WO2002011950A1

WO2002011950A1 - Joint forming tool

Info

Publication number: WO2002011950A1
Application number: PCT/GB2001/003443
Authority: WO
Inventors: Bernard Cartwright
Original assignee: Bernard Cartwright
Priority date: 2000-08-03
Filing date: 2001-08-03
Publication date: 2002-02-14
Also published as: GB0018924D0; EP1307322A1; AU2001276480A1

Abstract

A joint forming tool is provided for facilitating the formation of butt joints and T-joints between sheet materials. The tool comprises an angle bracket (1), a base member comprising a base plate (2) and top plate (3) of identical configurations, a first resiliently biased clamping surface formed by a first clamping jaw (4) and a second resiliently biased clamping surface formed by a second clamping jaw (5). Gaps formed between inner most parts of the first and second clamping services and the angled bracket are arranged to receive first and second pieces of sheet material to be joined to one another in a butt joint. The first piece of sheet material is inserted a first gap and the second piece of sheet material is inserted a first gap. The tool is arranged such that the first and second sheets are held in an ideal configuration in which the two pieces of sheet material may be joined to one another by gluing or, for instance, screwing.

Description

Joint Forming Tool

The invention relates to a joint forming tool.

Specifically, the invention relates to a tool for facilitating the formation of butt joints and T-joints between sheet materials.

In order to make a butt joint or a T-joint, glue and/or a mechanical means of fastening must be applied to the areas to be joined together, then the sheets of material to be joined need to be offered up to one another and held together while the glue dries, and/or while fixings are put into place. In practice, anyone who has ever tried to butt joint large sheets of MDF, plywood, chipboard etc., will know the frustration of trying to hold the sheets at exactly 90° to one another, line up top, bottom and sides, and hold them steady whilst tightening a long sash cramp. In glued joints, the glue between the two surfaces also tends to act as a lubricant in its wet state and causes the sheets to slide, more so as the final turn to the cramp is given.

Referring to Figures 1 and 2, two traditional tools and methods are shown for clamping sheets of material at 90° to one another.

Considering firstly Figure 1, a pair of vices 1, 2 are arranged at 90° to one another and mounted upon a base plate 3. The sheet materials to be joined to one another are placed against a non-moving plate 4, 5 of the vices 1, 2 and the moving jaw 6, 7 of the vices is screwed shut so as to clamp the sheet material between jaws 6, 4 and 5, 7. Whilst this method enables safe and secure handling of sheet materials, it will be appreciated that the vice arrangement and mounting board etc. is a rather large and unwieldy one and is not something which could be regarded as terribly useful to a mobile carpenter or keen DIY enthusiast.

Referring now to Figure 2, there is shown a second arrangement which uses a variation of the technique shown in Figure 1. In Figure 2, a single moving element is provided having a right-angled bracket 8 which moves in an axis equidistant between axes of a pair of static plates

9, 10 arranged at 90° to one another. With the angle bracket 8 moving along the 45° axis between the two static plates 9, 10 the bracket 8 can be used to sandwich sheet material between its two faces 81, 82 and the static walls

10, 9 respectively. Even though this arrangement has only one moving element, it is still a rather bulky configuration and, again, requires steady mounting of all the pieces on a baseboard. Further, because of the way in which the angle bracket 8 moves, if the two sheets of material to be butted to one another are of significantly different thicknesses, the clamp will only securely hold the thicker of the two materials, and the thinner one is left to float freely.

It is an aim of preferred embodiments of the present invention to provide a simplified joint forming tool to provide a "semi-automatic" means of forming butt joints and T-joints between sheet material. It is a further aim that such a tool be of a convenient size to be kept in any tool box and be of low cost . According to a first aspect of the invention, there is provided a joint forming tool to facilitate the formation of butt joints between sheet materials, the tool comprising:

first and second mutually perpendicular upstanding walls;

first and second resiliently biased clamping surfaces arranged respectively opposite said first and second walls and defining first and second gaps between most adjacent parts of the respective first wall/ irst clamping surface and second wall/second clamping surface; and

a base member joining bottom-most parts of said first and second walls and first and second clamping surfaces.

Preferably, both the resilient nature of the material comprising them and the shape and configuration of the first and second clamping surface combine to provide the resilient biasing.

Preferably, between a free end of each clamping surface and the respective gap region, there is defined an enlarged mouth region for accepting entry of the sheet material therein.

