GB2082501A - Location of a cutter in a cutter head and a jig for supporting the cutter during grinding and regrinding - Google Patents

Abstract

A cutter 14 is secured in the cutter head with locating edges 50, 52 abutting fixed stops 36, 38. In the regrinding of the cutter the location edges are reformed to maintain a predetermined distance H between the cutting edge and the location edges. A jig rotatable through 180 DEG comprises a plate 200 provided with a pair of fences 214, 218 for supporting the cutter during grinding of the cutting edge in accordance with the profile of a template 120 and a cut-out 226 over which the blade is positioned during formation of the location edge. To determine the position of the location edge, a template is used to define the position of a fence 240 relative to a hole 228, the cutter is secured over the cut-out with the profiled edge against the fence 240 and the jig is rotated through 180 DEG so that a stylus 252 fixed to the grinding machine engages a template 232 fixed to the jig. <IMAGE>

Description

SPECIFICATION Method of locating a cutter in a cutter head and apparatus therefor The present invention has been conceived in relation to woodworking machinery such as timber moulding machines, timber shaping machines and spindle moulders, and is concerned with a method of locating a cutter in a cutter head of such a machine. It is to be understood however, that the invention is not restricted to any particular type of machine, and although it will probably find its major application in relation to woodworking machinery, it could be used in any type of machine tool, wherein cutters are located in rotatable cutting heads.

One of the problems associated with the use of rotary cutting heads in woodworking machinery, is that of ensuring that the cutting edges of the cutters always occupy the same radial relationship to the axis of rotation of the cutter head. In the case of a round moulding head, wherein there will frequently be four cutters, it is quite a time consuming and skilled operation to ensure that all four cutters have their cutting edges at the correct location, and if this is not achieved, then the machine will not operate correctly. The setting of the cutters in the moulding head, is particularly difficult, when the cutters themselves have profiled cutting edges.

A similar problem, arises with the two cutters usually fitted between slotted collars of the type used on shaping machines and spindle moulders.

Apart from the necessity to ensure that two or more cutters in the one cutter head have the same radial relationship to the axis of rotation, problems also arise, when the cutters are removed from the cutter head, and regound. At each regrinding operation, it is necessary to carry out a resetting process of the cutters in the cutter head, and this is commonly done on a trial and error basis.

The primary object of the present invention is to provide a method of locating cutters in a cutter head for use in a machine tool, which greatly simplifies the correct location of the cutters, and hence renders the fitting operation less skilled than heretofore.

According to a first aspect of the invention, a method of locating a cutter in a cutter head for use in a machine tool comprises the steps of: forming a cutting edge on the cutter; forming a location edge on the cutter having a predetermined spatial relationship to the cutting edge; and securing the cutter in the cutter head with the locating edge abutting a stop which occupies a fixed position on the cutter head. Since the stop has a fixed relationship to the cutter head, and since the location edges on two or more cutters have the same determined spatial relationship to the cutting edges of those cutters, it follows, that both or all the cutters, will automatically have their cutting edges in the same spatial relationship to the cutter head.

A preferred method comprises the further step of: removing the cutter from the cutter head; reforming the cutting edge on the cutter; reforming the location edge on the cutter to maintain the determined spatial relationship between the cutting edge and the location edge and then resecuring the cutter in the cutter head with the location edge abutting the stop, whereby the relationship of the cutting edge to the cutter head remains the same despite reforming of the cutting edge. It will be appreciated, that with this preferred method, it is possible to regrind the cutter, and still ensure that its cutting edge occupies the correct position on the cutter head, when the cutter is replaced on that head.

According to another preferred feature of the invention two or more cutters are located in a rotatable cutter head by employing the method of the first aspect of the invention for each cutter, so that both or all the cutting edges have the same spatial relationship to the rotational axis of the cutter head.

According to another aspect of the invention, a cutter head for use in a machine tool has two or more cutters, each having the same cutting profile formed thereon, each cutter having a locating edge engaging with a respective stop, which stops occupy fixed positions on the cutter head, the arrangement providing that both or all the cutting profiles occupy the same spatial relationship to the axis of rotation of the cutter head. Preferably, there are two or more laterally spaced stops engaging with laterally spaced locating edges whereby rocking of the cutter is prevented.

