WO2006075161A1

WO2006075161A1 - Slot cutting apparatus

Info

Publication number: WO2006075161A1
Application number: PCT/GB2006/000104
Authority: WO
Inventors: Derek Quinton
Original assignee: Derek Quinton
Priority date: 2005-01-12
Filing date: 2006-01-12
Publication date: 2006-07-20
Also published as: GB0500595D0; EP1846200A1; GB2422132A; GB2422132B

Abstract

A slot cutting jig (2) comprises a base plate (4) mountable for reciprocating movement relative to a cutting device 16. The base plate (4) has an opening (24) formed therein to receive the cutting bit (32) of the cutting apparatus (16). The jig further comprises a backing member (6) upstanding from the base plate 4 for receiving a workpiece (62) thereagainst; and a guide member (8) adjustably mounted adjacent the opening (24) for receiving a slot (64) formed in said workpiece (62) in order correctly to position the workpiece for cutting of a subsequent slot.

Description

Slot Cutting Apparatus

The present invention relates to slot cutting apparatus, and in particular to a jig for use in cutting slots.

In the woodworking art it is frequently necessary to produce spaced slots in a workpiece for making joints. The slots may be parallel sided or dovetail in shape, depending on the particular joint being produced. A number of jigs are known for this purpose. These usually involve a comb - like template with which a router engages to form the slot. However, these existing jigs are difficult and time consuming to setup for use..

The present invention therefore seeks to provide a slot cutting jig which facilitates the set-up and use of the jig. From a first aspect, therefore, the present invention provides a slot cutting jig comprising a base arranged or arrangable for relative reciprocating movement between the jig and a cutting device; said base having an opening formed therein to receive the cutting bit of the cutting device; a backing member upstanding from said base for receiving a workpiece thereagainst; and a guide member adjustably mounted adjacent said opening for receiving a slot formed in said workpiece in order correctly to position the workpiece for the cutting of a subsequent slot.

Thus in accordance with the invention, a guide member is provided which locates in a slot cut into the workpiece. A further slot may then be cut into the workpiece, whereafter, the newly cut slot can be located over the guide member in order to accurately position the workpiece for the next slot cut. The guide member's position relative to the base opening, and therefore relative to the cutter can be varied whereby the initial position of the guide member can be varied to give the appropriate spacing between the slots.

A specific guide member is preferably used for a specific slot width, and the initial position of that guide member can be adjusted as appropriate. This facilitates the initial set up of the jig irrespective of the size of slot being cut. From a further aspect, therefore, the invention provides a slot cutting jig comprising a base arranged or arrangable for relative reciprocating movement between the jig and a cutting device; said base having an opening formed therein to receive the cutting bit of the cutting device; a backing member upstanding from said base for receiving a workpiece there against; and a plurality of guide members interchangeably mountable on said base adjacent said opening for receiving a slot formed in said workpiece in order correctly to position the workpiece for cutting of a subsequent slot.

From a yet further aspect, therefore, the invention provides a slot cutting jig comprising a base arranged or arrangable for relative reciprocating movement between the jig and a cutting device; said base having an opening formed therein to receive the cutting bit of the cutting device; a backing member upstanding from said base for receiving a workpiece there against; said base having means for adjustably or replaceably receiving a guide member thereon, said guide member receiving a slot formed in said workpiece in order correctly to position the workpiece for cutting of a subsequent slot.

Preferably the jig further includes a setting member which is locatable along the axis of the cutter and which cooperates with the guide member in order to set the initial position of the guide member. Preferably, the guide member is configured such that an edge of the guide member abuts the setting member in order to set the initial position of the guide member.

In the preferred embodiment, the setting member comprises a cylindrical pin which is received in a chuck of the cutting apparatus.

Alternatively, rather than the setting member being a member which is ^■ locatable along the axis of the cutter, it may be a member which is interposed between the cutter axis and the guide member. For example, it may simply be a member of the appropriate width interposed between the cutter and the guide member. In one embodiment, the setting member may comprise a member having a slot formed therethrough which is sized to fit over the cutter and other means for cooperating with the guide member. An edge of the setting member may abut the guide member, but in the preferred embodiment, the setting member comprises a further slot at the appropriate distance from the first slot which engages over the guide member to position it.