Preferably, said first and second resiliently biased clamping surfaces comprise material formed as a double cantilever generally as an S-shape.

Insertion of a first/second piece of sheet material into the first/second gap causes the first/second gap to widen to accommodate the sheet material therein, said first/second gap widening to the thickness of the first/second sheet material and the resiliently biased nature of the first/second clamping surface causing the first/second sheet material to be gripped between the first/second wall and the first/second clamping surface.

Preferably, a tail portion of the respective clamping surfaces is joined to the base member.

Preferably, the first and second upstanding walls meet one another to form a right angle between them.

Preferably, an upstanding edge of the second clamping surface is arranged to lie substantially in the plane defined by the first upstanding wall .

Preferably, a main extent of an edge of the first clamping surface is arranged to lie substantially within a plane defined by the second upstanding wall .

Preferably, said edge of the first clamping surface is provided with a protruding lug which protrudes beyond the plane of the second upstanding wall.

Preferably, said lug forms a lateral extension of those parts of the first clamping surface which are, in use, most adjacent to the first wall.

Preferably, in use, a first piece of sheet material to be joined to a second piece of sheet material in a butt joint is inserted in the first gap, and the second piece of sheet material is inserted into a second gap. Preferably, the first and second pieces of sheet material are, in use, slid along the base member, whilst being held within the gap until the end regions of the first and second pieces of material abut one another, in the case of a corner butt joint.

Preferably, the first piece of sheet material is slid along the base member until its leading edge is aligned along the joint between the first and second upstanding walls. Preferably, with the first sheet of material in the aforementioned position, the second sheet of material is slid along the base member until its leading edge abuts the lug of the first clamping surface .

The lug forms, in use, an automatic "end stop" at the exact thickness of the first piece of sheet material .

The tool may be composed of a single plastics member.

Alternatively, the tool may comprise multiple members, comprising an angle bracket forming the first and second upstanding walls, a top plate and a base plate forming the base member, and first and second clamping jaws forming the first and second clamping surfaces .

Preferably, the angle bracket comprises an extrusion having location means for locating the top plate and base plate to it. The location means may comprise threaded or unthreaded holes forming part of the extrusion and set screws or the like extending through apertures formed in the top and base plate to locate the top and base plates to the angle bracket . The first and second clamping surfaces may be formed from a single piece of material, which may be generally "L"- shaped in a prior to being processed state. Preferably, the free ends of the piece of material are thereafter processed by folding so as to give the first clamping surface and second clamping surface, these first and second clamping surfaces being joined to one another at their tail ends by a base part which is preferably arranged to be sandwiched, in use, between the top plate and base plate.

Alternatively, the first and second clamping surfaces may comprise separate pieces of material having a free end and a tail end, each clamping surface being held in position between the top plate and the base plate at their tail ends. Preferably, the top plate and the base plate sandwich the tail ends of the first and second clamping surfaces between them.

The first and second clamping surfaces may be provided with location holes or cut-outs to enable them to cooperate with set screws or the like which join the top plate and base plate to the angle bracket .

Alternate forms of clamping surfaces may be provided so as to accommodate a wide range of thicknesses in material .

Preferably, the first and second gaps are arranged so as to be smaller than the thinnest of material desired to be joined and, in use, as sheet materials are inserted into the respective gaps, the resiliency of the clamping surfaces enables the gaps to widen and the sheet material to be held securely between first wall/first clamping surface and second wall/second clamping surface.

According to another aspect of the invention there is provided a joint forming tool to facilitate the formation of butt joints between sheet materials, the tool comprising: first and second upstanding walls; first and second resiliently biased clamping surfaces arranged respectively opposite said first and second walls and defining first and second gaps between most adjacent parts of the respective first wall/first clamping surface and second wall/second clamping surface; and a variable angle joint mechanism permitting an angle between the first and second upstanding walls to be varied.

Preferably, the variable angle mechanism comprises a first joint member and a second joint member, the first joint member being associated with the first upstanding wall and first clamping surface and the second joint member being associated with the second upstanding wall and the second clamping surface, the first joint member and the second joint member being pivotally attached to one another.

Preferably, the pivotal axis is defined by a fastener for fastening part of the first joint member to part of the second joint member.