According to a third aspect of the invention, a method of grinding a cutting edge and a location edge on a cutter for use in a cutter head of a machine tool to ensure that the spatial relationship between the cutting edge and the location edge is repeatable, comprises the steps of: grinding a cutting edge on the cutter; establishing a temporary datum position on a jig having a determined spatial relationship to the jig by means of a remova ble stop; engaging one edge of a template with the removable stop; engaging a first fence with an opposite edge of the template to establish a determined distance between the temporary datum position and the first fence; removing the stop and the template; engaging the cutting edge of a cutter with the first fence; engaging a second fence with the edge of the cutter opposite to the cutting edge; securing the cutter to the jig; presenting the jig to a grinding machine with a notched template forming part of the jig or a member secured to the jig engaging with a stylus occupying a predetermined fixed position relatively to the effective edge of the grinding wheel on the machine, and moving the jig so that the notch template slides over and in engagement with the stylus and the shape of the notch is ground by the grinding wheel into the cutter, to produce a locating edge on the cutter which has a re!ationship to the cutting edge thereon determined by the relationship between the datum position and notch on the jig.The method preferably further comprises the steps of: regrinding the cutting edge of the cutter; relocating the cutter on the jig with its cutting edge in engagement with the first fence on the jig; adjusting the second fence to engage it with the said opposite edge of the cutter; clamping the cutter to the jig and re-presenting the jig to the grinding machine to regrind the notch to produce a fresh location on the cutter having the same relationship to the cutting edge as that obtained at the previous presentation of the jig to the grinding machine.

According to a further aspect of the invention, a jig for grinding a cutting edge on a rectangular plate-like cutter having a cutting edge and a side edge at right angles to the cutting edge comprises a plate carried on an axle mounting and having on its obverse side primary fence means for locating a cutter with its cutting edge parallel with the axis of the axle mounting, and secondary fence means for locating a cutter with its locating side edge inclined with respect to the axis of the axle mounting, the plate having a cut-away portion opening to one edge of the jig plate and positioned so that it coincides with part of a cutter engaging with the secondary fence means and a notched template part projecting from the edge of the jig plate which has the cut-away.In the preferred arrangement the notched template is adjustable on the jig plate in a direction parallel with the cutting edge of a cutter engaging with the secondary fence means.

The invention in all its aspects will be better understood from the following description, which is given by way of example only, with reference to the accompanying drawings, in which: Figure 1 is an elevation partly in section of a round moulding head, Figure 2 is a perspective view of a cutter and a co-operating clamp for use in the moulding head illustrated in Fig. 1, Figure 3 is a perspective view of a slotted collar for a shaping machine, with a single cutter shown in position thereon, Figure 4 is a section on the line IV-IV in Fig. 3, Figure 5 is a plan view of a template, Figure 6 is a perspective view of a cutter grinding machine, Figure 7 is a plan view of a jig, shown in position on the grinding machine ready to grind the profile edge of a cutter, Figure 8 is an end view in the direction of arrow VIII in Fig. 7, Figure 9 is a diagram illustrating a method of lateral setting, Figure 10 is a diagram illustrating a first stage in the grinding of a location edge in a cutter, Figure 11 is a diagram similar to Fig. 10, but showing a second stage, and Figure 12 is a diagram showing a final stage in the grinding of a location edge.

Fig. 1 illustrates a round moulding head 10. which is generally of a type conventionally used in a timber moulding machine, though somewhat modified for the purpose of the present invention.

Basically, the moulding head 10 comprises a steel block which is formed with a series of four cutter mounting positions indicated at A, B, C and D. The moulding head is formed with a bore 12 and is adapted to be fitted on a spindle in the timber moulding machine, so that in operation it is rotated in the direction of the arrow R. Generally, four cutters such as that shown at 14 at the location A will be fitted into the moulding head 10, each cutter projecting tangentially to an imaginary circle drawn about the axis of rotation as illustrated at the location A, whereby, the cutters are successively brought into engagement with a timber workpiece (not shown). In Fig. 1, only the arrangement at the location A has been illustrated in detail, since as will be appreciated, this arrangement is duplicated at each of the locations B, C and D.

At each of these cutter locations, the moulding head 10 is formed with a cut-out providing a relatively deep recess 16 having a locating face 18 tangential to an imaginary circle drawn about the axis of rotation and location faces 20 and 22 parallel with the face 18 there being a step 21 between the deep recess 16 and the face 22. A pair of light helical compression springs 24 is located in a pair of holes 26 formed in the moulding head 10 at the bottom of each deep recess.