From a further aspect, the invention provides a setting member for a slot cutting jig, comprising a pair of slots formed in an edge thereof at a predetermined spacing from one another, said slots corresponding in size to slots to be formed in a workpiece.

A single setting member may be usable with a plurality of guide members. With such an arrangement, the position of the workpiece location part of the guide member should be positioned appropriately, e.g. with respect to the edge of the guide member which engages with the setting member. However, if a setting member having slots corresponding to specific cutter sizes is used, then a separate setting member will be needed for each slot shape. To slots of different sizes may be provided on different edges of the member.

Preferably, the guide member is formed on a slide member which can be moved towards and away from the base opening to vary the position of the guide member.

Preferably, therefore, the base comprises a key way for receiving the guide member.

The guide member will be provided with a cross-section and size appropriate to the intended slot shape, and may therefore, be rectangular or dovetailed in section. It may be formed as a tooth, preferably set back from the edge of the slide by a predetermined amount which is taken into account when setting the initial position of the guide member. Also, as discussed above, the offset of the tooth may vary from guide member to guide member where a single setting member is used. In the case of rectangular slots, the guide preferably has a sloping surface arranged towards the backing member thereby facilitating insertion of the workpiece over the guide tooth. This also allows for accurate positioning of workpieces of different thick nesses.

The backing member may be formed as a plate, having an opening formed therein to allow passage of the cutter.

The backing member may be in a fixed position relative to the base, but preferably it is mountable at a range of angles relative to the base so as to allow slots to be cut an angle on the edge of a workpiece, as may be required when forming joints at angles other than a right angle.

This is in itself a novel arrangement, so from a further aspect, the invention provides a slot cutting jig comprising a base arranged or arrangable for relative reciprocating movement between the jig and a cutting device, said base having an opening formed therein to receive the cutting bit of the cutting device; a backing member upstanding from said base for receiving a workpiece there against; and a guide member positioned adjacent said opening for receiving a slot formed in said workpiece in order correctly to position the workpiece for cutting of a subsequent slot, wherein the backing member it is positionable at a range of angles relative to the plane of the base.

In a preferred embodiment, the backing member is pivotally mounted with respect to the base, having means for selectively retaining the backing member in one or more angular positions relative to the base. The retaining means may comprise one or more clips, pins or screws which engage between the backing member and the base.

Preferably the backing member comprises a front plate and a pair of opposed side plates. Most preferably the side plates are provided with the means for retaining the backing member in a range of positions, e.g. a plurality of holes to receive the aforementioned pins or screws. An alternative to a plurality of holes would be an arcuate slot. This would potentially give greater flexibility in the range of positions settable. The base may be provided with side plates which cooperate with the backing member side plates.

As mentioned above, the jig is intended to be reciprocated relative to a cutting device. Preferably the jig is used in combination with a router. Routers normally have a base whose position relative to the router body is variable towards and away from the router body in order to vary the depth of cut produced by the router cutter. In a preferred embodiment of the invention, the jig is mounted to the router base plate so as to be reciprocal relative thereto. In the preferred embodiment, the jig base is provided with aligned bores to receive a pair of rails mountable to the router base plate and along which the jig may be moved. Preferably the rails are provided with stop members which limit the reciprocating movement of the jig on the router.

Preferably the bores are formed in bushings . Preferably the bushings are configured to accommodate different spacings between the guide rails. In one embodiment, the bushings may comprise eccentric bores, the appropriate spacing being set by suitable positioning of the bushings. Alternatively, a range of bushings having openings specific to a particular spacing may be interchangeably mounted on the jig.

Other router mounting arrangements are known, however. In North America, for example, it is common to mount a router under a table which has an opening for the router bit. A workpiece is then moved manually over the table to effect the cut. In a further preferred embodiment of the invention, the base is mounted reciprocably on a table which supports the cutting device.

Preferably, the table comprises guide surfaces for receiving the base of the jig. Most preferably the edges of the base are received in guides provided in or on the table.

