GB2254026A - Cutting insert - Google Patents

Abstract

The cutting insert (12) is provided with a cutting surface (14) and adjacent this surface a chip breaker (20) which is spaced from the cutting surface by a land (22) which land is shaped to guide swarf generated during the machining towards a sloping surface. The insert (12) is provided with a protrusion (24) from the land (22) so that, in use, swarf originating from the cutting action of the cutting surface during machining is deflected and broken up by the protrusion. <IMAGE>

Description

CUTTING INSERT Field of the Invention The present invention relates to cutting inserts.

Rackglsound to the Invention Cutting inserts are well known for use in a wide variety of machining applications. The inserts are normally mounted in a holder, relative movement is provided between the insert and a work piece, and the insert is brought into contact with the work piece (or vice versa). The cutting action of the insert generates, from most materials, a thread of waste material known as "swarf", sometimes the swarf will comprise shorter lengths of waste material, say 10 centimetres long.

Swarf usually has very sharp edges which makes it a safety hazard. A lot of swarf, by volume, can be produced relatively quickly which can cause problems by clogging machinery, by obstructing the work piece from the sight of an operator and/or by requiring the provision of complex swarf clearance devices.

In an attempt to overcome these problems it is known to provide a cutting insert with a single so-called "chip breaker" adjacent a cutting surface of the insert. Known chip breakers (see Figures 1 and 2) normally comprise a sloping surface 2 spaced from a cutting surface 4 of an insert 6 by a land 8 which is shaped to guide the swarf 10 towards the sloping surface 2. When the swarf 10 reaches the sloping surface of the chip breaker it is deflected away from the insert 6. This change of direction is intended to be sufficient to bend the swarf so that it is broken into a multiplicity of short lengths (e.g about 3 millimetres long). These short lengths can be dealt with far more easily.

For many years this method of dealing with cutting insert swarf has been accepted as the norm, despite the fact that in many instances the swarf has not been broken up into lengths that are sufficiently short to overcome the difficulties referred to above.

This problem has been especially, though not exclusively, prevalent when using thread or groove cutting inserts.

It is an aim of the present invention to alleviate or obviate the problem described above.

Summarv of the Invention According to the present invention, there is provided a cutting insert comprising a body having a cutting surface, a chip breaker spaced from the cutting surface by a land, and a protrusion from the land between the chip breaker and the cutting surface; whereby, in use, swarf originating from the cutting action of the cutting surface is deflected by the protrusion. By deflecting the swarf before it reaches the chip breaker a much higher percentage of the swarf is broken-up compared with the percentages obtained using known inserts.

Preferably the protrusion comprises a sloping face; this is advantageous as it provides deflection and can be readily manufactured.

A "sloping" face is a face that is neither perpendicular nor reentrant relative to the land; it makes an obtuse angle to the land (measured between the open surfaces).

The sloping face preferably makes an obtuse angle to the chip breaker surface. This arrangement provides deflection in two different directions which is currently believed to enhance the operation of the present invention.

Conveniently, the protrusion comprises two sloping surfaces converging together towards the cutting surface. This construction provides for deflection of the majority of the swarf by the protrusion.

The divergent ends of the protrusion surfaces are preferably joined by a convex surface; the protrusion may form the general shape of a pointed "tear drop" in section. This configuration combines manufacturing convenience with rigidity of structure.

The invention will now be described, by way of example only, with reference to the drawings that follow; in which: Brief Descrintion of the Drawings Figure 1 is a plan view of a known cutting insert.

Figure 2 is a side view of the known insert shown in Figure 1 from the direction marked II.

Figure 3 is a plan view of a cutting insert in accordance with the present invention.

Figure 4 is a side view of the cutting insert shown in Figure 3 from the direction marked IV.

Figure 5 is a section on the line V-V in Figure 3.

Figure 6 is a sectional view on the line VI-VI in Figure 3.

Figure 7 is a fragmentary view of the protrusion shown in Figures 3-5.

Figure 8 shows the finally machined insert.

All of the above Figures illustrate enlarged representations of approximately -eight-times magnification; Figure 7 is enlarged to a greater scale to show the detail more clearly.

Descrintion of the Preferred Embodiment Referring now to Figures 3-6 of the drawings that follow, there is shown a cutting insert 12 comprising a body 13 having three cutting surfaces 14. The insert 12 is of generally rectangular shape (in plan) with a cutting surface 14 substantially at each vertex thereof. There are a wide variety of cutting surfaces that may be used with cutting inserts. The insert 12 shown in Figures 3-6 and described herein is suitable for use in the manufacture of external right-hand threading and grooving; however, the invention is applicable to most cutting inserts as will be appreciated by those skilled in the art.

