Improvements in cutting tool mounting assemblies

This invention relates to a jig for mounting a cutting tool, in particular though not exclusively, a router.

Hand-held routers are usually used by moving the tool relative to a fixed workpiece, often using a fence or template to guide its movement. It can be difficult, however, to produce accurate cuts across thin or small workpieces.

The present invention provides a jig for mounting a cutting tool such as a router, said jig comprising a carriage having means for attaching a cutting tool thereto in use, first track means for guiding movement of said carriage along a first path, second track means for guiding movement of said carriage along a second path perpendicular to said first path, the jig further comprising means for attachment of the jig to a workpiece holding device such as a portable work bench, in use.

By way of example, embodiments of the invention will be described with reference to the accompanying drawings, in which:

Figure 1 illustrates an embodiment of a jig according to the present invention,

Figure 2 illustrates the jig of Figure 1, with a router mounted thereon,

Figure 3 illustrates the jig of Figure 2 with the router in its inoperative position,

Figure 4 is an exploded view illustrating the main components of the jig of Figures 1, 2 and 3,

Figure 5 illustrates a further alternative use of the jig of Figures 1 to 4, and

Figures 6, 7, 8 and 9 illustrate a modified version of the jig of Figures 1 to 5.

A jig 10 for mounting a cutting tool is seen in Figures 1 and 2. The cutting tool may be a typical hand-held electrically powered plunge router 11 (see Figure 2), as used by many woodworkers and DIY enthusiasts.

The router 11 is fixed to a platen 12 on the jig 10 by suitable means such as bolts. As will be seen, the platen 12 has a hole 13 therein to enable a cutter bit (not shown) held in the router 11 to engage with the workpiece. The platen 12 is itself carried by a carriage 14 on the jig 10 by means of a slidable connection, here in the form of an extruded dovetail section 15. The position of the platen 12 relative to the carriage 14 can be adjusted along a vertical axis y (see Figure 1) and held in place by a releasable clamping bolt 16 (see Figure 4).

The carriage 14 is itself mounted for slidable movement relative to the jig 10 in two orthogonal horizontal axes x and z (See Figure 1), as will be explained in more detail below.

The jig 10 is itself designed to be mountable to a table or work bench. For this purpose, the jig 10 has two arms 17a, 17b which can be anchored by suitable means such as bolts 18a, 18b. Ideally, the jig 10 can be mounted on one of the jaws of a portable work bench (preferably the fixed jaw). This conveniently enables the router 11 to be deployed on work pieces held in the jaws (50, 51) of the work bench (see Figure 3).

Figure 3 illustrates a key feature of the jig 10, namely that it enables the router 11 to be swung out of the way into an inoperative position.

This is convenient in particular for allowing easy access to the jaws 50, 51 of the work bench for setting the workpiece in position. It may also facilitate changing over cutter bits in the router 11.

The platen mounting arrangement comprises an elongate rod 20 and an elongate bar 21 that are each fixed at right angles to the platen 12 and extend in parallel therefrom. The rod 20 is of circular cross-section and is slidably held within an elongate guide sleeve 22. The bar 21 is of square cross-section and is slidably held by a bracket 23. Both the bracket 23 and guide sleeve 22 are fixed to a yoke piece 24. This arrangement ensures that the platen 12 is guided for reciprocable movement along the z axis (Figure 1). The bracket 23 incorporates a releasable locking bolt 26 to clamp the bar 21 and thus enable the platen 12 to be held in a fixed position along the z axis, if desired. The bar 21 additionally incorporates adjustable end stops 27, 28 to act to limit the reciprocal movement of the platen 12 along the z axis.

The yoke piece 24 is itself in the form of an elongate guide sleeve and is mounted on a round-section rod 29 that extends between the two arms 17a, 17b of the jig 10 parallel to the x axis (see Figure 1). The yoke piece 24 is slidable along the rod 29. It will be noted that the arrangement also enables the yoke piece 24 to rotate about the rod 29. This enables the platen 12 to be swung between an operative position where the router 11 can engage a workpiece (seen in Figure 2) and an inoperative position where the router is disengaged from the workpiece, eg for setting up a new workpiece and/or changing a cutter bit (seen in Figure 3).

The platen 12 is deployed in its operative position by means of a bracket 30 fixed on the guide sleeve 22. The bracket 30 is engagable with a

bar 31 extending between the two arms 17a, 17b parallel to the x axis. The bracket 30 incorporates a slidable latch 32. When the platen 12 is swung into its operative position, the bracket 30 will engage the bar 31 and if the latch 32 is slid over the bar 31, this will stop the platen swinging back out of position. The bracket 30 has a releasable locking bolt 33 for clamping to the bar 31. If the locking bolt 33 is clamped down hard on the bar 31, this will hold the platen 12 in its operative position, but also prevent its movement along the x axis. If it is desired to enable the platen 12 to move along the x axis, the locking bolt 33 must be released sufficiently to allow the bracket 30 to slide along the bar 31. In use of the router 11, downward pressure on the router applied by the user will ensure that the bracket 30 remains in contact with the bar 31. The rod 29 and bar 31 together ensure that the platen 12 is guided for reciprocable movement along the x axis. The bar 31 further incorporates adjustable end stops 34, 35 to act to limit the reciprocal movement of the platen 12 along the x axis.