For a better understanding of the invention, and to show how embodiments of the same may be carried into effect, reference will now be made, by way of example, to the accompanying diagrammatic drawings in which: Figures 1 and 2 illustrate prior art methods and apparatus for butt jointing sheet materials;

Figure 3 is a perspective view of an embodiment of a joinery tool in accordance with the present invention;

Figure 4 is a sectional view along plane A, B, C, D of the tool of Figure 3 ;

Figure 5 is a plan view of the tool of Figure 3 as viewed from arrow E, but with the clamping jaws removed;

Figure 6 is a similar view to that of Figure 5, but showing the jaws in place;

Figure 7 is a bottom plan view of the joinery tool of Figures 3 to 6, showing the configuration of a base plate of the tool (hidden detail in broken lines) ;

Figure 8 shows an extrusion forming a right angle bracket of the tool of Figures 3 to 7;

Figure 9 shows lug detail of a jaw of the tool;

Figure 10 shows the tool when used for a corner butt joint;

Figure 11 shows the tool when used for a T-butt joint;

Figure 12 shows an embodiment of the invention in which the first and second clamping jaws are integral with one another forming a single piece of sheet metal; Figure 13 shows an alternate profile for a further embodiment of the tool and illustrates how separate clamping jaws may be provided and clamped in place;

Figures 14 and 15 show alternate arrangements of clamping jaws in a prior to folding state, the jaws being suitable for use with alternate angle bracket extrusion profiles;

Figure 16 shows an alternate arrangement of angle bracket; and

Figure 17 shows a further embodiment of a joint forming tool in accordance with the invention.

Referring now to Figures 3 to 10, an embodiment of a tool in accordance with the present invention will now be described. The tool comprises an angle bracket 1, a base member comprising a base plate 2 and top plate 3 of identical configurations, a first resiliently biased clamping surface formed by first clamping jaw 4, a second resiliently biased clamping surface formed by a second clamping jaw 5 and three fasteners in the form of set screws 6χ, 6₂ and 6₃.

Referring now to Figure 4, there is shown a section through the tool of Figure 3 which illustrates how the components are held together. Firstly, the clamping jaws 4, 5 comprise spring sheet steel which is folded or shaped during production so as to be reverse folded to give a double cantilever and, preferably, have an S-type formation, a tail end of the jaws being sandwiched between base plate 2 and top plate 3. The shape and configuration of the clamping jaws and the material of which they are composed combines to give them a resilient, spring, nature. This sandwich of materials is held in place by means of the set screws 6_{l t} 6₂, 6₃ which extend through apertures formed in the base and top plates 2, 3 and locate in screw holes lχ to 1₃ of the angle bracket 1. The set screws β_x to 6₃ preferably self-tap into the holes li to 1₃ of the angle bracket 1.

Referring to Figure 5, there is shown a top plan view of the tool of Figures 3 and 4, but in this view, the clamping plates , 5 have been omitted so as to show the configuration of top plate 3 (base plate 2 corresponds) in relation to the angle bracket 1. As can be seen, the base plate 3 has three distinct areas 3_X, 3₄ and 3₅, the first area 3χ is the area which supports the angle bracket 1, the second area 3₄ is the area which forms the top sandwich plate keeping in the tail end of the S-shaped jaw clamp 4 (a corresponding area 2₄ of the base plate forms the other part of the sandwich) , and the area 3_S forms the top part of a sandwich sandwiching the tail end of clamp jaw 5 (with a corresponding area 2₅ of the base plate forming the other part of that sandwich) . The sandwich of top plate 3 and base plate 2 is completed by the set screws 6χ, 6₂, 6₃ whose protruding end portions can be seen locating in screw holes li, 1₂ and 1₃ of the angle bracket 1. The upstanding external faces of the angle bracket 1 form first and second mutually perpendicular upstanding walls in the form of static clamp plates 1₄, 1 which oppose the first and second clamping jaws 4, 5 of spring steel formation.

Referring now to Figure 6, which shows the tool of Figure 3 in top plan view with clamping jaws 4, 5 in position, it can be observed that when the two clamping jaws 4, 5 are fixed in position, by the aforementioned sandwiching action, there is arranged to be formed a gap "x" and "y" between an innermost part of the folded sheet forming the jaws 4, 5 and the upstanding fixed wall 1₄, 1₅ of the angle bracket 1. These gaps "x" , "y" effectively define the minimum width of sheet material which can be joined together using this tool. It will also be observed referring to Figure 5 that one of the clamping jaws 4 is provided with a lug 4χ which protrudes from one side . The purpose of this lug 4_X will be discussed later.

