GB2208624A

GB2208624A - Mitre cutting cramp

Info

Publication number: GB2208624A
Application number: GB8718948A
Authority: GB
Inventors: Alan Cunnick
Original assignee: Individual
Current assignee: Individual
Priority date: 1987-08-11
Filing date: 1987-08-11
Publication date: 1989-04-12
Anticipated expiration: 2007-08-11
Also published as: GB2208624B; GB8718948D0

Abstract

The cramp comprises a workpiece supporting table 3 for supporting a pair of workpieces 25,27. Mounted to table 3 are a pair of adjustable workpiece-engaging fences 7,9 which can be set spaced apart at a predetermined relative angle corresponding to the desired included angle of a mitred corner. At least one clamp 17,19,23 is provided to clamp a workpiece against a respective fence. A cutting guide 31 is provided for guiding a cutting tool (eg. a handsaw or circular saw) along an elongate cut line traversing the space between the ends of fences 7,9. The cutting guide is mounted above the table so that it overlies at least one of the workpieces. The workpieces can be set at any desired relative angle, even at an angle of 180 degrees for producing butt joints. Guide elements 33 of the cutting guide can be swung away to allow the cramp to be used for gluing or nailing operations. A removable panel (not shown) can be secured in cut-out portion 12 when the cramp is intended for left-handed cutting operation with a workpiece along face 10 of fence 7. <IMAGE>

Description

Mitre Cutting Cramps The present invention is concerned with cramps for positioning elongate workpieces so that they can be cut to form mitred ends, for purposes such as assisting in the construction of picture frames and of joints between architraves, pipes and tubes and the like.

A number of such cramps are available which enable two lengths of workpiece to be cut to form the mitred ends which will be joined together. Although there is usually a guide for guiding the cutting tool (for example, a saw), it is possible for the cutting tool to be slightly out of alignment so that, for example, it does not cut absolutely vertically. Because each workpiece is generally cut independently, the two mitred ends may not fit together perfectly.

My prior patent application number 8701386 (Specification number 2185436) describes a cramp which permits two workpieces to be cut simultaneously in such a way that any error in the alignment in cutting one workpiece is compensated by a corresponding error in the reverse sense in cutting the other workpiece.

The mitre cutting cramp disclosed in the above-mentioned patent application comprises: a pair of workpiece-supporting surfaces; a corresponding pair of workpiece-engaging surfaces, each of which is upstanding relative to a respective one of said workpiece-supporting surfaces, said workpiece-engaging surfaces being arranged to be set, spaced apart, at a predetermined -relative angle corresponding to the included angle of a mitred corner; at least one clamping member arranged to clamp a respective workpiece against a corresponding workpiece-engaging surface; a cutting guide for guiding a cutting member along an elongate cut line traversing the space between the ends of said workpiece-engaging surfaces, said ends being spaced at the points where they intersect said line.

The cramp described in the above-mentioned specification allows the two workpieces to overlap in the region of the space between the workpiece-engaging surfaces, so that the required mitred ends can be cut on both workpieces at the same time. If the cutting member is held at a slight angle to the desired line of cut, this angle would be common to both workpieces so that they will still fit together exactly.

Various embodiments of mitre cutting cramps are described in the above-mentioned patent specification. In each case the cutting guide is located at the level of the workpiece-supporting surfaces and comprises elements either extending upwardly therefrom. In each case guide elements are located adjacent the desired line of cutting the workpiece, at spaced apart positions.

According to the present invention there is provided a mitre cutting cramp which comprises: a pair of workpiece-supporting surfaces; a corresponding pair of workpiece-engaging surfaces, each of which is upstanding relative to a respective one of said workpiece-supporting surfaces, said workpiece-engaging surfaces being arranged to be set, spaced apart, at a predetermined relative angle corresponding to the desired included angle of a mitred corner; at least one clamping member arranged to clamp a respective workpiece against a corresponding workpiece-engaging surface; a cutting guide for guiding a member along an elongate cut line traversing the space between the ends of said workpiece-engaging surfaces, said ends being spaced at the points where they intersect said line;; said cutting guide being mounted above the workpiece-supporting surface so that, in use, the workpieces will lie below the cutting guide.

Preferably the guide is formed from two elongated guide elements mounted in side by side relationship to provide a channel for guiding the cutting member. The guide elements generally have parallel faces which are substantially perpendicular to the workpiece supporting surface. The parallel faces are preferably closer together than the "set" of the teeth of the saw so that, in use, they prevent the saw being withdrawn in any direction other than the longitudinal direction of the guide elements.