Each of the cutters 14 takes the form of a plate-like member (see Fig. 2) made for example of high speed steel, and with a cutting profile 28 ground into its outer edge. The precise shape of the cutting profile will be determined by the profile which it is intended to form in the timber workpiece, and it will be appreciated, that this profile will vary according to the object which is to be manufactured on the moulding machine. However, in the usual arrangement, the profile formed on all four cutters 14 in the moulding head 10 is the same, so that each cutter is adapted to form the same profile in the workpiece. Sometimes however, the moulding head is required to form two separate profiles in the workpiece, and in that case, the cutters 14 at the locations A and C would have the same profile, and the cutters at the locations B and D would have a second profile.

The inner end of each cutter 14 is pressed down into the deep groove of the cut-out in which the cutter is fitted, and in doing so, it compresses the two springs 24. This means, that the springs 24 are always urging the cutter outwardly with respect to the moulding head. For the purpose of securing and locating the cutter 14 in the moulding head, a pair of notches 30 and 32 is formed in opposite lateral edges of the cutter (see especially Fig.

2) and a clamp 34 is associated with each cutter, each of the clamps comprising a metal block having projections 36 and 38 adapted to engage respectively in the notches 30 and 32 of the cutter. The arrangement at each of the four locations on the moulding head is completed by a wedge 40, which also takes the form of a metal block, and a pair of setscrews 42. The wedge has a surface which is adapted to engage with the face 22 formed in the moulding head, and a tapered face 44 adapted to mate with a corresponding tapered face 46 on the clamp 34. Two screw-threaded holes 48 are formed in each of the four cutouts of the moulding head, to receive the two screws 42 apertaining to the wedge 40 at that location on the moulding head.

When fitting a cutter 14 to the moulding head, the cutter itself is first placed in the cutout, with its rear face abutting the face 16.

The projections 36 and 38 of the clamp 34 are then engaged in the notches 30 and 32 of the cutter and then the wedge 40 is engaged between the face 22 and the face 46 on the clamp 34. The whole assembly of cutter, clamp and wedge is then pressed inwardly, compressing the springs 26 engaging the bottom of the clamp 34 on the step 21, and the screws 42 are fitted and tightened. As a result, the cutter 14, clamp 34 and wedge 40, become rigid with the moulding head 10, and the springs 26 are compressed. It is to be noted, that since the cutters 14 are all of the same thickness, the radial position of the clamp 34 and the wedge 40 will always be the same, when the assembly is locked to the moulding head.Since the bottom edges 50 and 52 of the notches 30 and 32 are pressed into engagement with the undersides of the projections 36 and 38, and the radial location of these projections is determined by the position of the step 21, this means that the location of the bottom edges of the profile notches in the cutter 14 relatively to the rotational axis of the moulding head 10 will always be the same. It is known to provide springs urging the cutter 14 outwardly, and it is also known to provide a lug or lugs on the clamp or on the moulding head itself, for insertion into a hole or notches in the cutter, for the purpose of preventing the cutter being dislodged from the moulding head, due to the action of centrifugal force, when the moulding head is rotating at high speed.However, in the known arrangement, the hole or notches in the cutter are only roughly formed, to provide a good clearance around the lug or lugs since there is no question of utilising these lugs for the purpose of determining the radial location of the cutter. In other words, the lug does not engage with the cutter, but only acts as a safety device, if the cutter tends to move outwardly under the action of centrifugal force. In the arrangement in accordance with the present invention however, the bottom edges 50 and 52 of the notches 30 and 32 in the cutter have to be accurately formed, since they play an important part in securing the consistent location of the cutting edges of the cutters with respect to the axis of rotation of the moulding head.The two projections 36 and 38 are laterally spaced relatively to the cutter and since they engage with laterally spaced location edges 50 and 52, they prevent rocking or tilting of the cutter. In addition of course, the projections serve to prevent accidental release of the cutter from the head 10 under the action of centrifugal force.

As will be hereinafter described, the distance H between the location edges 50 and 52 in the cutter 14 and the deepest part of the profile formed on the cutting edge of the cutter is maintained at a constant determined value. Providing this is done, it will be appreciated, that since the location edges 50 and 52 always occupy the same radial position on the moulding head, when the cutters have been clamped in the locations A, B, C and D, this provides an automatic means of ensuring that the radial location of the cutting edges 28 with respect to the axis of rotation is the same. Conventionally, the fitting of the cutters in the moulding head, in order to ensure that they are all at the same radial location on the cutter head is a time consuming and skilled operation because it has to be performed by a system of trial and error.However, given that the distance H is maintained the same on all the cutters (or on both the cutters of the same type, if two different profiles are being formed by the one moulding head) the operation of fitting the cutters 14 in the moulding head is greatly simplified and correct location of the cutting edges is ensured.

