GB2037629A - Locating tips or inserts into tools - Google Patents

Abstract

A tipped cutting form, turning or milling tool or tip or tipped insert therefor is provided in which the base or substrate (21) of the or each tip (2) is formed, e.g. with a tongue (22) or facetted projection (230) for indexing so as to have a projection and recess locating engagement with corresponding formation, e.g. a recess (12) in a rebate (10, 130) for the tip (2) in an insert (1, 110) or tool body. Alternatively an insert (68) receiving a tip or tips (2) located and secured therein has a projection (62) and recess locating engagement in a tool body rebate either direct or by a mounting piece. The tips (2) or inserts may be permanently secured (e.g. by brazing) or releasably secured (e.g. by clamping or screwing) in position of use. <IMAGE>

Description

SPECIFICATION Tipped cutting tools and tips and tipped inserts therefor This invention relates to tools for cutting, i.e. turning or similarly machining workpieces wherein the tool is provided with a cutting tip or tips of which at least the actual cutting part is of hard material, e.g.

consisting of or containing diamond or cubic boron nitride.

The invention has particular practical application to such tools and tips or tipped inserts therefor where the tips (also referred to as blanks) are of the kind consisting of a sintered layer of intergrown diamond or cubic boron nitride crystals in a matrix bonded on to a substrate of supporting material such as tungsten carbide. Tips of this kind are available in a wide variety of standard or special shapes under the registered trade marks SYNDITE (de Beers) or COMPAX (General Electric Company of U.S.A.).

The invention includes not only the tipping of tool shanks or the like but in particular the tipping of inserts such as indexible inserts which in use are mounted on a shank, body or holder of a complete tool and the object of this invention is to provide an improved mounting of the cutting tip or tips on the tool or insert whereby accurate tipping can be readily effected whilst other practical and operating advantages obtained and also further developments will be apparent from the following disclosure.

According to this invention a tipped cutting tool or tip or tipped insert therefor is characterised by the base or substrate of the or each tip being formed so as to have a projection and recess locating engagement with corresponding formation in a rebate for the tip in the tool body or insert when secured therein and/or wherein the tipped insert is adapted to have a said projection and recess locating engagement with corresponding formation in a rebate for the insert in the tool body when secured therein.

As will be apparent from the previous paragraph the invention includes tips (or blanks) so formed for said locating engagement in a rebate having a corresponding formation in an insert or in a tool body or shank whilst the invention further includes tipped inserts formed for similar locating engagement with complementary formation in a tool body rebate.

The invention still further includes the resulting method of manufacture of tipped cutting tools, tips and tipped inserts therefor to provide the projection and recess locating engagement.

Referring to the drawings and in practice the tips, inserts and tools and manufacturing procedure are as follows, in which: Figure 1 is a face view of an insert tipped in accordance with this invention, Figure 2 is a detail face view on a somewhat enlarged scale of a corner portion of the insert shown in Figure 1, Figures 3 and 4 are plan and underside plan views respectively of the tip per se, Figure 5 is a rear view of the insert as viewed in the direction of the arrow V of Figure 3, Figure 6 is a detail plan view of a rebate in the face of the insert for receiving a tip, Figure 7 is a side view partly in section showing the tip and insert in detached relationship, i.e. as viewed in the direction of the arrow VII of Figure 1, Figure 8 is a sectional side view similar to Figure 7 showing the tip mounted in the insert, Figure 9 is a plan view of a form tool provided with tips in accordance with the invention, Figure 10 is a sectional side view of a turning tool provided with an indexible arrangement of tip, Figure 7 7 is an underside plan view of the tip, Figure 12 is an underside plan view of a further arrangement of indexible tip, Figure 13 is a detail sectional view showing a recess receiving the tip shown in Figure 12, Figure 14 is a plan view of a further arrangement of tipped cutting tool, Figure 15 is a detail cross section taken on the line XV-XV of Figure 14, Figures 16 and 17 are elevations showing tipped "Microbore" tools.

Figures 18 and 19 are detail plan and side elevation views of a clamped arrangement of a tip on a tool shank, Figures 20 to 23 are views similarto Figures 18 and 19 but showing further locating arrangements, Figure 24 is a perspective view from above of a tipped insert located on a tool shank, Figures 25 to 29 are perspective views from above each showing an alternative form of tipped insert for located mounting on a tool shank, Figures 30 and 31 are similar perspective views of further arrangements of tipped insert for located mounting, and Figure 32 is a perspective view of a screw mounted tipped insert.

Like parts are referred to by the same or similar reference numerals throughout the drawings.

Referring to Figures 1 to 8 and firstly to Figure 1, an indexible cutting tool insert 1 (e.g. as known under the trade names "Sandvik", "Wimet" and "Kennametal") is shown which is preferably of tungsten carbide and is provided with tips 2 received in rebate 10 at each corner of the face of the insert.