The insert 12 includes two substantially parallel generally triangular faces 16 joined by substantially similar side walls 18.

The cutting surfaces 14 are formed by the intersections of two side walls 18 and a face 16 (this face is hereinafter known as the upper face 16a, the opposite face is referred to as lower face 16b), i.e at the vertices of the body 13. The cutting surfaces 14 may be used for some time since they are, at least partially selfsharpening.

Each cutting surface 14 is spaced from a chip breaker 20 by a land 22. Between the chip breaker 20 and the cutting surface 14 there is a protrusion 24 from the land 22.

Concentrating now on one of the similar corners of the inserts 12 for simplicity of explanation.

The chip breaker 20 is known in the art per aç, it comprises a sloping face 26 extending from one side wall 18 to another side wall 18, it may be considered to be isolating a corner of the insert 12 from the remainder thereof. The sloping face 26 includes a bend 28, approximately three-fifths along the length of the sloping face 26 inwards towards the body 13. The sloping face 26 is substantially planar, apart from its curved juncture with land 22.

The land 22 extends from the cutting surface 14 to the chip breaker 20. As shown clearly in Figure 3 the land 22 is a declivity 30 (relative to the upper face 16a). As will be appreciated by those skilled in the art, in use, the declivity 30 encourages swarf towards the chip breaker 20.

The protrusion 24 (shown clearly in Figure 7) comprises two sloping faces 32, both of which are directed to make an obtuse angle to the chip breaker 20. The sloping faces 32 are substantially planar and converge together towards the cutting surface 14. The angle made between the converging faces is approximately 305, marked as A in Figure 7; this angle may be varied by plus-or-minus 15-. The sloping faces 32 make an angle of 70 relative to each other, marked B in Figure 5; a variance of plus-or-minus 15 is permissible.

The protrusion 24 additionally comprises a third sloping face 34 at the rear of the protrusion 24 relative to the cutting surface 14.

The sloping face 34 forms a convex curve, joining the two sloping faces 32 to form a generally pointed "tear drop" shaped protrusion 24. The sloping face 34 makes an angle of 107 to the vertical (the 'vertical' in this case is perpendicular to lower face 16b).

The protrusion 24 is spaced from the chip breaker 20. In this embodiment this means that the convex face 34 is spaced from the chip breaker 20.

In operation the insert 12 is mounted in a holder using an anchor (not shown) in the counter-sunk hole 36 shown in Figure 7.

This method of mounting is well-known in the art. Once relative movement has been achieved between a work piece and the insert, the insert and the work piece are brought into contact and the machining begins.

Swarf generated by the cutting action of the insert 12 is directed by the shape of land 22 towards chip breaker 20, in a similar manner to that known in the art. Before reaching the chip breaker 20 a majority of the swarf will impinge against one of the sloping surfaces 32 of the protrusion 24, the swarf will be deflected by this contact. The deflection tends to be substantially in the plane of the insert because of the angular orientation of the sloping faces 32 so the swarf will still normally impinge against the chip breaker. This double action improves the swarf reducing performance of the insert 12.

In general, the faster the swarf comes off the work piece during machining, the greater the advantage to the tool. The "tear drop protrusion 24 (comprising surfaces 32 and 34) accelerates the swarf material coming off the work piece towards the chip breaker 20. The wearing factor on the cutting edge of the tool insert is thereby reduced.

Generally the insert will be formed from a tungsten-carbide alloy using manufacturing techniques well-known to those skilled in the art.

The invention is clearly not restricted to the type of insert described above, although it is believed to be especially useful for this type of application. Other chip breaker constructions can be used, as may other protrusion configurations.

Claims (7)

1. A cutting insert comprising a body having a cutting surface and a chip breaker spaced from the cutting surface by a land characterized in that there is provided a protrusion from the land between the chip breaker and the cutting surface, whereby, in use, swarf originating from the cutting action of the cutting surface is deflected by the protrusion.

2. A cutting insert according to Claim 1 wherein the protrusion comprises a sloping face.

3. A cutting insert according to Claim 2 wherein the sloping face is a face that is neither perpendicular nor re-entrant relative to the land.

4. A cutting insert according to Claim 2 or Claim 3 wherein the sloping face makes an obtuse angle to the chip breaker surface.

5. A cutting insert according to any of the preceding Claims wherein the protrusion comprises two sloping surfaces converging together towards the cutting surface.

6. A cutting insert according to Claim 5 wherein divergent ends of the protrusion surfaces are joined by a convex surface.

7. A cutting insert according to Claim 6 wherein the protrusion forms a general shape of a pointed tear drop in section.