which was mentioned before as the bisector of one of the corner angles of the insert, it can be seen that the descending wall 11 forms an angle with the plane defined by the cutting edges 7. This angle A is most preferably, however, 20 to 12 degrees. The descending wall 11 joins the secondary land area 13 at an angle B of 155 to 170 degrees.

It can also be seen in this figure that the sloping floor 17 forms an angle with a plane parallel to the cutting edge plane. This angle D should be between 1 to 10 degrees and, also, in viewing this figure, it can be seen that the sloping floor 17 makes its closest approach to the secondary land area 13 in the corner area. This - 6 distance is shown by the symbol X in Figure 2.

Referring now to Figure 3, which is a cross section through the insert intermediate the corners, it can be seen that, as the sloping floor 17 extends away from the corner areas, it slopes downwardly parallel to the sides of the insert until it joins the planar floor 19. The maximum change in height, H, of the sloped floor 17 from the corner area to the planar floor 19 should be between 5 and 15 mils.

The design of the sloped floor 17 in conjunction with the angle C formed by the secondary land area 13 and the secondary descending wall 15 helps to form a conical chip on very high feed rates and thereby minimizes power consumption required in metalworking at those high feed rates in which the chip will slide down wall 15 and contact the sloped floor 17.

It is believed that angle C should be between 140 and 160 degrees to produce optimum results. The distance X should be 15 to 30 mils.

These embodiments shown in Figures 1 through 3 are only illustrative of the many possible embodiments that are within the scope of the appended claims.

Claims (11)

CLAIMS:

1. A cutting insert comprising a hard wear resistant body having a peripheral wall and a top surface; a cutting edge formed by a juncture between said peripheral wall and said top surface; said top surface having a land area extending inwardly from said cutting edge, a wall descending as it extends inwardly from said land area, a secondary land area located inwardly of said descending wall, a secondary wall descending as it extends inwardly of said secondary land area, and a floor sloping downwardly as it extends inwardly of said secondary wall; and wherein the minimum height, X, of said secondary land area above said sloping floor is 15 to 30 mils.

2. A cutting insert according to Claim 1 wherein said body has a polygonal shape when viewed in top view; said sloping floor sloping downwardly as it extends away from the nearest corner of said polygonal shape parallel to the sides of the said polygonal shape.

3. A cutting insert according to Claim 1 further comprising a planar floor extending inwardly from said sloping floor and defining a plane oblique to said sloping floor.

4. A cutting insert according to Claim 1 wherein said sloping floor is obliquely related to a plane defined by said land area.

5. A cutting insert according to Claim 1 wherein said top surface is polygonal in nature and said cutting edge and peripheral wall define the sides and corners of said polygon. 5

6. A cutting insert according to Claim 5 wherein the height of said land area above the outermost end of said sloping floor is a minimum in said corners.

7. A cutting insert according to Claim 1 wherein said land area is substantially planar and said descending 10 wall slopes downwardly from said land area at an angle of 12 to 20 degrees.

8. A cutting insert according to Claim 7 wherein said secondary land area is substantially planar and substantially parallel to said land area, and wherein said 15 descending wall and said secondary land area form an included angle of 155 to 170 degrees.

9. A cutting insert according to Claims 1, 7 or 8 wherein said sloped floor has a vertical height change of 5 to 15 mils from highest to lowest point. 20

10. A cutting insert according to Claim 2 wherein said sloping floor is symmetric about a plane containing the bisector of the angle formed by said nearest corner.

11. A cutting insert according to Claim 1 wherein said sloping floor slopes downwardly at an angle, D, of 1 25 to 10 degrees. 33483