The insert may have a similar arrangement of tips on the other face. The insert 1 is shown of square form in face view but may be of other suitable shape such as rhombic form. A central mounting hole is shown provided at 11.

Each tip 2 is of quadrant form in face view and consists of a substrate 21, e.g. of tungsten carbide having a facing or layer 20 consisting of a matrix containing crystals of diamond or other hard or super abrasive material such as cubic boron nitride.

In the case of diamond, crystals of the latter are preferably from a polycrystalline form of diamond such as Carbonados or Ballas forms, (i.e. natural or synthetic).

In accordance with this invention the base or substrate 21 of the tip 2 has a projection and recess locating engagement with the insert 1 and in the example shown in Figures 2 to 8, the underside of the substrate 21 is provided with a tongue 22 which engages a groove 12 formed in the bottom of the rebate 10 in the insert.

The tongue 22 and groove 12 are shown radially directed in relation to the centre of the insert 1 and point of the tip 2 and the tongue 22 and groove 12 are of taper form, i.e. of progressively increasing depth towards the rear of the tip 2 end back of the rebate 10, i.e. from the cutting part of the tip 2.

As will be appreciated the tongue and grooved engagement 22, 12 provides positive location and accurate positioning of the tip 2 in the insert rebate 10 which is of particular advantage in quickly brazing a tip 2 into a rebate 10 so that the diamond crystals are subject to the temperature of the brazing operation for a minimum period (e.g. a few seconds) in the interests of avoiding or minimising thermal degradation of the crystals. Furthermore the accurate positioning obtained is such that a minimum of skill is necessary in carrying out the tip mounting operation.

Any known or suitable brazing or other securing procedure may be employed and together with the flat faces of the underside of the substrate 21 and those of the rebate 10, the tongue 22 and groove 12 provide extended surface areas for high strength brazing purposes. Thus greater contact with silver solder used in brazing of the tips 2 is afforded by the extended surface area and also retention of the solder during brazing by the tongue and groove location 22, 12. Such location further increases the strength of the brazed joint against fracture.

In the case of joining together faces of the same or similar materials such as tungsten carbide to tungsten carbide, the faces to be mated should be pre-coated with a compatible material such as copper, silver or nickel which gives high interface adhesion by low temperature bonding techniques thus avoiding or minimizing thermal damage of the polycrystalline diamond or cubic boron nitride of the tip or blank 2. The main techniques for this purpose can be ion exchange plating and vacuum deposition of metals and compounds by the sputtering or evaporation procedures.The mating faces should be de-greased and thoroughly pre-cleaned, e.g. by high intensity fine grit shot blasting or other suitable processes especially where it is necessary to remove thermal damage due to the use of electrical discharge machining (as referred to below) to provide sound mating surfaces priortotheirfinal preparation. Such preparation may be effected by a suitable sputtering technique in providing the pre-coating of copper, silver, nickel or other compatible material.

In the case where the tungsten carbide substrate 21 of the tip or blank 2 is brazed to a dissimilar material such as mild steel, an intermediate expansion joint between the mating faces is required to lessen the risk of metal fatigue failure of the joint.

The most suitable method which may be employed is that using an intermediate material for the purpose, such as silver solder faced copper sheet or mesh such as those known under the trade names "trefoil" and "Easyflow" (Johnson Matthey Metals Limited.

The formation of the tip substrate 21 and the insert rebate 10 to provide the tongue 22 and groove 12 may be effected in any suitable manner such as when sintering the substrate 21 and insert 1, i.e.

when the material is in the "green" stage or by machine, e.g. grinding. Techniques for forming the substrate 21 and insert 1 can include spark erosion, i.e. electrical discharge machining or electrochemical machining or ultrasonic machining or cutting by means of a laser beam.

Whereas the arrangement described is preferred, if desired, a tongue or other projection of the insert rebate 10 may engage a groove or recess in the underside of the tip substrate 21.

Although after brazing the tip 2 is firmly secured to the insert 1, a further advantage of the invention resides in the fact that under operating conditions the tip 2 is positively located against cutting forces whilst the cutting load on the tip 2 tends to thrust the inclined tongue 22 and groove 12 further into engagement. Furthermore the abutment of the rear ofthetongue 22 against the back face of the rebate 10 constrains the tip 2 against rocking or lifting movement out of the rebate 10. The junction of the tongue 22 to the substrate 21 is preferably radiussed as at R in Figure Sin order to minimise the likelihood of fracture.

Referring to Figure 9 an example of a form tool is shown having three cutting tips 2 of sector or "pie slice" form each secured on the tool body 100 and located thereon by the tongue and groove engage ment 12.