Preferably the table further comprises means for limiting the longitudinal movement of the base. Various such means can easily be envisaged by the skilled person, but in one embodiment, the table is provided with a series of apertures arranged longitudinally for receiving stop members e.g. pins. Respective rows of apertures may be provided on either side of the table, and preferably these rows are offset longitudinally from one another to allow for a finer control of the base movement.

The table may comprise suitable means to receive and locate the cutting device.

Means may also be provided for aligning the cutting device relative to the jig. This may comprise a member locatable in a reference position in the jig and having a part which is locatable in the cutting device, whereupon the cutting device can be located relative to the jig. The table may be fittable to some other support surface, or may itself be provided with legs to support it. Some preferred embodiments of the invention will now be described by way of example only with reference to the accompanying drawings in which:

Figure 1 shows a perspective view of a jig in accordance with the invention in set up mode; Figure 2 shows the jig of Figure 1 in a cutting mode;

Figure 3 shows a side view of the jig of the invention mounted on a routing machine;

Figures 4a, 4b and 4c show top, side and end views of the base plate of the jig of Figure 1; Figures 5 a, 5b, 5c, 5d, 5e show a range of guide members for cutting different slot shapes, Figure 5e being a side view of the guide members of Figures 5a TO 5c; Figure 6 shows the setting pin of the apparatus; Figure 7 shows alternative rail mounting arrangements;

Figures 8a to 8d illustrate the use of the jig of Figure 1 Figures 9a to 9d show the set up of the apparatus using a different setting member;

Figure 10 shows a second jig in accordance with the invention;

Figure 11 shows a detail of the jig of Figure 10;

Figure 12 shows the table supporting the jig of Figure 10; and Figure 13 shows a setting member for use with the jig of Figure 10

With reference to Figures 1 to 3, a jig 2 in accordance with the invention comprises three main components, namely a base plate 4, a backing member 6 and an adjustable guide member 8.

The base plate 4 is formed with a pair of downwardly depending flanges 10 which receive a pair of guide rails 12 which, as shown in Figure 3, extend through and are clamped in, the base plate 14 of a router 16. The router used can be of any known type. A Power Devil Model PDW5037PR is one router suitable for use with the jig.

As shown in Figures 4b and 4c, each flange 10 has an opening 18 which it receives a bush 20 e.g. of PTFE, allowing the base plate 4 to slide smoothly along the guide rails 12. Stops 22 are provided at opposite ends of the guide rails 12 to limit the range of movement of the jig 2 on the guide rails 12. The guide receiving bore 21 of each bush 20 is eccentric relative to the centre of the bush so as to allow for differences in the spacing between the guide rails 12. This may be necessary as the spacing between the openings receiving the guide rails 12 in the router base plate 14 may vary from router to router. The bushes 20 are retained by set screws 23. The base plate 4 further comprises an elongate slot 24 running parallel to the guide rails 12. One end 26 of the slot 24 is enlarged to facilitate access to the chuck of the underlying router 16. A keyway 28 is formed on one side of the base plate 4 extending between an edge 30 of the base plate and an inside edge 32 of the slot 24. This keyway 28 receives the guide member 8. The backing member 6 comprises a front plate 34 having an opening 36 to allow the passage of a drill bit 38 of the router 16. The backing member 6 is pivotally mounted to the base plate 4 by pins 40 engaging in bores 42 provided in the edge of the base plate 4. The backing member 6 further comprises a pair of arcuate slide plates 44. The rear edge of each side plate 44 is provided with a series of aligned openings 46 which allow the angle of the backing member 30 relative to the plane of the base member 4 to be adjusted. In particular, the angle is set by rotating the backing member 6 around the pins 40, the position of the backing member 6 being fixed by further pins 48 engaging through the relevant holes 42 in the side plates into bores 50 in the base plate 4. In the particular embodiment shown, the holes 46 are placed at angles of 18°, 30°, 38.57° and 45°. This will allow a range of different joint slots to be cut.