The jig 10 includes a facility for allowing the router 11 to make cuts to a set pattern. This takes the form of a pin 40 mounted on the carriage 14 which is engagable with a template 41. The template 41 is held in a fixed position relative to the jig 10 by means of a holding tray 43 which is bolted to one or other of the arms 17a, 17b. The pin 40 is mounted on the carriage 14 by means of a slotted bracket 42 to enable the position of the pin along the z axis to be adjusted to suit the workpiece set-up. This allows the possibility for the cutter bit of the router to be applied to the centre of the workpiece, for example when making mortice and tenon joints. The arrangement enables suitable adjustments to be made for different thicknesses of workpiece. With the pin 40 following the contours of the template 41, the router 11 will be guided to produce appropriate cuts in the workpiece. Different templates may be provided for producing different cutting patterns, such as dovetail joints, for example, or lettering.

It will be noted that the pattern cutting facility in this jig is arranged to be at one side of the router. In conventional pattern cutting arrangements, the template for the router to follow is typically situated beneath the router itself. The arrangement in the jig shown here is easier to use than these conventional arrangements and hence more reliably produces satisfactory results.

The various components from which jig is made can be of any suitable material, eg lightweight metal. However, it is preferred to use extruded sections where possible, as this is less expensive to produce than cast components. It is important to try to ensure smooth and accurate movement of the router along the x and z axes. Free running is especially important when the router is extended fully out along the z axis. This is achieved in the jig described above by providing that the rods 20 and 29 are of hardened and ground steel, with the guide sleeve 22 and yoke piece 24 incorporating linear ball races.

The bars 21 and 31 essentially serve to prevent rotation around the rods. There is no need for such a high degree of accuracy, so it is acceptable to use bar material for these, rather than rod. It is important that the sliding contact of the bars is as friction free as possible, however, so the brackets 23 and 30 are provided here with a low friction material, eg Acetal pads, for the sliding contact surfaces with the bars. Another advantage of using bar material is that the clamping bolts on the brackets and on the end stops tend to work better than with rod, where there is a tendency for the bolts to rotate and dangle when released.

In use, the jig will ideally be bolted to the fixed jaw of a portable work bench. The workpiece can be positioned in the jaws whilst the router is in its inoperative position (Figure 3). If a detailed joint is to be made, the chosen template is fixed in position. The router can now be swung into its

operative position and the latch slid into position to hold it there. The position of the pin on the carriage is now adjusted along the z axis relative to the template to suit the workpiece. The height of the router along the y axis is also adjusted. The router is now ready to perform the patterned cuts in the workpiece. The router is brought into final cutting engagement with the workpiece (along the y axis) using the plunge facility in the router itself.

It will be appreciated that the jig described above enables the router to be manoeuvred with certainty along x and z axes, enabling a user to make cuts in even very small or thin workpieces - something that is normally very difficult to achieve with a tool of this kind.

As seen in Figure 5, the jig also enables the router to be used in the manner of a routing table. The router 11 is deployed in its operative position and fixed with respect to x, y and z axes using the clamping bolt 16 on the carriage 14 and the clamping bolts 26 and 33 on brackets 23 and 30 respectively. A block of wood 60 is clamped between the jaws 50, 51 of the work bench to form a fence. Workpieces can now be fed past the cutter bit 61, guided by the block of wood 60 acting as a fence. The ability of the jig to allow the router to be used in this way greatly adds to its versatility.

The modified jig seen in Figures 6 to 9 differs from the jig seen in Figures 1 to 5 in terms of various design details, although its basic functionality remains the same. Thus, for example, the bar 31' of the modified jig performs the same role as the bar 31 of the Figure 1 jig, but its position has been changed. This simplifies the design of the two arms 17a', 17b' upon which it is mounted. Also, the bar 31' is now located forward of the rod 29', whereas the bar 31 and rod 29 are the other way round in the Figure 1 jig. Movement of the carriage 14' in the modified jig is guided by the rod 29' and bar 31' along the x axis in analogous manner to the movement of the carriage 14 in the Figure 1 jig.

For movement of the carriage 14' along the z axis, the modified jig incorporates two rods 20a', 20b', one on either side of a bar 21'. Although this adds to the overall cost of the jig, its strength and stability is enhanced.

As with the Figure 1 jig, the platen 12' of the modified jig can be swung about the rod 29' into an inoperative position (see Figure 8) for changing the cutter bit and/or setting up a new workpiece.

The design of the platen 12' has been changed in the modified jig, by incorporation of a pair of opposing clamps 70. This gives the jig greater freedom to accomodate different shapes and sizes of cutting tool and simplifies the process of mounting such tools on the jig. Cutting tools can be mounted on the jig simply by clamping their lower flange onto the platen 12' between the clamps 70. It will also be noted that the pin 40' to engage the template 41 (for dovetail jointing etc) is now conveniently mounted directly onto a boss 71 on the platen 12'.

Another significant improvement in the modified jig is the introduction of a workpiece locating device 80. This is seen in more detail in

Figure 9. As will be seen, the device 80 is in the form of a bracket which can be clamped by a bolt 81 to one of the jaws of the work bench (preferably the fixed jaw 50). The bracket comprises a first datum surface 82 which extends at right angles to the edge of the work bench jaw 50 and lies in the plane of the z-axis. The bracket further comprises a bifurcated second datum surface

83a, 83b which extends above and below and flush with the work bench jaw

50 and lies in the x-axis. In use, a workpiece is clamped between the jaws of the workbench after a corner of the workpiece has been brought up to the two datum surfaces 82 and 83a, 83b. This ensures that the workpiece is square to the axes of movement of the cutting tool and that it remains so during the cutting process.

It will further be noted that the workpiece locating device 80 also acts as the means for mounting the template holding tray 43. The device 80 has a bracket 84 for this purpose, the bracket being attached to the device via an adjustable rod 85. This arrangement ensures the correct alignment of a workpiece with respect to the template 41 when the workpiece is correctly located between the datum surfaces 82 and 83a, 83b of the locating device 80.