Referring now to Figure 7, there is shown (from below) the construction of the base plate 2, and it will be appreciated that the construction of the top plate 3 corresponds. In Figure 7, the position of the angle bracket as it would appear on the other side of the base plate 2 and top plate 3 is shown in broken lines so as to aid comprehension of the various different areas of the base plate 2. Basically, the base plate comprises a sandwich plate having a first area 2_ι on which the angle bracket 1 (via top plate 3) is arranged to sit, in use, a second area 2 which is arranged to form the bottom sandwich layer for holding the first S-shaped clamping jaw 4 in position, and a third area 2₅ which is arranged, in cooperation with a corresponding portion 3₅ of the top plate to hold the second clamping jaw 5 in position. The first area 2_X features apertures 2_{ll f} 2_i2, 2_i3 through which the set screws β , 6₂, 6₃ may be passed. There is also shown a further optional aperture 2_X4 which may, if desired, be used (in conjunction with a similar optional hole formed in top plate 3) to fix the joinery tool to a work bench or similar by means of a screw in a semipermanent fashion.

Referring now to Figure 8, there is shown a top plan view of the angle bracket 1. In the embodiment shown, the angle bracket 1 is in fact an extrusion of material of constant cross-section. The external walls 1₄, 1_5/ providing the fixed clamping surfaces.

Considering now Figure 9, there is shown how one of the clamping jaws, in this case the first clamp jaw 4 is provided with a protruding lug 4_X which extends outwardly from an otherwise straight side edge 4₂. Side edge 4₂ is parallel to the other side edge 4₃ of first clamping jaw 4. In Figure 9, it will be appreciated that what is shown is the unfolded piece of spring steel, prior to folding to form the S-shaped first clamping jaw 4 (in other words, the raw unformed pressing is what is shown) .

Operation of the tool shown in the Figures will now be described and may best be understood by referring to Figures 3, 4, 6, 9, 10 and 11.

As mentioned previously, the first and second clamping jaws 4, 5 are made of S-shaped steel which is stainless spring steel. Referring to Figures 3, 4 and 6, with this S-shape, a piece of sheet material up to around 25mm in thickness may be inserted between the fixed wall 1₄ of the angle bracket 1 and the first clamping jaw 4, by inserting a leading edge of the sheet material into the gap "x" . Because of the shape of the jaw, there is an enlarged mouth region formed between a free end of each jaw and its respective opposing fixed surface. The mouth region is wider than the largest thickness of material which can be accepted by the clamp (formed by co-operation of jaw 4, 5 and surface 1₄, 1₅) so that the jaw 4 will automatically open (move away from fixed surface 1₄) as the material is pushed into the gap "x" so as to widen the gap ^ux" and allow full entry of the sheet.

When forming a butt joint, this first sheet of material is arranged such that its edge be brought into alignment with an edge 3_i (see Figure 5 for this edge) of top plate 3. The other sheet of material to be joined to the first sheet is then inserted, in likewise fashion, into gap "y" formed between fixed wall 1₅ and second clamp jaw 5. Again, gap "y" will expand to accommodate whatever the thickness of the sheet material to be joined is, and the material may be pushed up along the top plate 3 such that the leading edge of the material comes into contact with lug 4χ of the first clamping jaw 4. Lug 4_X is formed on the inner most part of the upper bend of the S-shape and extends outwardly beyond edge 3_i of the top plate, in line with the parts of the first clamp jaw 6 which are actually in contact with the inserted first piece of sheet material . In effect therefore this lug 4_X will always adopt a position which is defined by the outer surface (and hence the thickness) of the sheet material which has been inserted into the gap "x" . In other words, by butting up the second piece of sheet material which has been pushed into the gap "y" against the lug 4χ a perfect butt joint between the two pieces of sheet material is obtained.

The relationship described above is illustrated in Figure 10, where it can be seen that the first piece of sheet material 7 has been pushed along top plate 3 so as to have its leading edge 7χ in alignment with edge 3_4i and then the second piece of sheet material 8 has been inserted between jaws 5 and 1₅ and pushed such that its leading edge 8_X moves along top plate 3 until it comes into contact with lug 4χ. At that point, the end regions of the sheet material 7 and 8 are perfectly in alignment defining a perfect butt joint.

