GB2298161A - Circular groove/hole cutting attachment for routers - Google Patents

Abstract

An attachment for fixing to a router base includes a serrated component 1 which carries a pivot 4 in a short slot. The component 1 is rotatable about screw 6. A locking segment 3 engages serrated member 1 and retains it in position to determine the radius between the router cutter and the pivot 4. The radius can be finely adjusted by movement of the pivot 4 in its slot.

Description

CIRCULAR GROOVE/HOLE CUTTING ATTACHMENT uVn/HOLi WOTTING ATTACnMLNT FOR ROUTERS This invention relates to a cutting attachment fitted to the base of a Router for the purpose of cutting circular grooves and/or holes.

Used extensively in woodworking the Router can be used to cut circular grooves and/or holes providing some attachment such as a trammel or compass device is used to guide the Router.

Trammels or Compass devices are by necessity large and do not allow circular cuts to be made smaller than the Router itself.

The present invention is secured to the base of the Router to provide a smooth working surface and also by means of an adjustable pivot allows the Router to be rotated at an infinitely variable radius selected within the physical limits of the attachment.

The shape of a Router base to which the attachment is fitted varies with the design determined by the Router manufacturer. Some designs have tapped securing holes to which are fitted a plastic smooth base plate.

The present invention refers to kouters where such securing holes already exist or where securing holes may be conventiently drilled and tapped.

Two specific embodiments of the invention are described by way of example with reference to the accompanying drawings.

Figure 1/3 shows the profile of a Router Base where four screws item 6 are used to secure a plastic working surface comprising a fixed piece item 2, an adjustable toothed pivot holder item 1, and a locking segment item 3.

The pivot. item 4 is secured to item 1.

Figure 2/3 shows the profile of a Router Base where three screws item 6 are used to secure a plastic working surface comprising an adjustable toothed pivot holder item 1 and a locking segment item 2, The pivot item 4 is secured to item 1 and is shown at a minimum distance from the Router Cutter.

Figure 3/3 shows the attachment as described in Figure 2/3 but with the pivot item 4 extended to a maximum distance from the Router Cutter.

Figure 3/3 shows an elongated slot which by slackening the screw item.6 permits the locking segment item 2 to be engaged or disengaged with the serrated teeth of item 1.

Referring to the drawings the attachment comprises a number of plastic or metallic plates of sufficient thickness to allow the countersunk head screws item 6 to secure the component plates in position without the screws protruding above the plate surface.

Referring to Figure 1, item 1 may be rotated through 1600 and locked in position by the locking segment item 3. Temporary slackening of the screws items 6 and 5 allow the setting of the pivot item 4 to be positioned at the required distance from the cutter.

if a clockwise rotation of the Router is envisaged the tooth on the locking segment, item 3 corresponding with the letter R must be engaged with the pivot holder item 1. Similarly if a counter clockwise rotation of the Router is envisaged the tooth corresponding with the letter L on the locking segment must be engaged with the pivot holder item 1.

In both the aforementioned locking positions it is an essential feature that the teeth of the locking segment item 3 are set at a distance from the retaining screw 6, greater than the minimum distance from the screw 6 to the nearest tooth on the pivot holder item 1.

Item 4 comprises of a Nylon pivot but may be of any other suitable material and should be approximately 12mm dia. The purpose of the pivot is to allow the Router to be rotated in an arc around the pivot so that the cutter may cut a groove of a corresponding radius controlled by the position of the pivot relative to the cutter.

Fine adjustment of the chosen radius is obtained by sliding the pivot in the elongated slot and locking by means of tne set screw item 5 Figure 2, thus enabling an infinite variation of circular cut to be made between the range of maximum and minimum setting.

Claims (5)

1. An attachment comprising thin plastic (or other rigid materialj flat pieces which are secured to the base of a Router as used for example in woodwurking.

2. One piece of the attachment as claimed in Claim 1 is serrated and contains a pivot housed in an elongated slot.

3. The rotation of the serrated piece as claimed in Claim 2 is locked in position by a segmented piece which engages with the serrated piece as described in Claim 2.

4. In addition to the pieces described in Claims 2 & 3 a third piece may be included in the invention to provice maximum bearing surfac8.

Such a piece would depend on the design of the Router so chosen.

5. A circular groove/hole cutting attachment for Routers substantially as described herein with reference to Figures 1-3 of the accomDanying drawing.