WO1989011367A1

WO1989011367A1 - Cutting tool

Info

Publication number: WO1989011367A1
Application number: PCT/GB1989/000540
Authority: WO
Inventors: Raymond Leonard Simmonds; Douglas Alan Greensall
Original assignee: Raymond Leonard Simmonds; Douglas Alan Greensall
Priority date: 1988-05-19
Filing date: 1989-05-18
Publication date: 1989-11-30
Also published as: GB8811889D0

Abstract

A cutting tool (10) comprising a tool bit (13) having a body (14) provided with a cutting edge (15), a tool holder having a body (12) provided with a tool bit mounting surface (20) and a clamping surface (30) upstanding therefrom, a clamping member (22) having a tool bit engaging portion (36) in engagement with an abutment part of the tool bit body and a load applying means to apply a load to the clamping member to cause the clamping member to move relative to the tool holder body and press the bit (22) against the clamping surface (30) to clamp the bit to the tool holder (11), wherein the tool bit engaging portion and abutment part comprise a plurality of pairs of interengaging formations, one formation of each pair being provided on the bit and the other on the clamping member, the pairs being spaced apart in a direction away from said clamping surface.

Description

Title: "Cutting tool"

Description of Invention

This invention relates to a cutting tool comprising a tool bit having a body provided with a cutting edge, a tool holder having a body provided with a tool bit mounting surface and a clamping surface upstanding therefrom, a clamping member having a tool bit engaging portion in engagement with an abutment part of the tool bit body and a load applying means to apply a load to the clamping member to cause the clamping member to move relative to the tool holder body and press the bit against the clamping surface to clamp the bit to the tool holder.

Such a tool is referred to hereinafter as a cutting tool of the kind specified.

Hitherto the abutment part of the bit body has been of relatively great depth requiring a relatively thick bit to accommodate the abutment part. Consequently, the bit is relatively expensive where the bit is made of inherently expensive material, such as tungsten carbide. Moreover, when the cutting edge is formed by a tool, such as a diamond grinding wheel, which is capable of forming a given length of material before its useful life is exhausted then a greater number of bits can be made in the given length, the smaller the thickness of the bits.

An object of the invention is to provide a cutting tool of the kind specified in which the thickness of the bit is minimised.

According to the invention we provide a cutting tool of the kind specified wherein the tool bit engaging portion and abutment part comprise a plurality of pairs of inter-engaging formations, one formation of each pair being provided on the bit and the other on the clamping member, the pairs being spaced apart in a direction away from said clamping surface.

Preferably there are three pairs of said formations.

Each pair may comprise an upstanding rib on the clamping member in engagement with a co-operating recess in the body of the bit. Each rib may have an operative surface which faces said clamping surface and is not substantially inclined away from said surface.

Each rib may have a reverse surface, which faces away from said clamping surface and is inclined away therefrom.

Each inter-engaging recess may have an operative face which faces away from said clamping surface and may be inclined thereto at, or substantially at, the same angle as the operative face of the inter-engaging rib and may have a reverse face so as to be spaced away from the reverse face of the rib when the operative faces are in engagement.

The inter-engaging formations may have a height of about 0.5 millimetres and may lie in the range 0.25 - 1.5 millimetre and the recess may have a generally similar depth.

The inter-engaging formations may have a height or depth respectively approximately equal to one quarter of the thickness of the bit.

The bit may be two to three millimetres thick.

Each rib may be straight and extend parallel to the clamping surface.

Alternatively, each rib may comprise at least two mutually inclined parts which are also inclined to said clamping surface. For example, each formation may be "V"-shaped, the apex of the "V" pointing towards the abutment surface and the plane of the "V" lying parallel to said mounting surface.

The clamping member may be translationaly. movable relative to an adjacent surface of the holder body which is adjacent to said clamping surface and perpendicular to the mounting surface.

The adjacent surface may have a threaded passage extending inwardly of the tool holder in a direction normal to said surface and there being a screw-threaded member having a screw-threads of opposite hands at opposite ends, one end being engaged in said screw-threaded passage in the holder body and the other being in screw-threaded engagement in a screw-threaded passage in the clamping member so that rotation of the screw-threaded member to cause the clamping member to move translationaly towards the adjacent surface and hence press the tool bit against the clamping surface.

The clamping member may extend in a direction away from said mounting surface and have spaced there along in said direction the tool bit engaging portion, a fulcrum portion for engagement with the tool holder body and a load applying part at which said load applying means applies said load to the clamping member, the load applying part being disposed between said tool engaging portion and said fulcrum portion, whereby said load applying means may apply said load to the clamping member to cause the clamping member to pivot about the fulcrum portion and press the bit against the clamping surface.