Preferably the guide extends substantially horizontally from a position located above the space between the ends of the workpiece-engaging surfaces to a position located above the peripheral edge of the cramp. More preferably the guide is mounted at one end of a member or members providing at least one of said workpiece-supporting surfaces and at the other end to a support member located at or near the peripheral edge of the cramp. The support member may be in the form of a vertical post which preferably provides a vertical guide element cooperating with the horizontally arranged elevated guide elements. This vertical guide element may be provided by a slot extending substantially the length of the post.

A mitre cutting cramp in accordance with the present invention enables cutting members with much shorter blades to be used than those required for the cramps described in the above-mentioned patent application. This is because the guide, although formed of elongate elements, extends only in one direction from a region in which the ends of the workpiece-engaging elements lie.

Furthermore the side by side guide elements may be mounted relatively close together since it is only necessary that they accommodate that part of the blade of a cutting member such as a saw at a position above the saw teeth, where the blade is narrower than the region where the saw teeth lie. Accordingly the cutting member is held, during use, against any significant movement away from the line of intended cut.

One or both of the guide elements may be pivotally mounted about a vertical axis so as to permit easier access for the cutting blade. When the guide element is pivotable in this sense, means is preferably provided to secure the guide element in position for the cutting operation.

The horizontally aligned guide elements may be of a depth sufficient to prevent any significant turning of the blade of the cutting member about a horizontal axis. In addition, the provision of a cooperating vertically aligned guide member will help prevent any such movement of the blade cutting member.

An illustrative embodiment of the present invention will now be described by way of example only with reference to the accompanying drawing, which is a perspective view of a mitre cutting cramp.

Referring to the accompanying drawing, the mitre cutting cramp illustrated comprises a substantially circular support table 1 to which is bolted upper support table 3 which is also of substantially circular shape but of somewhat smaller radius than that of support table 1. Tables 1 and 3 are shaped so as to provide a clearance therebetween around at least an edge portion of the underside of table 3.

Extending upwardly from the centre of upper table 3 is a post 5 to which are connected for pivotal movement thereabout a pair of workpiece-engaging fences 7,9. Each fence extends from central post 5 to a position beyond the periphery of the lower table 1. Between the periphery of upper table 3 and lower table 1 each fence has a downwardly extending extension 11 which itself is shaped so as to extend at least some distance into the clearance space between the upper table 3 and the lower table 1. Accordingly, each fence 7,9 is held captive on upper table 3 but is free to move over the surface of the upper table around the post 5.Each fence 7,9 is provided with a rod 13 having a smooth unthreaded portion terminating above the fence with a knurled knob 15 and a threaded end extending through a bore extending the entire vertical length of the fence. Rnob 15 may be turned to cause the threaded end of the rod 13 to engage or disengage from the upper surface of upper table 3 thereby clamping or unclamping a fence in a desired position.

Each fence 7,9 is also provided with a projection 17 extending vertically from the upper surface of the fence.

Projection 17 is provided with a horizontal throughbore for accommodating a rod 19 extending through the bore and to each side of the fence. Rod 19 may be clamped in a desired position within the bore of projection 17 by means of a clamping screw 21 located in a screw threaded bore also extending into projection 17.

Fixedly located on each rod 19 is an elongate square section block 23 which extends downwardy from rod 19 to the upper surface of upper table 3 on one side of fence 7,9.

This arrangement of projection 17, rod 19, screw 21 and block 23 provides, together with fence 7,9, a clamp enabling a workpiece 25,27 to be firmly held in position against a side of a fence 7,9 and lie on the upper surface of upper table 3, as illustrated in the drawing.

The workpiece-engaging face 8 of fence 7 is preferably substantially flat; the other face 10 thereof as illustrated has a cut-out portion 12 which provides space for waste from the end of workpiece 27. It is particularly preferred that the corresponding face of fence 9 has a similar cut-out portion (not shown) which is normally covered with a removable panel with an outer face flush with the face of fence 9; this removable panel may be secured in cut-out portion 12 when the cramp is intended for left-handed operation with a workpiece along face 10 and the end thereof in the cut-out portion of fence 9.

Extending along a diameter of upper table 3 is a relatively wide groove 29 which passes under central post 5 and which will lie under the line of cut when the cramp is in use.

