GB2123338A - Apparatus and method for cutting a mortice - Google Patents

Abstract

A morticing jig includes a pair of guide rods 1A, 1B fitted with clamps 2A, 2B and 2A%, 2B% by which the apparatus can be mounted temporarily to the edge of a door D (Figure 2). A carrier 8 mounted between slides 7A, 7B on the rods 1A, 1B bears a rotary cutting tool 12 through a bearing 9. The cutter is traversed along the door edge to cut the mortice by sliding movement of the carrier. The carrier is articulated to the slides 7A, 7B by pin joints 11A, 11B so as to maintain the bearing 9 centred between rods 1A, 1B irrespective of the spacing of the latter, so that the cutter 12 always acts in the medial plane of the door irrespective of the door thickness. <IMAGE>

Description

SPECIFICATION Apparatus and method for cutting a mortice The present invention relates to apparatus for use in cutting a mortice, and in particular for cutting a mortice in a door edge to receive a lock, (which term is also to be regarded herein as embracing a latch or other like fastening device).

It is well known that the strength and effectiveness of a mortice lock installation very much depends on the accurate alignment of the cut mortice with the medial plane of the respective door, and the general closeness of fit between the mortice and the case of the lock. To cut an accurately aligned and sized mortice in an existing door using only ordinary hand tools (for example by the common procedure of boring a row of separate holes in the door edge and then paring away remaining wood with a chisel) is both time consuming and requires considerable skill. The exercise can be greatly facilitated, however, through use of a jig clamped to the door and arranged to guide an appropriate cutting tool along the door edge following the required line of cut.Any such apparatus should most desirably establish the correct alignment of the cutting tool with the medial plane of the door automatically and for a useful range of different door thicknesses. Jigs of this nature are disclosed in United Kingdom patent specification No. 1450020 and published patent application No. 2075911 A. While these earlier forms of apparatus can in general perform quite successfully in cutting a required mortice they are relatively complex and costly to manufacture, and can be cumbersome to handle. It is an object of the present invention, therefore, to provide an apparatus suitable for use in guiding a cutting tool for the purposes indicated above which is of simple construction and economic to manufacture, as well as accurate and easy to use.

In accordance with one aspect of the invention apparatus for use in cutting a mortice comprises a pair of generally parallel guides; at least one pair of opposed clamps connected to respective said guides; means for driving said pairs of clamps and guides towards and away from one another, where by said clamps can be clamped to the opposite faces of doors or the like workpieces of a thickness within a predetermined range with said guides extending parallel to the workpiece edge and spaced apart by a dimension which varies with the workpiece thick ness; a pair of slide means borne for movement along respective said guides; and a carrier provided with bearing means to support a cutting tool, which carrier is connected between said slide means by articulated linkages such that said bearing means can be traversed along a rectilinear path parallel to the workpiece edge by movement of the slide means along said guides when clamped as aforesaid, and said bearing means remain spaced medially between said guides irrespective of the said dimension by which the guides are spaced apart.

The invention also resides per se in a method of cutting a mortice in the edge of a door or the like workpiece which comprises the steps of taking an apparatus in accordance with the above defined first aspect of the invention, clamping the clamps of the or each said pair thereof to the opposite faces of the workpiece with said guides extending parallel to the workpiece edge; and traversing a cutting tool supported by said bearing means along a rectilinear path parallel to the workpiece edge and in the medial plane of the workpiece by movement of said slide means along said guides.

Although the apparatus provided by the invention is designed for use in cutting mortices where movement of the cutting tool along, as well as into, the workpiece edge is required, the same apparatus can of course also be used if desired in preparing bores at selected locations on a workpiece edge where no traverse movement of the drill or like tool which the apparatus bears is required during actual cutting.

These and other aspects of the present invention will now be more particularly described, by way of example, with reference to the accompanying drawings, in which: Figure 1 is a front view of a preferred embodiment of portable morticing jig made in accordance with the invention; and Figure 2 is a bottom plan view of the jig of Figure 1 as fitted with a cutting tool and applied to a door.

Referring to the drawings, the illustrated appar Mus includes a pair of generally parallel guide rods 1 A, 1 B to the lower ends of which are fixed a pair of opposed clamps 2A, 28. A shaft 3 passes through a plain bore in clamp 2A and a screw thread 3A on the end of the shaft mates with a tapped bore in the clamp 2B, while a compression spring 4 urges the clamps and guide rods apart so that clamp 2A abuts a cross-pin 5 on the shaft 3. Rotating the shaft 3 by means of a thumb turn 6 therefore either drives the clamps and guide rods closer together against the force of the spring 4 or allows the clamps and guide rods to move further apart in accordance with the bias of the spring, depending upon the sense in which the shaft 3 is turned.

Towards the opposite end of the rods 1 A, 18 a second clamping assembly comprising clamps 2A', 2B', shaft 3', spring 4', pin 5' and turn 6' is provided, this being identical to the lower clamping assembly just described except that the upper clamps are not fixed in position with respect to their respective guide rods but are allowed to slide axially along the rods.