It is to be noted that the notches 30 and 32 are wide enough to permit some lateral adjustment of the cutter relatively to the projections 36 and 38. The lateral position of the wedge 44 is determined by the location of its fixing screws 42 and the clamp and wedge are keyed to maintain their lateral position with respect to each other. These two elements are of the same width as the moulding head 10, and consequently their flanks lie flush with the flanks of the head.

Fig. 3 illustrates an arrangement which is generally of a known type, used on shaping machines and spindle moulders. A pair of slotted collars 60 (only one of which is illustrated) is provided, and two profile edged cutters 62 (only one of which is illustrated) are clamped between the collars 60. Each collar is formed with a bore 64 and is adapted to be fitted on to a vertical spindle of the machine, and to be rotated by the spindle in the direction of the arrow S in Fig. 3,. A pair of parallel slots 66 and 68 is formed in each collar 60, these slots extending parallel with a diameter of the collar, and each being wide enough to accommodate the thickness of a cutter such as that shown at 62. The profile edge 70 formed on the cutter 62 projects radially and outwardly from the collar.It will be appreciated, that the cutter which is fitted into the slot 66 has its profile edge pointing on the opposite direction to the illustrated cutter 62, so that the two cutters both face in the direction of rotation of the collars. The collars are connected together by a pair of studs (not shown) which fit into screwed holes 72 and 74, the studs drawing the collars towards each other, to clamp the cutters temporarily whilst the assembly is fitted on to the machine spindle. Once it is on the spindle, a spindle nut is fitted to ensure that the cutters 62 are clamped between the collars 60.

For the purpose of ensuring that the cutters 62 cannot slide out of the collars under the action of centrifugal force, a pair of pins 76 and 78 is provided in each collar, there being one such pin in each of the grooves 66 and 68. Each cutter 62 is formed with notches 79 and 80 somewhat similar to the notches 30 and 32 formed in the cutter 14, and when the cutters are in position, the parts of the pins 76 which project into their respective grooves are located within the notches 78.

However, in the conventional arrangement, these notches 78 play no part in the location of the cutters. In the present arrangement however, the bottom edges 82 of the notches are intended to engage with the pins 76 and 78 as illustrated in Fig. 4. The cutters can be formed with second notches as indicated at 80 but generally the second notch is not required.

Again therefore, providing the distance H between the deepest part of the ground profile on the cutting edge of the cutter and the bottom surfaces 82 is maintained at a constant value, it can automatically be ensured, that the cutting edges have the same radial relationship to the axis of rotation of the collars 60, by pressing the edges 81 into engagement with the pins 76 and 78. As was the case with the arrangement described with reference to Figs. 1 and 2 therefore, it will be appreciated, that the correct location of the cutters 62 in the collars 60 is a relatively unskilled operation, as compared with the previously employed trial and error method.

Now with both the arrangements which have been described above, it is an essential feature, that the distance H on the cutter is maintained at a constant value. X his applies, whether one is considering a plurality of identical cutters to be mounted in a single cutter head (moulding head 10 or collars 60) or whether one is considering the re-grinding of cutters removed from a cutter head. Obviously, at a re-grinding operation, it is necessary to re-grind the location edges 50 and 52 or 82, in order to ensure that the distance H is maintained at the correct value. Apparatus for grinding the location edges in the cutters, and the method of operation will now be further described.

In the first place, a template 90 is provided, and this simply takes the form of a flat rectangular plate of metal, machined along one end edge to produce a profile 92. A notch 92 is formed at the profile end of the template so that the distance W is equal to the width of the cutter 14 or 62. The template is machined at the opposite end to the profile, so that a portion 94 is formed having a width equal to the determined dimension H previously referred to. The profile 92 will of course vary with the profile which is required to be produced on the cutters.