The clamping member may be engaged with the mounting surface so as to be interposed between and separate the tool bit and the mounting surface.

Alternatively, the clamping member may be engaged with the mounting surface so as to be interposed between a part of the tool bit and the mounting surface and another part of the tool bit is engaged with the mounting surface.

The clamping member may be mounted in a recess in the tool holder body for movement translationaly and rotatably towards and away from the clamping surface.

The recess may extend across the full width of the part of the tool holder body carrying the bit and the base of the recess providing said mounting surface.

Alternatively, the recess may extend across only a portion of the width of the part of the tool holder body carrying the bit so that the mounting surface is provided partly by the base of the recess and partly by shoulders of the tool holder body on opposite sides of the recess, which shoulders, as well as the clamping member, engage the bit.

An embodiment of the invention is illustrated, by way of example, to the accompanying drawings, wherein:-

FIGURE 1 is a side elevation of a cutting tool embodying the invention,

FIGURE 2 is a plan view of the tool shown in Figure 1 ,

FIGURE 3 is a fragmentary cross-section, to an enlarged scale, on the line Ill-Ill of Figure 2,

FIGURE 4 is a view similar to that of Figure 2 but of a modification, and

FIGURE 5 is a fragmentary front elevation of a further modification.

Referring to the Figures, an edge tool 10 comprises a tool holder 1 1 having a body 12 and a replaceable tool bit 13 having a body 14 with a single cutting edge 15. The body 12 of the tool holder has a generally rectangular cross-section shank 16 but is provided with a desired configuration to enable it to fit into a lathe or other tool with which it is to be used. For example, the shank may be provided with a dovetail cross-section rib by which the shank is adapted to be secured in a tool holder or a lathe in which a work piece "W" is rotated in the direction of the arrow "A" end the tool holder moves the bit 13 into cutting engagement with the workpiece in the direction of the arrow "B".

The tool holder body 12 has a planar mounting surface 20 which is inclined to the longitudinal axis L-L of the tool holder body at an angle of 80°. This angle is equal to the complement of the cutting rake of the surface 15a at the cutting edge 15 since the surfaces 15a and 20 are parallel. The cutting rake may vary depending upon the material to be cut and may lie in the range 50 to 100 , a negative cutting rake being appropriate for certain materials.

The body 12 has a recess 21 in the form of a rebate extending across the full width of the body. The base of the recess provides the mounting surface 20. The recess 21 receives a clamping member 22 which is mounted in the recess 21 on the mounting surface 20 for translational and rotational movement as hereinafter to be described. The clamping member 22 in cross-section as shown in Figure 3 is of generally truncated prism shape having a first surface 23 which lies generally parallel to the plane of the remainder of a side surface 24 of the tool holder which is parallel to the longitudinal axis L-L and a second surface 25 which lies generally parallel to an adjacent surface 26 of the tool holder at the inner end of the recess 21. The surface 23 may be at some other angle, for example, it may be parallel to the surface 25 if it is desired. The surfaces 25 and 26 are respectively perpendicular to a base surface 27 of the clamping member 22 and the mounting surface 20. If desired, the surfaces 27 and 26 may be inclined to the surface 24 at any other suitable angle.

The tool holder has a clamping surface 30 which is parallel to the surface 24 and hence to the longitudinal axis L-L. Again, if it is desired, this angle may be varied as appropriate from that described hereinbefore so long as the desired clamping action, hereinafter to be described is achieved.

The clamping member 22, extends across the full width of the body 12 and, on the surface 25 thereof, is provided with a transversely extending rib 31 which provides a fulcrum 32 which engages the surface 26.

A screw-threaded passage 33 is formed in the holder body normal to the surface 26 and a screw-threaded passage 34 but with a thread of opposite hand to the passage 33 is formed through the clamping member 22. A double ended screw 35 is threadedly engaged with the threads of the passages 33 and 34 and is provided with a hexagon recess 36 at its outer end for engagement by a tool to enable it to be rotated unless to move the clamping member 22 translationally towards or away from the adjacent surface 26 of the tool holder body.

On its upper surface 35, which lies substantially parallel to the plane of the mounting surface 20, the clamping member 22 is provided with a tool bit engaging portion 36 in engagement with an abutment part 37 of the tool bit body 14. The tool bit engaging portion and the abutment part each comprises a plurality of pairs of inter-engaging formations, the pairs being spaced apart in a direction extending away from said clamping surface 30. In the present example there are three pairs of such formations.