It will be appreciated that in Figure 10, there are shown pieces of sheet material 7, 8 which are relatively short. However, in the majority of cases these pieces of material will probably be quite significantly taller, in which case, a second tool as described may be inserted on the top edges to hold both top and bottom parts of the butt joint in alignment.

In use, because the base and top plates 2, 3 of course have some thickness, a small spacer having the same thickness as the base plates 2, may be placed under the bottom edges of the sheet materials to be joined so that a smooth sliding of the material into the tool without tilting may be achieved.

It will be appreciated that by using one such tool around a bottom area of a joint to be formed, and with another corresponding tool around the top area of the joint to be formed between two sheets of material, a very stable means of holding the sheets in butted relation is provided. The job of a user is therefore made very, very simple since all they need to do is apply the necessary glue to the edge of the board to be butted, and slide the material towards one another within the jaws of the tool. ■ With such a pair of tools top and bottom around the joint, the glue may be left to dry and, if required, the joint may also be fixed using screws etc. Indeed, screw jointing of panels can be achieved very simply whilst panels are actually in the tool, because the edge of the clamping jaws 4, 5 define perfectly the area of the butt joint formed so drilling may be carried out secure in the knowledge that the drill bit/screw will, naturally, go in the right place .

The forming of T-joints between materials may be carried out in a similar fashion to the forming of butt joints as described above and a typical T-joint is shown in Figure 11. In the case of the T-joint, the cross piece 7 is fed into the gap "x" between first clamping jaw 4 and upstanding wall 1 and positioned such that the inner edge of the T to be formed falls along edge 3₄₁. This can be done by pre-marking the sheet before feeding it into the gap "x" . The down piece 8 of the T is then fed into gap "y" and pushed until its leading edge abuts the sheet material in the gap "x" . Then, using the lug 4χ as a guide, pilot holes can be drilled through the cross piece of the T below the outstanding portion 4χ formed by the lug of the first clamping surface 4 and those screws will automatically be positioned correctly into the sheet material inserted in the gap "y" .

It will further be appreciated that because of the nature of the material and the shaping of the clamping surfaces, the use of the tool is not limited to sheet materials of the same thickness and, in fact, there can be a very large disparity between thicknesses with no problem caused whatsoever. Also, because the pieces of the clamp are held together by means of set screws holding sandwich plates joining top and base plates 3, 2 to one another, different sizes of clamping jaws can also be utilised so as to increase the range of thicknesses of materials being able to be clamped.

In the above discussion, the clamping jaws were described as being made from separate pieces of spring steel. It will of course be appreciated that alternative arrangements are possible, and may be preferred. Figure 12 shows such an arrangement in which both jaws are formed from a single piece of sheet steel. In Figure 12, the jaws are shown in a prior to folding state, with a first clamping surface 4 and a second clamping surface 5 generally defining between them an "L" -shape. For reference, there is also marked on Figure 12 the positions in which the base plate/top plate 2, 3 would normally appear (shown by broken lines ) and the locating position in which the angle bracket 1 would appear (shown by dotted lines ...) .

Referring now to Figure 13, there is shown an alternate profile of extrusion for an angle bracket 1' . There is also shown, with broken ( ) lines the outline of suitable clamping surfaces 4', 5' (prior to folding) for use with the angle bracket 1' and the position of a top plate 3', shown in dotted lines (...). It will be appreciated that the first clamping surface 4' and the second clamping surface 5' may be generally in accordance with surfaces as previously described. However, a more detailed description of such suitable clamping surfaces 4', 5' is given in relation to Figures 14 and 15 below.

Basically, the angle bracket 1' differs from the angle bracket 1, in that four location holes l'χ to 1'₄ are provided, so as to give two set screws which locate within base plate 2' and top plate 3' and with cut-outs formed in the clamping surfaces 4', 5', to give secure location of the clamping surfaces .

Referring now to Figure 14, there is shown a blank pressing of a clamping jaw 4' (again in a prior to folding state) . In this case, this pressing is suitable for individually replaceable clamping surfaces of the type discussed above in relation to Figures 13. In the embodiment illustrated, there are shown location cut-outs 4' ₅, 4' ₆ which allow the clamping surface 4' to have its tail end locate around set screws. There is also shown a cut out 4' v which cooperates with an optional hole formed in the base and top plates 2', 3' to allow the tool to be mounted on to a mounting surface, such as a work bench.