Part of a grinding machine on which the cutters 14 or 16 are ground, is illustrated in Fig. 6. Although only certain parts of the machine are shown in this drawing, this is adequate for an understanding of the present invention, without the description of unnecessary detail. The machine has a grinding wheel mounting, which includes the usual spindle (not visible in the drawings) and grinding wheel adapters. The grinding wheel itself is shown at 100 and the customary grinding wheel guard is shown at 112. It will be appreciated that the machine is equipped with an electric motor and belt drive (not shown) for the grinding wheel.

Part of the machine bed is shown at 114, and a "floating" table 116 is provided, which is free to move within limits both axially and radially with respect to the spindle axis (i.e.

the directions indicated by the arrows L and T in Fig. 6). It is important that the table mounting arrangement is such that the table is quite free to move in the directions indicated, so that it can also make movements which are compounds of the two indicated freedoms. The table is not required to move vertically.

A clamp 118 is provided on the table 116 and a metal template 120 can be secured to the table 116 by the clamp 118, with a profile edge 122 of the template facing the grinding wheel spindle. It will be appreciated, that the template 90 illustrated in Fig. 5 can be fitted in the position shown at 120 in Fig.

6. A fence 121 is provided on the table 116, and this is used as an edge location for a template, as will be hereinafter described.

The machine has a cutter stylus 124 carried bv an adjustable stylus bracket 125, which allows the position of the stylus relatively to the grinding wheel spindle to be preselected.

The stylus mounting arrangement is the subject of Patent Application No: 8026289.

It will be appreciated that it is possible to manipulate the table 116 to bring the profile edge 122 of the template into engagement with the stylus 124, and if one end of the profile edge is so engaged and then the table moved axially (direction of the arrow L) whilst maintaining pressure on the table towards the grinding wheel spindle (direction of the arrow T) the compound path of movement of the table relatively to the grinding wheel 110 is a reversed trace of the profile edge 122.

A support bracket 126 on the table 116 includes a journal mounting 128 for a cutter support shaft 130 which is thus rotatable about its longitudinal axis, parallel with the axis of the grinding wheel spindle. At the right hand end (from the point of view of the operative) the shaft 120 is fitted with a hand wheel 132 and at its left hand end it is fitted with a block 134. The latter is a metal block of quadrilateral cross-section and each of its faces, is adapted to provide support for a cutter blank, one of which is indicated at 144, and a releaseable clamp plate 146 is provided which can be secured to any one of the four operative faces to clamp a cutter blank to the block 134 as shown.This block 134 can be used for grinding cutters which are not required to locate in the manner described with reference to Figs. 1 to 4, and the block 134 can be removed and replaced by a jig, which will be hereinafter described.

The bracket 126 is formed with slots 127 extending forwardly and rearwardly and there are locking screws 129 passing through these slots into the table 116. This arrangement provides a means whereby the position of the shaft 130 and the block 134 or the jig carried thereon, can be adjusted relatively to the table 116.

Finally, the machine is equipped with a cutter guide plate 148 secured to a column 150 on the machine, the top edge of the guide plate 148 providing a location edge for supporting the rear portion of a cutter when the table 116 is moved rearwardly to bring the cutter 144 towards the grinding wheel 100. The column 50 also serves to support a diamond trimmer device for the grinding wheel periphery, which is described in detail in the Specification of Patent Application No: 8026290, but when the guide plate 148 is being used, the column 150 is stationary.

A significant feature of the machine, is that there is provision for feeding the grinding wheel forwardly (i.e. towards the table 116) and that the diamond trimmer for the periphery of the wheel is at a fixed location on the machine. Consequently, each time the wheel is trimmed, its periphery is formed in the same location on the machine. Hence, it is a simple matter to maintain a predetermined spatial relationship between the cutter stylus 124, and the periphery of the grinding wheel 100, where the latter is engaged by a cutter carried by the block 134, or by a jig replacing the block 1 34.

A jig which has been devised specially for the grinding of cutters with a profile and with a locating edge or edges as previously described, is illustrated in Figs. 7 and 8 of the drawings. Essentially, the jig comprises a plate-like element 200, having an obverse face 202 and a reverse face 204. A boss 206 depends from the reverse face of the element 200, and a bore 208 formed in this boss is a close fit on the cutter support shaft 130 of the grinding machine. Thus, when the block 134 is removed from the shaft 130, it is possible to fit the jig on to the shaft 130, and the jig then becomes rotatable about the axis of the shaft 130. in the same manner as the block 134. The jig, in fact, provides an alternative to the block 134, for the purpose of supporting cutter blanks.