The guide member 8 is formed as a slide member 52 having an upstanding tooth 54 provided at one end of the slide member 52. In the embodiment shown in Figure 1, the guide tooth 54 is for forming a rectangular slot in a workpiece and the width of the tooth corresponds to the desired width of the slot. To facilitate positioning of the workpiece over the tooth 54, the rear edge 56 of the tooth is angled downwardly towards the base plate 4 at an angle of about 45°. The guide tooth 54 is off-set slightly from the edge 58 of the slide member 52. This off-set is automatically compensated for during setup of the jig. As shown in Figures 5a to 5d, different sized teeth 54, 54', 54", 54'" can be used to produce different sized and shaped slots. In each case, the tooth 54 is off-set from the edge 58 of the slide member 52, the amount of off -set differing from tooth to tooth.

Referring now to Figure 6, a setting pin 60 for use in the jig 2 comprises a small diameter portion 62 which is received in the router chuck and a larger diameter portion 64 which projects up into the base plate slot 24 for abutting the edge 58 of the slide member 52 in order to set the initial position of the guide tooth 54 tooth as will be described further below. The same setting pin 60 is usable with each of the slide members 52 shown in Figures 4a to 4d. That is the reason for the different offsets of the teeth 54 from the edge 58 of the slide members 52. This considerably facilitates use of the equipment as only a single setting pin is required Figure 7 illustrates two alternative mechanisms for receiving the guide rails 12 in the jig. Instead of eccentric bushes 20 as discussed above, a bush 74 having a rail receiving opening 76 may be inserted into a slot 76 formed in the edge of the base plate flange 10. Different bushes 74 may be used depending on the spacing between the guide rails. Alternatively, a bush 80 may be used which is inserted into an opening 82 in the flange 10. The position of the guide rail receiving opening 84 is fixed in the bush, but different bushes 80 may be used for different guide rail spacings.

Operation of the jig will now be described. In order to cut a series of slots 68 in the edge of a workpiece 66, the appropriate guide member 8 must first be chosen. The setting pin 60 is located in the router chuck through the enlarged portion 26 of the base plate slot 24, as shown in Figure 8a and tightened in position. In this position, the router is in its bottom most position as shown in Figure 3. In this position the larger diameter portion 64 of the guide setting pin 60 sits within the base plate slot 24. The edge 58 of the slide member 52 is then moved into contact with the setting pin 60, as shown in Figure 8a whereupon the position of the slide member 52 is fixed by tightening a fixing member, e.g. a screw 70. The diameter of the setting pin 60 and the off-set of the guide tooth 54 from the edge 58 of the slide member 52 ensure the correct spacing between slots in the cut workpiece. After the position of the guide tooth 54 has been set as described above, the setting pin 60 is removed from the chuck and the appropriate routing bit 38 (which will have the same diameter dimension as the width dimension of the guide tooth 54) inserted into the chuck. The appropriate depth of slot cut can then be set by placing a member 84 of the desired cut depth on the base plate 4, overlapping that member 84 with a reference member 86 which overlies the cutter bit 38, as shown in Figure 8b and moving the base plate of the router up and down using its known adjustment mechanism until the tip of the bit 38 touches the reference member 86. The position of the router base plate 18 is then fixed in the normal way. A slot 68 can now be cut in the workpiece 66. To cut the first slot 68 in the workpiece 66, a straight edge of the workpiece 66 is placed against the inwardly facing surface 72 of the guide tooth 54 and its surface placed against the front plate 34 of the backing member 6. The workpiece 66 may be retained against this surface by hand or a clamp can be used, if required. The base plate 4 is then reciprocated along the guide rails 12 in order to make the cut, as shown in Figure 8c. Once a slot 68 has been cut in the workpiece 66, that slot 68 can then be engaged over the guide tooth 54 with the workpiece 66 clamped or held against the front plate 34 of the backing member 6 and the base plate 4 reciprocated once more to cut the adjacent slot 68. The procedure is repeated until all necessary slots have been cut.

To cut slots in a workpiece 88 for assembly to the workpiece 66, the last slot 68 formed in the workpiece 66 is placed over the guide tooth 54 and the workpiece 84 moved to abut the edge of the workpiece 66, and a cut made as shown in Figure 8d. The process then continues as before on the workpiece 88. Should a different size of slot 68 be required then the guide member can be replaced by another guide member which is set up using the appropriate setting pin 60.

Referring to Figures 9a to 9d, an alternative arrangement is shown.