Each pair comprises an upstanding rib formation 38a - c on the clamping member 22 in engagement with a co-operating recess 39a - c formed in the body 14 of the bit. Each rib has an operative surface 40a-c which faces said clamping surface 30 and is inclined towards the surface 30 at an included angle B of 20 .The angle B depends upon the angle A between the surface 20 and the axis L-L, the angle C between the surface 40a -c and the base surface 27 of the clamping member 22 and the angle between the clamping surface 30 and the axis L-L. Generally, the angle C may lie in the range 1 ° to 20 , the surface 30 is parallel to the axis L-L and the angle A may lie in the range 50 to 100 .

Hence, the clamping surface is inclined to the mounting surface at an included acute angle of 20 and may lie approximately in the range 50 to 100°.

In any particular case the angles are arranged to achieve a desired clamping action and generally the angle B will lie in the range 1° to 60 and preferably lies in the range 15 to 30 and typically is about 20°. In addition each rib has a reverse surface 41 a - c which faces away from the clamping surface 30 and is inclined away therefrom.

Each inter-engaging recess 39a - c has an operative face 42a - c which faces away from the clamping surface 30 and is inclined thereto at the same angle as the operative face 40a of the inter-engaging rib. In addition each recess has a reverse face 43a - c disposed so as to be spaced a small distance away from the reverse face 41 a - c of the inter-engaging rib when the operative faces thereof 40a - c, 42a - c are engaged. The ribs have a height h of 0.5 millimetres in the present example but may lie approximately in the range 0.25 - 1 millimetre and the recesses have a generally similar but slightly greater depth h 1, the greater depth being virtue of the clearance between the surfaces 41 a - c, 43a - c. In the present example the bit has a thickness t of two millimetres and thus the recesses 39a - c are a depth of approximately one quarter of the thickness of the bit. Of course, if desired, the thickness of the bit and the depth of the recess and height of the ribs may be varied from that described above consistent with achieving a minimum possible bit thickness and adequate retention of the bit.

If desired, a greater or smaller number of inter-engaging ribs and recesses may be provided although it is considered that more than three, or possibly four, pairs of such inter-engaging formations are not required since the clamping loads are primarily taken on the first two to four pairs of interengaging operative surfaces.

In use, the screw 35 is rotated to move the clamping member 22 away from the adjacent surface 26 to permit a bit 13 to be engaged with the ribs thereof. The screw 35 is then rotated in the opposite direction to move the clamping member 22 translationally towards the surface 26 and consequently move the bit 13 into engagement with the clamping surface 30. Continued rotation of the screw 35 then causes the clamping member 22 to rotate about an axis provided by the fulcrum 32 in engagement with the surface 26. This causes the clamping member 22 to tilt, this being permitted by play in the screw threads, so that the tool bit 13 is clamped against the clamping surface 30 with a high degree of security because of lever arm from the fulcrum 32. The inclination of B between the clamping surface 30 and the operative surfaces 40a - c provides a re-entrant shape which further improves the security of retention of the bit.

Although in the above example the ribs are straight and extend parallel to the clamping surface 30 if desired, each rib may comprise at least two mutually inclined parts which are also inclined to the clamping surface. For example, as illustrated in Figure 4, each rib may be "V"-shaped in plan vew with the apex of the "V" pointing towards the clamping surface 30 and the plane of the "V" being parallel to the plane of the mounting surface 20.

If desired, instead of a single tool bit 13 a plurality of tool bits may be clamped to the tool holder by the clamping member by providing a desired number of tool bits each having a plurality of recesses to engage the ribs of the clamping member or such other plurality of formation parts as appropriate to correspond to the formation parts provided on the clamping member in any particular case.

Alternatively, where a single tool bit is provided instead of the tool bit being of the same length as the clamping member it may be of shorter length and located at a desired position transversely thereof. Further alternatively, as shown in Figure 5, the recess may be of less width than the tool holder body 1 12, being a generally channel shaped slot 121 so that in this case the mounting surface 120 is stepped. A lower part 120a of the mounting surface is provided by the base of the slot 121 and is engaged by the clamping member 122 and a pair of upper parts 120b of the mounting surface are provided on opposite sides of the slot and engage the bit 1 13. Ribs 138a - c similar to the above described ribs project above said upper parts 120b of the mounting surface and are received in similar recesses 139a - c in the bit 1 13.

The tool bit may be provided with a cutting edge of any desired configuration to provide a cut of desired shape and the present invention permits easy replacement and inter-change of tool bits of desired configuration.

In the present examples the bit 13 is made of tungsten carbide but may be made of high speed steel or any other suitable material which can be machined or manufactured by a powder metallurgical technique.

Features of any embodiment or embodiments described herein are applicable mutatis mutandis to any other embodiment or embodiments described herein.

The features disclosed in the foregoing description, or the following claims, or the accompanying drawings, expressed in their specific forms or in terms of a means for performing the disclosed function, or a method or process for attaining the disclosed result, or a class or group of substances or compositions, as appropriate, may, separately or any combination of such features, be utilised for realising the invention in diverse forms thereof.