Figure 15 shows another alternative pattern of clamping surface 4'', having the same types of cut-outs for location etc., as shown in Figure 14.

Figure 16 shows a different type of angle bracket 1' ' to that described in relation to Figure 8. The angle bracket 1' ' comprises a single plastics moulding having upstanding walls 1''₄, 1^7,5 which are mutually perpendicular and having integral projections 1''₇ through 1''₉ having holes formed therethrough to enable the mounting of angle bracket 1' ' to top plate 3 and base plate 2. The angle bracket 1 ' ' further includes an end fillet portion 1 ' ' β comprising a joining member for joining the upstanding end portions of the walls 1''₄ and l''s to one another. This fillet or joining member adds strength and rigidity to the plastics moulding. It will be appreciated however that the angle bracket 1' ' functions in the same manner as the angle brackets previously described.

Referring now to Figure 17, there is shown another variation of the joint forming tool.

The bracket of Figure 17 is angle adjustable so that upstanding walls 1''' and 1'''₅ may be disposed at different angles to one another to allow joints other than right angle joints to be made. Articulation between the upstanding walls 1'''₄ and 1'''₅ is provided by means of a variable angle joint comprising a first joint part 10 and a second joint part 12 which are pivotally attached to one another about a pivotal axis F, defined by a fastener comprising bolt 14 and nuts 15, 16, the bolt 14 passing through appropriately shaped overlapping apertures formed in the first and second joint parts 10, 12.

Aside from the aforementioned features, the joint forming tool of Figure 17 functions in similar fashion to the previously described tools, but is particularly useful for holding pieces of metal together during welding operations, where angles other than 90 degree angle welds are required.

To sum up, by using the tool of the present invention, the edges of one sheet of material can be arranged to automatically line up with the edges of the other sheet at exactly 90°. Glue could be applied just before joining the two components together safe in the knowledge that the two parts are not going to slide about during fixing of the joint. Also, drilling and countersinking of screw holes can be made in exactly the right place with confidence. To glue without screws, the tool holds the glued sheets in perfect alignment leaving both hands free to locate and tighten any other long clamps which might be desired without any sliding of the glued pieces.

Further, alignment of T-joints is made simple by the unique design of the clamping jaws. Simply measure and mark correctly where you want the joint on both top and bottom of the work piece, line up the edge of the jaw to the measurement and line up and locate the boards in position.

The tool automatically adjusts to thickness of the board, because the jaws automatically adjust independently.

It will further be appreciated that although in this application we have specifically referred to spring steel etc, it is equally possible for the clamp to be made out of plastics material, using the same principles. Many tough high resiliency plastics are available these days and the tool of the present application would lend itself to such implementation.

The reader's attention is directed to all papers and documents which are filed concurrently with or previous to this specification in connection with this application and which are open to public inspection with this specification, and the contents of all such papers and documents are incorporated herein by reference.

All of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive.

Each feature disclosed in this specification (including any accompanying claims, abstract and drawings), may be replaced by alternative features serving the same, equivalent or similar purpose, unless expressly stated otherwise. Thus, unless expressly stated otherwise, each feature disclosed is one example only of a generic series of equivalent or similar features.

The invention is not restricted to the details of the foregoing embodiment (s) . The invention extend to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings) , or to any novel one, or any novel combination, of the steps of any method or process so disclosed.

Claims

1. A joint forming tool to facilitate the formation of butt joints between sheet materials, the tool comprising:

first and second mutually perpendicular upstanding walls;

first and second resiliently biased clamping surfaces arranged respectively opposite said first and second walls and defining first and second gaps between most adjacent parts of the respective first wall/first clamping surface and second wall/second clamping surface; and

2. A tool according to claim 1, wherein both the resilient nature of the material comprising them and the shape and configuration of the first and second clamping surface combine to provide the resilient biasing.

3. A tool according to claim 1, wherein between a free end of each clamping surface and the respective gap region, there is defined an enlarged mouth region for accepting entry of the sheet material therein.

4. A tool according to claim 1, wherein said first and second resiliently biased clamping surfaces comprise material formed as a double cantilever generally as an S- shape.

5. A tool according to claim 1, wherein insertion of a first/second piece of sheet material into the first/second gap causes the first/second gap to widen to accommodate the sheet material therein, said first/second gap widening to the thickness of the first/second sheet material and the resiliently biased nature of the first/second clamping surface causing the first/second sheet material to be gripped between the first/second wall and the first/second clamping surface.