In Figures 10 and 11 an alternative embodiment of the invention is shown in which the tip 2 which again consists of a substrate 211 having a matrix layer 201 containing diamond or similar crystals, is retained in a recess 120 in the tool body 110, by a clamp 3.

For obtaining locating engagement of the tip 2 with the recess 120, a projection 221 on the underside of the substrate 211 is faceted, the facets 23 of which engage or seat against corresponding facets 13 in the recess 120. In the example shown, the projection 221 and recess 120 each have four facets, 23,13 respectively to enable the tip 2 to be indexed four times through 90 in which case the upper part of the substrate 211 and the matrix layer 201 are preferably of circularform in plan as shown, but may be of square or other suitable configuration.

The number of facets on the projection and recess may be considerably increased in order to obtain correspondingly greater number of positions to which the tip 2 may be indexed. Thus, as shown in Figures 12 and 13, sixteen facets 230, 130 are provided, the substrate 212 and in particular the matrix layer 202 being of corresponding regular polygonal form.

Referring to Figures 14 and 15 a turning tool is shown in which an elongate tip 2 is received by a rebate 101 in the tool body 111, the substrate 213 of the tip being of increasing depth towards the back of the rebate 101, whilst the base 112 of the rebate is of correspondingly inclined form. This again provides positive projection and recess location of the tip 2 on the tool body 111 and also withstands cutting loads in the manner already described with reference to Figures 2 to 8.

In all the examples herein described, the substrate and insert or tool body or that part of the tool body in the vicinity of the tip are preferably of tungsten carbide which has the advantage of having a coefficient of expansion closely similar to that of diamond or cubic boron nitride.

It will also be appreciated that tipped cutting tools and inserts are capable of practical application to a wide variety of cutting tools such as turning tools, form tools and multi-teeth cutters, the latter including routing and milling cutters.

Owing to the brittle nature of the tip 2, the procedure of tapping the tool into position during setting up should not be adopted so as to avoid fracture of the tip. To prevent such practice the tool should be adjusted by fine adjustment screw or other suitable means such as that provided by "Microbore" tool units as manufactured by Alfred Herbert Limited.

Such a unit is shown in Figure 16 in which the cutting tool 14 receives a tip 2 of substantially half moon shape located in a rebate 140 by tongue and groove engagement which is indicated at 22, 12. The tip 2 may be initially of half moon shape, a projecting portion beyond the end of the tool 14 being ground away after brazing the tip in position and so that it assumes the shape shown. Thus by turning the adjusting nut 142, the threaded holder or cartridge 141 carrying the cutting tool 14 can be advanced or retracted axially, and then locked in position by tightening a lock screw 143. The complete tool unit is shown mounted in a holder bar 4.

An alternative form of tip 2 in such a tool is shown in Figure 17 again with tongue and groove location 22,12 and in which subsequent grinding ofthetip after brazing in position is kept to a minimum.

Referring to Figures 18 and 19 a quadrant shaped tip 2 similar to that shown in figures 1 to 8 is shown directly clamped at 30 in a rebate 401 in a tool body or shank 400 and has a tongue and recess location 22,412 with the latter. The arrangement is shown applied to a sharply pointed tool with the tip 2 overhanging the tool shank 400. The tool shank may be of mild steel and the releasable clamping at 30 of the tip 2 enables it to be removed for sharpening which is convenient where the tip has to be returned for such attention. Clamping of the insert 2 also avoids the possibility of thermal damage to the diamond crystals of the matrix layer 20. The arrangement is suitable for light duty use, e.g. in machining plastic materials.

Further arrangements of projection and recess locating engagement of a tip 2, i.e. directly on a tool body or shank are shown in Figures 20 to 23 wherein Figures 20 and 21 a projection in the form of a pin or stud 515 in the rebate 501 of the tool shank 500 engages in a recess or hole 25 in the underside of the substrate 21 of the tip 2. In this instance the hole 25 may be formed by spark erosion and the stud 515 built up by a similar electrical discharge spark technique. Alternatively a hardened pin inserted in a bore in the rebate 501 may provide the projection 515 or a projection may be provided on the underside of the substrate 21 for engagement with a hole in the rebate 501.

In figures 22 and 23 a projection 516 shown of part circular form is provided at the back wall of the rebate 502 in the tool body and engages a complementary recess 26 in the rear end of the substrate 21 of the tip 2 in order to provide the locating engagement of the tip 2 on the tool shank 500. Here again the projection 516 and recess may be formed by spark erosion or spark build up. Particularly in the case of a smalll size of the tool shown in Figures 22 and 23 the projection 516 re-inforces the seat 502 of the at its junction with the shank 500.

The tips 2 shown in Figures 20 to 23 may be brazed or clamped in position of use.