The shape of the plate 200, is illustrated in Fig. 7, and it will be observed that there is a rearwardly projecting central portion 210 with a rearwardly facing edge 212, and the arrangement of the bore 208 is such, that when the jig is in position on the grinding machine, with the obverse face 202 uppermost (as shown in Fig. 8), then the rearwardly facing edge 212 is parallel with the spindle axis of the grinding wheel 100. A fixed fence 214 projects upwardly along a locating edge of the central portion 210 of the jig, as shown in Fig. 7, and this fence 214, provides an axial location for a cutter blank 216, illustrated in Figs. 7 and 8.A movable fence 218 is also provided on the central portion 210 of the jig, this fence extending at right angles to the fixed fence 214, and providing a location for the front end of the cutter blank 216-that is the opposite end to the end which faces the grinding wheel 100. Hence. by placing a cutter blank 216 against the staionary fence 214, and then manipulating the cutter blank and the fence 218, it is possible to provide complete location for the cutter blank in both the longitudinal and forward and rearward directions, illustrated respectively in Fig. 7 by the arrows L and T. (These directions are the same as the longitudinal and forward and rearward directions referred to with respect to Fig. 6 of the drawings.) The central portion of the jig is completed by a clamp 220 of conventional construction, whereby the blank 216 can be secured to the obverse face 202 of the plate 200, when the blank has been correctly located. As is evident from Figs. 7 and 8, the blank is normally positioned, with its rearward marginal portion overlying the rear edge 212 of the central portion of the jig.

At the left hand end of the jig, as seen in Fig. 7, the plate-like element 200 is stepped back at 222, so that when the jig is in position on the machine over the floating table 1 16, it is possible to gain access to the clamp 11 8, whereby the template 120 is secured to the top surface of the table 116.

As shown in Fig. 7, the template 120 is in practice located against the stationary fence 121, when it is in the secured position, and its profiled edge projects to the rear of the table 116.

The front edge 224 of the plate-like element 220 is inclined with respect to the rear edge 212 for a purpose which will hereinafter appear. A cut-out 226 is formed in the rear marginal portion of the element 200, and there is a location hole 228 close to the cutout 226, and a pair of fixing holes 230 by means of which a notched template 232 (see Figs. 10 and 12) can be secured to the reverse side 204 of the element 200. As shown in Figs. 10 and 12, the notched template 232 can be adjusted forwardly and rearwardly on the element 200, though generally it remains in a fixed position. In this position, it projects forwardly when the jig is in the position shown in Figs. 7 and 8, and it is formed in its forward end with a notch 234, one edge 236 of which is perpendicular to the front edge 224 of the element 200.

A peg 238 is provided for fitting into the location hole 228, and this peg is of accurately formed cylindrical shape, such that when it is positioned in the location hole 228, part of it projects slightly over the cut-out 226. Finally, the jig is equipped with first and second adjustable fences 240 and 242 which can be attached to the front edge 224 of the jig.

Supposing that it is required to profile grind a cutter such as the cutter 14 illustrated in Figs. 1 and 2, or the cutter 62 illustrated in Figs. 3 and 4, the template, which will be formed as shown in Fig. 5 (excepting of course that the profile will vary according to the article which is to be produced on the woodworking machine) is positioned on the table 11 6, and secured by the clamp 11 8. A cutter blank 216 is then located against the stationary fence 214, and the table 11 6 is moved rearwardly, until the deepest portion of the template is engaged with the stylus 124, as illustrated in Fig. 7. The cutter blank 216 is then slid rearwardly on the obverse face 202 of the element 200, until it is just touching the periphery of the grinding wheel 100.It will be recollected, that the forward position of the periphery of the grinding wheel is fixed relatively to the stylus 124. The fence 218 is then engaged with the forward edge of the cutter blank 216, and the clamp 220 used to secure the cutter blank to the jig.

Next, it may be necessary to carry out lateral or axial adjustment of the stylus 124, and this can be done as shown in Fig. 9. First the locating edge of the cutter blank which is engaged with the stationary fence 214 is engaged with the left hand side of the grinding wheel as shown in Fig. 9. With the jig in this position, the stylus is adjusted axially (as described in the Specification of Patent Application No: Case D) until it engages with the edge 91 of the template. Once this has been done, both the machine and the jig are properly set for carrying out the profile grinding operation.This is done by turning the handwheel 132, so that the rear edge of the cutter blank rests on the top edge of the guide plate 148, and then manipulating the floating table 11 6, so that the profile surface of the template is maintained in contact with the stylus 124. whilst the table is traversed longitudinally. The effect of this is to cause the grinding wheel 100 to grind a profile into the rear portion of the blank 216, similar to the profile 92 on the template. In practice, the grinding wheel may be tilted to give the necessary cutting angles, but it is not necessary to explain this in detail, as it does not form part of the present invention.