6. A tool according to claim 1, wherein a tail portion of the respective clamping surfaces is joined to the base member.

7. A tool according to claim 1, wherein the first and second upstanding walls meet one another to form a right angle between them.

8. A tool according to claim 1, wherein an upstanding edge of the second clamping surface is arranged to lie substantially in the plane defined by the first upstanding wall.

9. A tool according to claim 1, wherein a main extent of an edge of the first clamping surface is arranged to lie substantially within a plane defined by the second upstanding wall.

10. A tool according to claim 9, wherein said edge of the first clamping surface is provided with a protruding lug which protrudes beyond the plane of the second upstanding wall.

11. A tool according to claim 10, wherein said lug forms a lateral extension of those parts of the first clamping surface which are, in use, most adjacent to the first wall .

12. A tool according to claim 1, wherein, in use, a first piece of sheet material to be joined to a second piece of sheet material in a butt joint is inserted in the first gap, and the second piece of sheet material is inserted into a second gap .

13. A tool according to claim 12, wherein the first and second pieces of sheet material are, in use, slid along the base member, whilst being held within the gap until the end regions of the first and second pieces of material abut one another, in the case of a corner butt joint.

14. A tool according to claim 13, wherein the first piece of sheet material is slid along the base member until its leading edge is aligned along the joint between the first and second upstanding walls.

15. A tool according to claim 1, wherein the first and second clamping surfaces are formed from a single piece of material, which may be generally "L" -shaped in a prior to being processed state, the free ends of the piece of material being thereafter processed by folding so as to give the first clamping surface and second clamping surface, these first and second clamping surfaces being joined to one another at their tail ends by a base part which is preferably arranged to be sandwiched, in use, between a top plate and a base plate.

16. A tool according to claim 1, wherein the first and second clamping surfaces may comprise separate pieces of material having a free end and a tail end, each clamping surface being held in position between a top plate and a base plate at their tail ends.

17. A tool according to claim 16, wherein the top plate and the base plate sandwich the tail ends of the first and second clamping surfaces between them.

18. A tool according to claim 1, wherein the first and second gaps are arranged so as to be smaller than the thinnest of material desired to be joined and, in use, as sheet materials are inserted into the respective gaps, the resiliency of the clamping surfaces enables the gaps to widen and the sheet material to be held securely between first wall/first clamping surface and second wall/second clamping surface .

19. A joint forming tool to facilitate the formation of butt joints between sheet materials, the tool comprising:

first and second upstanding walls;

a variable angle joint mechanism permitting an angle between the first and second upstanding walls to be varied.

20. A joint forming tool according to claim 19, wherein the variable angle mechanism comprises a first joint member and a second joint member, the first joint member being associated with the first upstanding wall and first clamping surface and the second joint member being associated with the second upstanding wall and the second clamping surface, the first joint member and the second joint member being pivotally attached to one another.

21. A joint forming tool according to claim 19, wherein the pivotal axis is defined by a fastener for fastening part of the first joint member to part of the second joint member.

22. A tool according to claim 19, wherein both the resilient nature of the material comprising them and the shape and configuration of the first and second clamping surface combine to provide the resilient biasing.

23. A tool according to claim 19, wherein between a free end of each clamping surface and the respective gap region, there is defined an enlarged mouth region for accepting entry of the sheet material therein.

24. A tool according to claim 19, wherein said first and second resiliently biased clamping surfaces comprise material formed as a double cantilever generally as an S- shape .

25. A tool according to claim 19, wherein insertion of a first/second piece of sheet material into the first/second gap causes the first/second gap to widen to accommodate the sheet material therein, said first/second gap widening to the thickness of the first/second sheet material and the resiliently biased nature of the first/second clamping surface causing the first/second sheet material to be gripped between the first/second wall and the first/second clamping surface.

26. A tool according to claim 19, wherein, in use, a first piece of sheet material to be joined to a second piece of sheet material in a butt joint is inserted in the first gap, and the second piece of sheet material is inserted into a second gap .

27. A tool according to claim 19, wherein the first and second gaps are arranged so as to be smaller than the thinnest of material desired to be joined and, in use, as sheet materials are inserted into the respective gaps, the resiliency of the clamping surfaces enables the gaps to widen and the sheet material to be held securely between first wall/first clamping surface and second wall/second clamping surface.