In this arrangement, for cutting dovetails (but equally applicable to other slot shapes), a router bit 100 is first placed loosely in the router chuck, as illustrated in Figure 9a. A setting member 102 is then used to set the initial position of a slide member 104, having a dovetail guide tooth 106. The setting member 102 is formed as a plate 108 having a pair of precision formed slots 110 formed adjacent an edge 112 of the plate 108, A notch 113 is formed at that edge 112 also. The slots 108 correspond in shape to the shape of the router bit 100 and are placed at a spacing from one another corresponding to the spacing between the slots to be cut in a workpiece 114.

A second pair of slots 110a is provided on the opposite corner of the plate 108. These slots 110a correspond to a different dovetail size, whereby a single setting member 102 can be used for more than one dovetail.

The slots 108 are placed over the router bit 100 and guide tooth 106 as shown in Figure 9b and the router bit 100 then tightened in its chuck and the slide member fixed in position. This sets the correct spacing between the router bit 100 and the guide tooth 106 and the correct depth of cut.

The setting member 102 is then moved to the position shown in Figure 9c, with the slot previously over the router bit 100 now positioned over the guide tooth 106. A workpiece 114 is then positioned against the edge 112 of the plate 108 and a first cut 116 made, as shown in Figure 9d. The next cut is made with the cut 116 engaged with the guide tooth 106. Subsequent cuts are made with the newly made cut being engaged over the guide tooth 106.

Figures 10 to 12 describe a second embodiment of the invention. In this embodiment, the jig 200 is mounted for reciprocating movement on a table member 202, rather than on rails, as in the previous embodiment. Such an arrangement may be more appropriate for use in areas such as North America where it is common to mount a router on a table which is supported in a suitable aperture in a workbench or other surface. The jig 200 comprises essentially similar components to that of the earlier embodiments, namely a base plate 204 having a slot 206 for accommodating the router bit, and an adjustable backing member 208. The backing member 208 has segment shaped side plates 210 which are locatable relative to segment shaped supports 212 upstanding from the base plate 204. The base plate 204 also mounts a slide member 214, as shown inFigure 11.

The slide member 216 is similar to that of the first embodiment, except that it is shaped as a half dovetail, with a square face 218 and an angled face 220. The base plate 204 has as complementary slot 222 receiving the slide member 216. The slide member 216 is located in position by a screw 224 which can be tightened and loosened through the end of the base plate 204. This is necessary since the under surface of the jig 200 is not accessible in this embodiment. The base plate 204 also has a pair of upstanding pins 228 which can be used to move the jig 200 on the table 202.

The table member 202 shown in Figure 12 comprises a pair of guide rails 228 each formed with a V-shaped groove 230 for receiving, supporting and guiding complementarily shaped edges 208 of the base plate 204. The guide rails 228 are provided with holes 232 for fixing the table in a work surface or for attaching supporting legs or the like. The guide rails may extend longitudinally or transversely of the table, as appropriate.

A pair of rails 234 is arranged inwardly of the guide rails 228. These rails 234 are provided with rows of holes 236. The holes 236 receive stop pins 240 which in use limit the range of movement of the jig 200. The adjacent rows at either end of the table may be longitudinally offset from one another so as to allow for a finer control of the positioning of the pins and thus the range of movement of the jig. The table 202 also comprises a number of holes 242 outboard of the rails 242 to receive screws or other fasteners for clamping a router to the underside of the table 202.

The jig 200 of this embodiment is set up and used in a similar manner to that of the first embodiment. As a first step, however, it is necessary to properly align the router bit with respect to the jig 200. This is effected using a bit setting tool 244, shown in Figure 13. The bit setting tool 244 comprises an elongate portion 246 for insertion into the router chuck, and a coaxial cylindrical portion 248 which is designed to be a tight fit in the circular portion 250 of the slot 206 formed in the base plate 200. A further cylindrical portion 252 allows the tool to be gripped. To align the router bit, the tool 244 is positioned in the slot 206 and the router brought up to receive the elongate portion of the tool 244 in its chuck, which is then tightened. The router can then be secured to the underside of the table 202 by suitable clamping means. The chuck can then be loosened, the bit setting tool 244 removed and a router bit then placed in the chuck. Cutting can then be set up in the same manner as disclosed in. either of the earlier embodiments.