Claims

CLAIMS:

1. A cutting tool comprising a tool bit having a body provided with a cutting edge, a tool holder having a body provided with a tool bit mounting surface and a clamping surface upstanding therefrom, a clamping member having a tool bit engaging portion in engagement with an abutment part of the tool bit body and a load applying means to apply a load to the clamping member to cause the clamping member to move relative to the tool holder body and press the bit against the clamping surface to clamp the bit to the tool holder, wherein the tool bit engaging portion and abutment part comprise a plurality of pairs of inter-engaging formations, one formation of each pair being provided on the bit and the other on the clamping member, the pairs being spaced apart in a direction away from said clamping surface.

2. A tool according to Claim 1 wherein there are three pairs of said formations.

3. A tool according to Claim 1 or Claim 2 wherein each pair comprises an upstanding rib on the clamping member in engagement with a co-operating recess in the body of the bit.

4. A tool according to Claim 3 wherein each rib has an operative surface which faces said clamping surface and is not substantially inclined away from said surface.

5. A tool according to Claim 3 or Claim 4 wherein each rib has a reverse surface, which faces away from said clamping surface and is inclined away therefrom.

6. A tool according to any one of Claims 3 to 5 wherein each interengaging recess has an operative face which faces away from said clamping surface and is inclined thereto at, or substantially at, the same angle as the operative face of the inter-engaging rib.

7. A tool according to any one of Claims 3 to 6 wherein each interengaging recess has a reverse face so as to be spaced away from the reverse face of the rib when the operative faces are in engagement.

8. A tool according to any one of the preceding claims wherein the interengaging formations have a height lying in the range 0.25 - 1.5 millimetre.

9. A tool according to any one of the preceding claims wherein the interengaging formations have a height or depth respectively approximately equal to one quarter of the thickness of the bit.

10. A tool according to any one of the preceding claims wherein the bit is two to three millimetres thick.

1 1. A tool according to any one of the preceding claims wherein each interengaging formation is straight and extends parallel to the clamping surface.

12. A tool according to any one of Claims 1 to 10 wherein each interengaging formation comprises at least two mutually inclined parts which are also inclined to said clamping surface.

13. A tool according to Claim 12 wherein each formation is "V"-shaped, the apex of the "V" pointing towards the abutment surface and the plane of the "V" lying parallel to said mounting surface.

14. A tool according to any one of the preceding claims wherein the clamping member is translationaly movable relative to an adjacent surface of the holder body which is adjacent to said clamping surface and perpendicular to the mounting surface.

15. A tool according to Claim 14 wherein the adjacent surface has a threaded passage extending inwardly of the tool holder in a direction normal to said surface and there being a screw-threaded member having a screw-threads of opposite hands at opposite ends, one end being engaged in said screw-threaded passage in the holder body and the other being in screwthreaded engagement in a screw-threaded passage in the clamping member so that rotation of the screw-threaded member causes the clamping member to move translationaly towards the adjacent surface and hence press the tool bit against the clamping surface.

16. A tool according to any one of the preceding claims wherein the clamping member extends in a direction away from said mounting surface and has spaced there along in said direction, a fulcrum portion for engagement with the tool holder body, a load applying part at which said load applying means applies said load to the clamping member and the tool bit engaging portion whereby said load applying means may apply said load to the clamping member to cause the clamping member to pivot about the fulcrum portion and press the bit against the clamping surface.

17. A tool according to any one of the preceding claims wherein the clamping member is engaged with the mounting surface so as to be interposed between and separate the tool bit and the mounting surface.

18. A tool according to any one of Claims 1 to 16 wherein the clamping member is engaged with the mounting surface so as to be interposed between a part of the tool bit and the mounting surface and another part of the tool bit is engaged with the mounting surface.

19. A tool according to any one of the preceding claims wherein the clamping member is mounted in a recess in the tool holder body for movement translationaly and rotatably towards and away from the clamping surface.

20. A tool according to Claim 19 when dependent upon Claim 17 wherein the recess extends across the full width of the part of the tool holder body carrying the bit and the base of the recess provides said mounting surface.

21. A tool according to Claim 19 when dependent upon Claim 18 wherein the recess extends across only a portion of the width of the part of the tool holder body carrying the bit so that the mounting surface is provided partly by the base of the recess and partly by shoulders of the tool holder body on opposite sides of the recess, which shoulders, as well as the clamping member, engage the bit.

22. A tool substantially as hereinbefore described with reference to Figures 1 to 3, or Figure 4, or Figure 5 of the accompanying drawings.

23. Any novel feature or novel combination of features disclosed herein and/or shown in the accompanying drawings.