It is then necessary, to form the notches 30 and 32, or the notch 78, so as to maintain the distance H as previously described. For this purpose, the peg 238 is first fitted into the location hole 228, and then the template 90 is placed against a stationary fence 225 extending along the front edge 224 of the element 200, with one end of the portion 94 of the template resting against the stop peg 238. The first fence 240 is then brought into engagement with the opposite end of the portion 94 of the template 90 as illustrated in Fig. 10, and the fence 240 is locked in this position.

Then, the template 90 is removed, and so is the stop peg 238, it is then possible to place the cutter 216, which is now formed with a profiled edge 217, resting against the fence 225, and with the deepest part of its profile resting against the first fence 240. In this position, which is illustrated in Fig. 11, the cutter blank 216 almost completely overlies the cut-out 226. At this stage, the second movable fence 242 is brought into engagement with the edge 219 of the cutter blank opposite to the profiled edge 217, and the second fence is locked in this position. A conventional clamp 250 is then used to secure the cutter blank in this fully located position adjoining the front edge of the element 200.

The handwheel 132 is then used to rotate the shaft 130 through approximately 180t so as to bring the reverse face 204 of the element 200 to the top side. This reversal, also has the effect of bringing the front edge 224 of the element 200 to the rear, facing the grinding wheel 100, but owing to the inclined arrangement of the edge 224, the left hand end of the element 200 is then further to the rear than the right hand end.

A notching stylus 252 (see Fig. 12) is also provided on the grinding machine, but it has been omitted from Fig. 6 for clarity. The notching stylus 252 occupies a fixed location on the grinding machine, and this means that it is fixed relatively to the location of the front part of the periphery of the grinding wheel 100.

In order to carry out a notching operation, the table 116 is manipulated, so that the notch 234 in the template 232 follows the stylus 252, and this causes the grinding wheel 100 to reproduce the shape of the notch 234 in the cutter blank, as illustrated in Fig. 12. Now it is to be noted, that since the locating edge of the cutter blank which is engaged with the fence 225 is inclined relatively to the grinding wheel 100, the latter grinds on its periphery rather than its flank, and this is a significant feature, because it is practically impossible to grind accurately with the flanks of the grinding wheel. Furthermore, it would be dangerous to attempt to grind with the flanks of the grinding wheel 100.

Whilst the general shape of the notch which is produced by this method is not particularly significant, so long as it provides ample space for the projections 36 or 38, or the pin 76 as the case may be, it is important that the edge of the notch which is remote from the profile ground edge of the cutter shall be perpendicular to the side edges of the cutter blank, because this is the edge which provides the location face as described above with reference to Figs. 1 to 4 of the drawings.

If it is necessary to grind two notches one at each side of the cutter blank-for example as shown in Fig. 2-then once the notch has been formed by the method described above, the cutter blank is removed from the jig, turned over to bring its opposite locating edge into engagement with the stationary fence 225, and the notching process is repeated.

Whenever it is necessary to re-grind the cutter because it has become worn, then the profile grinding operation is carried out exactly as described above, with reference to Figs. 7, 8 and 9 of the drawings. Then the cutter blank is placed on the jig in the position illustrated in Fig. 11, with the newly ground profile edge engaged with the first adjustable fence 240. Because a certain amount of material will have been removed from this edge, there is then a slight clearance between the opposite edge 219 of the cutter and the adjustable fence 242, but the latter is then moved so that it again engages with and locates the cutter blank. The jig is then inverted as previously described, and the notched template 232 is engaged with the notching stylus 252. However, since the notch will then be formed in the cutter, it is only necessary to utilise the edge of the notch in the template which is perpendicular to the front edge 224 of the element 200, and this has the effect of re-grinding only the location edge in the notch. Now since the distance between the fence 240 and the grinding wheel 100, has not altered, despite the regrinding of the profile of the cutter, the result is that the distance H is maintained as required.