Particularly for heavy duty use and in the development of the invention shown in figure 24 an insert or slab 60 of tungsten carbide has a tongue and groove or recess locating engagement 62,612 in a correspondingly formed rebate 601 of the tool body or shank 600, the insert 60 being brazed in the rebate 601.

The insert 60 itself receives a tip 2 preferably also in accordance with this invention, e.g. having a tongue and recess locating engagement 22,12 in the rebate 601. Since cutting is effected by the tip 2 and not by the body of the insert 60, the latter can be of tougher and less brittle tungsten carbide, i.e. of non-cutting quality so as to be more shock resistant to cutting stresses.

Various forms of such inserts adapted to have an appropriately directed tongue and groove engagement in the tool body rebate 601 for projection and recess locating engagement therein as shown at 61 and 66 to 69 in Figures 25 to 29 respectively and in which the body of the insert 61 or 66 to 69 receives one or more tips 2 brazed in rebates therein preferably with locating engagement 22, 12 as described above. In some cases, e.g. in Figure 25 the square insert 61 may receive tips 2 at diagonally opposite corners so that the insert can be changed round to present an alternative tip 2 at the cutting position. In such a case the tipped insert is releasably clamped or screw mounted in a suitable tool body rebate 601, whilst in all cases the tips 2 can be repeatedly sharpened by grinding, i.e. until the tip 2 is virtually used up.

Referring to Figures 30 and 31 and in order to enable inserts of standardized form to be used the insert 70 can be secured such as by brazing 78 (Figure 30) to a mounting piece 80, e.g. of mild steel which, in turn, has a tongue 82 for locating engagement with a corresponding groove or recess in an appropriate tool body rebate 601. In Figure 31 a standard form of insert 71 is secured by a central screw 73 to a mounting piece 81 so that the insert can be released and indexed to present a fresh tip 2 at the cutting position. Here again the projection and recess locating engagement of the invention is preferably utilized for the location of the or each tip 2 on the insert 70 or 71 as indicated at 22, 12. Thus standardised inserts hitherto used on a throw away basis can be given a longer serviceable life, e.g. for general machining use and can often be re-ground.

This is advantageous where the cutting material of the tip 2 is diamond or cubic boron nitride.

In Figure 32 an insert 90 having a tip 2 located thereon by tongue and recess and engagement 22, 12 is shown secured in a rebate 901 therefor of a tool shank 900 by a screw 93. Thus the insert 90 can be readily removed for separate re-grinding.

Claims (12)

1. Atipped cutting tool or tip or tipped insert therefor characterised by the base or substrate of the or each tip being formed so as to have a projection and recess locating engagement with corresponding formation in a rebate for the tip in the tool body or insert when secured therein and/or wherein the tipped insert is adapted to have a said projection and recess locating engagement with corresponding formation in a rebate for the insert in the tool body when secured therein.

2. Atipped cutting tool ortip or tipped insert therefor according to claim 1 wherein the projection and recess locating engagement is provided by a tongue and recess or groove engagement.

3. Atipped cutting tool ortip ortippedinsert therefor according to claim 2 wherein the tongue and recess or groove locating engagement is of increasing depth in a direction away from the cutting part of the tip or tipped insert.

4. Atipped cutting or tool or tip or tipped insert therefor according to claim 1 wherein the projection and recess locating engagemnt is faceted to provide indexible locating engagement.

5. Atipped cutting tool or tip or tipped insert therefor according to claim 1 wherein the projection and recess locating engagement is provided by an inclined formation of increasing depth engaging a corresponding inclined recess.

6. A tipped cutting tool or tip or tipped insert therefor according to claim 1 wherein the projection and recess locating engagement is provided by a stud, pin or like member or formation engaging a recess or hole therefor.

7. Atipped cutting tool or tipped insert therefor according to any of the preceding claims wherein the tipped insert is secured to a mounting piece adapted to have a projection and recess locating engagement in a rebate therefor in the tool body when secured therein.

8. Atipped cutting tool or tipped insert therefor according to claim 7 wherein the insert is permanently secured, e.g. by brazing to the mounting piece or is detachably or indexibly secured thereon, e.g.

by screw means.

9. A tipped cutting tool or tip or tipped insert therefor according to any of the preceding claims wherein the base or substrate of the tip and/or the insert is of tungsten carbide.

10. A tipped cutting tool or tip or tipped insert therefor arranged to have a projection and recess locating engagement substantially as herein described with reference to any of the embodiments thereof shown in the accompanying drawings.

11. Method of manufacture of a tipped cutting tool or tip or tipped insert therefor according to any of the preceding claims wherein the method consists of forming the tip and insert and/or the tool body for said projection and recess locating engagement.

12. Method of manufacture of a tipped cutting tool or tip or tipped insert therefor according to any of claims 1 to 10 wherein the or each method is substantially as herein described with reference to the accompanying drawings.