Also slidable along the respective rods 1A, 18 are a pair of brackets 7A, 7B and between these brackets a tool carrier 8 is mounted. In the centre of the carrier 8 a bearing 9 is provided to serve as an axial guide for a rotary cutter shaft 10, the axis of this bearing being perpendicular to the longitudinal axis of the rods 1 A, 1 B. The mounting of the carrier 8 to the brackets 7A, 7B is by means of respective pivot pins 1 A, 11 Bat the opposite ends of the carrier, and by this means it is ensured that whatever the lateral spacing between the two guide rods 1A and 18 the axis of the bearing 9 always remains centred between them.For example, if the spacing between the rods 1A, 18 is reduced from that shown in Figure 1 (by tightening the clamp screws 3, 3') the brackets 7A and 7B are constrained to slide respectively downwards and upwards on their guide rods as the carrier 8 rotates anticlockwise as viewed (about the axis of the bearing 9), with the pivot pins 1 1A, 11 B following the paths of the arrows "A". Conversely, the tendency of increased spacing between the rods 1A and 1 B is to rotate the carrier anticlockwise as viewed, sliding the brackets 7A and 7B in the opposite senses.

In use of the illustrated jig to cut a mortice in a door edge, a routing cutter bit 12 ofselected diameter corresponding to the desired mortice width is first fixed to the end of the shaft 10 and the latter is then fed through the bearing 9 (from its lower side as viewed in Figure 2). The pairs of clamps 2A, 2B and 2A', 2B' are set apart so as to embrace the opposite faces of the door and the jig is presented to the door edge with the guide rods 1A, 18 parallel thereto and the cutter bit 12 forward. The clamps are then tightened to fix the jig to the door D as shown in Figure 2. By virtue of the articulated linkage between the carrier 8 and brackets 7A, 7B as described above the axis of the bearing 9 and cutter 12 now automatically lies in the medial plane of the door D, whatever its thickness.

The end of the shaft 10 opposite to the cutter 12 is reduced in diameter to fit a standard portable drill chuck 13. To cut the mortice the drill is operated and the cutter 12 fed into the door edge, being guided in this respect by the shaft 10 passing through the bearing 9. The assembly of carrier 8 and brackets 7A, 7B is then slid by hand along the rods 1 A, 18 to guide the cutter 12 along a rectilinear path in the medial plane of the door, to cut the required length of mortice. Preferably the tool is used in a series of passes taking successive "bites" of material to form the mortice, the total depth of which can be set by an adjustable stop collar 14 fitted over the shaft 10 after the latter is mounted in the bearing 9. To set the vertical extent and position of the mortice cut the clamping assemblies can themselves be used as end stops for the movement of the carrier 8, in conjunction with the brackets 7A, 7B. That is to say the jig is positioned on the door so that with the bracket 7A resting on the clamp 2A the cutter 12 lies at a position corresponding to the lower edge of the required mortice, and the upper clamp assembly is slid down on the guide rods prior to final tightening so that the clamp 2B' stops the upward movement of the carrier 8 by abutment with bracket 7B when the cutter 12 is at a position corresponding to the upper edge of the required mortice. Alternatively, separate adjustable stop collars could be provided on the rods 1A, 18 if desired.

Claims (8)

1. Apparatus for use in cutting a mortice comprising a pair of generally parallel guides; at least one pair of opposed clamps connected to respective said guides; means for driving said pairs of clamps and guides towards and away from one another, whereby said clamps can be clamped to the opposite faces of doors or the like workpieces of a thickness within a predetermined range with said guides extending parallel to the workpiece edge and spaced apart by a dimension which varies with the workpiece thickness; a pair of slide means borne for movement along respective said guides; and a carrier provided with bearing means to support a cutting tool, which carrier is connected between said slide means by articulated linkages such that said bearing means can be traversed along a rectilinear path parallel to the workpiece edge by movement of the slide means along said guides when clamped as aforesaid, and said bearing means remain spaced medially between said guides irrespective of the said dimension by which the guides are spaced apart.

2. Apparatus according to claim 1 wherein there are two pairs of said clamps connected to said guides, at axial locations to either side of said carrier and slide means.

3. Apparatus according to claim 1 or 2 wherein the axial location of at least one pair of said clamps is adjustable along said guides.

4. Apparatus according to any preceding claim wherein said carrier is connected to each said slide means by a respective pin joint the axis of which is perpendicular to the longitudinal axes of said guides.

5. Apparatus according to claim 4 wherein each said pin joint is provided on the respective slide means at a location to the side of the respective guide remote from the other guide.

6. Apparatus according to any preceding claim wherein a said driving means for a said pair of clamps comprises a rotatable shaft passing through a first said clamp and screwthreadedly engaged with the second said clamp in the pair, with spring means biasing said clamps apart and so that said first clamp engages an abutment fast with the shaft to that side of the first clamp remote from the second clamp.

7. Apparatus for use in cutting a mortice substantially as hereinbefore described with reference to the accompanying drawings.

8. A method of cutting a mortice in the edge of a door or the like workpiece which comprises the steps of taking an apparatus in accordance with any preceding claim, clamping the clamps of the or each said pair thereof to the opposite faces of the workpiece with said guides extending parallel to the workpiece edge; and traversing a cutting tool supported by said bearing means along a rectilinear path parallel to the workpiece edge and in the medial plane of the workpiece by movement of said slide means along said guides.