Claims (13)

1. A method of locating a cutter in a cutter head for use in a machine tool comprising the steps of: forming a cutting edge on the cutter; forming a location edge on the cutter having a determined spacial relationship to the cutting edge; and securing the cutter in the cutter head with the location edge abutting a stop which occupies a fixed position on the cutter head.

2. A method as claimed in Claim 1, comprising the further steps of: removing the cutter from the cutter head; reforming the cutting edge on the cutter; reforming the location edge on the cutter to maintain the determined spatial relationship between the cutting edge and the location edge and then re-securing the cutter in the cutter head with the location edge abutting the stop, whereby the relationship of the cutting edge to the cutter head remains the same despite reforming of the cutting edge.

3. A method of locating two or more cutters in a rotatable cutter head for use in a machine tool, wherein the method of Claim 1 is employed for each cutter, so that both or all the cutting edges have the same spatial relationship to the rotational axis of the cutter head.

4. A cutter head for use in a machine tool, in which there are two or more cutters, each having the same cutting profile formed thereon, each cutter having a locating edge engaging with a respective stop, which stops occupy fixed positions on the cutter head, the arrangement providing that both or all the cutting profiles occupy the same spatial relationship to the axis of rotation of the cutter head.

5. A cutter head as claimed in Claim 4, in which there are two or more laterally spaced stops engaging with laterally spaced locating edges whereby rocking of the cutter is prevented.

6. A method of grinding a cutting edge and a location edge on a cutter for use in a cutter head of a machine tool to ensure that the spacial relationship between the cutting edge and the location edge is repeatable, comprising the steps of: grinding a cutting edge on the cutter; establishing a temporary datum position on a jig having a determined spatial relationship to the jig by means of a removable stop; engaging one edge of a template with the removable stop; engaging a first fence with an opposite edge of the template to establish a determined distance between the temporary datum position and the first fence; removing the stop and the template; engaging the cutting edge of a cutter with the first fence; engaging a second fence with the edge of the cutter opposite to the cutting edge; securing the cutter to the jig; presenting the jig to a grinding machine with a notched template part of the jig engaging with a stylus occupying a predetermined fixed position relatively to the effective edge of the grinding wheel on the machine, and moving the jig so that the notch template slides over and in engagement with the stylus and the shape of the notch is ground by the grinding wheel into the cutter, to produce a location edge on the cutter which has a relationship to the cutting edge thereon determined by the relationship between the datum position and the template on the jig.

7. A method as claimed in Claim 6, comprising the further steps of: re-grinding the cutting edge of the cutter; re-locating the cutter on the jig with its cutting edge in engagement with the first fence on the jig; adjusting the second fence to engage it with the said opposite edge of the cutter; clamping the cutter to the jig and re-presenting the jig to the grinding machine to re-grind the notch to produce a fresh location on the cutter having the same relationship to the cutting edge as that obtained at the previous presentation of the jig to the grinding machine.

8. A jig for grinding a cutting edge and a location edge on a rectangular plate-like cutter having a cutting edge and a location side edge at right angles to the cutting edge, the jig comprising a plate carried on an axle mounting and having on its obverse side primary fence means for locating a cutter with its cutting edge parallel with the axis of the axle mounting, and secondary fence means for locating a cutter with its locating side edge inclined with respect to the axis of the axle mounting, the plate having a cut-away portion opening to one edge of the jig and positioned so that it coincides with part of a cutter engaging with the secondary fence means and a notched template part projecting from the edge of the jig plate which has the cut-away.

9. A jig as claimed in Claim 8, in which the notched template is adjustable on the jig plate in a direction parallel with the cutting edge of a cutter engaging with the secondary fence means.

10. A method of locating a cutter in a cutter head for use in a machine tool as claimed in Claim 1, substantially as herein described with reference to Figs. 1, 2 and 5 to 12 of the accompanying drawings, or with reference to Figs. 3 to 12 of the accompanying drawings.

11. A method of locating two or more cutters in a rotatable cutter head for use in a machine tool substantially as herein described with reference to Figs. 1. 2 and 5 to 12. or with reterence to Figs. 3 to 12 of the accom panying drawings.

12. A cutter head for use in a machine tool as claimed in Claim 4, constructed and arranged substantially as herein described with reference to Figs. 1 and 2 or Figs. 3 and 4 of the accompanying drawings.

13. A jig as claimed in Claim 8, constructed and arranged substantially as herein described with reference to Figs. 7 to 12 of the accompanying drawings.