It will be seen, therefore, that the invention will allow a series of slots to be cut in a workpiece with minimal set up and with ease of use. It will also accommodate cutting slots at a range of angles relative to the edge of a workpiece, allowing for angled joints between workpieces.

It will be appreciated that the jig of the invention can also be used to perform other functions. For example, the cutter may be substituted with a biscuit slot cutter which can be used to cut a biscuit slot into the side of a workpiece. Also the jig can accommodate a full range of standard cutters and drill bits.

Also, the backing member may be retained in position using other mechanisms than those disclosed, such as sprung pins, clips or the like.

The jig may be made from any suitable material, for example metal or high strength plastics materials. The jig may be moved relative to the cutting apparatus, or vice versa. All that is necessary is that the mounting of the jig accommodates such relative movement.

A feeler gauge, shim or the like may be used in conjunction with the setting member in order to adjust the fit of a joint produced using the slots. This may be desirable in that different materials may expand or contract during or after cutting or may, due to their hardness, deflect the cutting tool during cutting. This may result, for example, in a slot being cut wider than the diameter of the cutting tool. To compensate for this, the feeler gauge etc. of the expected difference in dimension may be interposed between the setting member and the guide member during set up, so as to produce a larger than nominal spacing (corresponding to the cut width) between teeth.

Claims

1. A slot cutting jig comprising a base arranged or arrangable to permit reciprocating movement between the jig and a cutting device; said base having an opening formed therein to receive the cutter of the cutting device; a backing member upstanding from said base for receiving a workpiece thereagainst; said base having means for adjustably or replaceably receiving a guide member thereon, said guide member receiving a slot formed in said workpiece in order correctly to position the workpiece for cutting of a subsequent slot.

2. A slot cutting jig comprising a base arranged or arrangable to permit relative reciprocating movement between the jig and a cutting device; said base having an opening formed therein to receive the cutter of the cutting device; a backing member upstanding from said base for receiving a workpiece there against; and a guide member adjustably mounted adjacent said opening for receiving a slot formed in said workpiece in order correctly to position the workpiece for cutting of a subsequent slot.

3. A jig as claimed in claim 2 wherein said jig is adapted to receive a plurality of interchangeable guide members .

4. A slot cutting jig comprising a base arranged or arrangable to permit relative reciprocating movement between the jig and a cutting device; said base having an opening formed -therein to receive the cutter of the cutting device; a backing member upstanding from said base for receiving a workpiece there against; and a plurality of guide members interchangeably mountable on said base adjacent said opening for receiving a slot formed in said workpiece in order correctly to position the workpiece for cutting of a subsequent slot.

5. A jig as claimed in any preceding claim, further comprising a setting member which cooperates with the guide member in order to set the initial position of the guide member.

6. A jig as claimed in claim 5 wherein said setting member is locatable along the axis of the cutter.

7. A jig as claimed in claim 5 or 6, wherein the guide member is configured such that an edge of the guide member abuts the setting member in order to set the initial position of the guide member.

8. A jig as claimed in claim 6 or 7, wherein the setting member comprises a cylindrical pin which is received in a chuck of the cutting apparatus.

9. A jig as claimed in any of claims 5 to 8, wherein a single setting member is usable with a plurality of guide members .

10. A jig as claimed in claim 5 wherein said setting member comprises a member having a slot formed therethrough which is sized to fit over the cutter and other means for cooperating with the guide member.

11. A jig as claimed in claim 10 wherein the said cooperating means comprises a further slot for engagement with the guide member.

12. A jig as claimed in claim 10 or 11 comprising slots of different sizes provided on different edges of the member.

13. A jig as claimed in any preceding claim, wherein the guide member is provided on a slide member which can be moved towards and away from the base opening to vary the position of the guide member.

14. A jig as claimed in claim 13, wherein the base comprises a key way for receiving the slide member.

15 A jig as claimed in any preceding claim wherein the guide member is rectangular or dovetailed in section

16. A jig as claimed in any preceding claim wherein the guide member comprises a tooth.

17. A jig as claimed in claim 16 as dependent directly or directly upon claim 10, wherein the tooth is set back from the edge of the slide member.