In order to maintain the blade of the cutting member along the line of cut, a cutting guide 31 is provided. Guide 31 comprises two side by side elongate elements 33, each comprising elongate base portion 35 and upstanding flange 37 providing one of the guide surfaces. Each flange 37 is straight over most of its length but has curved ends 39,40 allowing for easy entry of the blade of the cutting member.

The guide elements 33 are each mounted at one end to central post 5 by means of screw 2 and at the other end to edge support post 41 by means of screw 4. These screws are removable such that the guide elements may be pivotted away from the parallel arrangement. (They may for example be swung right away if the cramp is to be used for gluing or nailing, or other jointing operations.) Support post 41 is itself mounted on an edge portion of lower support table 1.

Central posts 5 and edge support post 41 are each provided with vertically extending slots 43,45 which are aligned with the elevated guide 31 and the centre of groove 29. One or both the slots 43,45 may be of substantially the same width as the guide 31, so as to cooperate therewith in particular to prevent natural movement of the lower part of the blade of the cutting member when the device is in use.

Alternatively one or both the slots 43 may be substantially wider than guide 31, in which case the maintenance of the saw blade in this desired position is effected substantially entirely by guide 31.

Figure 1 illustrates the position after the cramp has been used with the workpieces still in position. Prior to cutting, each workpiece will extend beyond the cutting line located centrally over groove 29. A cutting tool (for example a bandsaw or motor driven circular saw) is introduced through slot 43 and post 41 so that the cutting blade lies partly within guide 31 and extends through slot 43 and post 5. The ends of the workpieces 25,27 are then cut.

In most respects the cramp in accordance with the present invention, and its use, is essentially as described in my above mentioned earlier patent application.

The above-described cramp can be made of any suitable material or combinations of material and may be used for cutting workpieces made of various materials, for instance, wood, metal or plastics.

The present invention has been described with reference to a cramp for cutting mitred corners. Mitred corners can be created at any desired angle for use in a cramp according to the invention, even with the workpieces at an angle of 180t. the resulting joints between workpieces at an angle of 180t will generally be referred to as butt joints when the cut line is perpendicular to the workpieces, and scarf joints when the cut line is at an acute angle to the workpieces.

Claims

Claims:

1. A mitre cutting cramp which comprises: a pair of workpiece-supporting surfaces; a corresponding pair of workpiece-engaging surfaces, each of which is upstanding relative to a respective one of said workpiece-supporting surfaces, said workpiece-engaging surfaces being arranged to be set, spaced apart, at a predetermined relative angle corresponding to the desired included angle of a mitred corner; at least one clamping member arranged to clamp a respective workpiece against a corresponding workpiece-engaging surface; a cutting guide for guiding a member along an elongate cut line traversing the space between the ends of said workpiece-engaging surfaces, said ends being spaced at the points where they intersect said line; said cutting guide being mounted above the workpiece-supporting surface so that, in use, the workpieces will lie below the cutting guide.

2. A mitre cutting cramp according to claim 1, wherein said guide extends substantially parallel to said workpiece-supporting surfaces from a location above said space to a location adjacent the peripheral edge of said cramp.

3. A mitre cutting cramp according to claim 1 or 2, wherein said guide comprises a pair of elongate guide elements mounted in side-by-side relationship so as to define a channel between said guide elements for guiding said cutting member.

4. A mitre cutting cramp according to claim 3, wherein said guide elements have substantially parallel facing surfaces substantially perpendicular to said workpiece-supporting surface.

5. A mitre cutting cramp according to claim 3 or 4, wherein one end of each of said guide elements is mounted at one end of a respective member providing said workpiece-supporting surface, the other end of each of said guide elements being mounted to an upstanding member located adjacent the peripheral edge of the cramp.

6. A mitre cutting cramp according to claim 5, wherein each said upstanding member comprises a post disposed substantially perpendicular to said workpiece-supporting surfaces, said posts defining a slot therebetween.

7. A mitre cutting cramp according to any of claims 2 to 6, wherein at least one of said guide elements is pivotally mounted about an axis substantially perpendicular to a respective workpiece-supporting surface.

8. A mitre cutting cramp according to claim 7, further comprising means for selectively securing said pivotal guide element against pivotting.

9. A mitre cutting cramp, substantially as described herein with reference to the accompanying drawing.