18. A jig as claimed in claim 15, 16 or 17 wherein the guide member has a surface which slopes downwardly towards the backing member.

19. A jig as claimed in any preceding claim wherein the backing member comprises a plate having an opening formed therein to allow passage of the cutter.

20. A jig as claimed in claim 19 wherein the backing member is fixed relative to the base.

21. A jig as claimed in claim 19, wherein the backing member is mountable at a range of angles relative to the base.

22. A slot cutting jig comprising a base arranged or arrangable to permit relative reciprocating movement between the jig and a cutting device, said base having an opening formed therein to receive the cutting bit of the cutting device; a backing member upstanding from said base for receiving a workpiece there against; and a guide member positioned adjacent said slot for receiving a slot formed in said workpiece in order correctly to position the workpiece for cutting of a subsequent slot, wherein the backing member it is positionable at a range of angles relative to the plane of the base.

23. A jig as claimed in claim 21 or 22 wherein the backing member is pivotally mounted with respect to the base.

24 . A jig as claimed in claim 21, 22 or 23, having means for selectively retaining the backing member in one or more angular positions relative to the base.

25. A jig as claimed in any preceding claim wherein the backing member comprises a front plate and a pair of opposed side plates.

26. A jig as claimed in claim 25 wherein the side plates are provided with means for retaining the backing member in a range of positions.

27. A jig as claimed in any preceding claim comprising means guiding relative reciprocating movement of the jig and a cutter.

28. A jig as claimed in any preceding claim, wherein the base is provided with aligned bores to receive a pair of rails along which the jig may reciprocate.

29. A jig as claimed in claim 28 wherein the bores are formed in bushings.

30. A jig as claimed in claim 29, wherein the bushings are configured to accommodate different spacings between the guide rails .

31. A jig as claimed in claim 30, wherein the bushings comprise eccentric bores.

32. A jig as claimed in claim 30, wherein a range of bushings having openings specific to a particular spacing are interchangeably mounted on the jig.

33. A jig as claimed in any of claims 27 to 31, wherein the rails are provided with stop members which limit the reciprocating movement of the jig.

34. A jig as claimed in any preceding claim mounted on or to a router.

35. The combination of claim 34 including a jig as claimed in any of claims 24 to 29, wherein the rails are mounted to a router base.

36. The combination of claim 34 or 35 wherein the vertical spacing between the router and the jig is adjustable.

37. A jig as claimed in claim 27 wherein said base is mounted for reciprocating movement on a table which supports the cutting device.

38. A j ig as claimed in claim 37 wherein the table comprises guide surfaces for receiving the base of the jig.

39. A jig as claimed in claim 38 wherein longitudinal edges of the base are received in guides provided in or on the table.

40. A jig as claimed in any of claims 37 to 39 wherein the table further comprises means for limiting the reciprocating movement of the base.

41. A jig as claimed in claim 40 wherein the table is provided with a series of apertures arranged for receiving stop members.

42. A jig as claimed in claim 41 wherein respective rows of apertures are provided on either side of the table.

43. A jig as claimed in claim 42 wherein these rows are offset from one another in the direction of reciprocating movement.

44. A jig as claimed in any of claims 37 to 43 wherein said table comprises means to receive and locate the cutting device.

45. A jig as claimed in claim 44 further comprising means for aligning the cutting device relative to the jig.

46. A setting member for a slot cutting jig, comprising a pair of slots formed in an edge thereof at a predetermined spacing from one another, said slots corresponding in size to slots to be formed in a workpiece.

47. A setting member for a slot cutting jig comprising a first cylindrical portion for insertion into a chuck of a cutting device and a second, coaxial cylindrical portion for engagement with a guide member or opening of the jig.

48. A slot cutting jig comprising a base arranged or arrangable to permit reciprocating movement between the jig and a cutting device; said base having an opening formed therein to receive the cutter of the cutting device; a backing member upstanding from said base for receiving a workpiece thereagainst; and a guide member adjustably or replaceably mounted on said base, said guide member receiving a slot formed in said workpiece in order correctly to position the workpiece for cutting of a subsequent slot.