AU2013227997B2 - Method and Device for Cutting Angled Joints - Google Patents

Abstract

A jig for cutting joint pieces such as mitre joint pieces for framing. The jig has a supporting member with an upper surface upon which the joint piece may be laid. A fence extends above the upper surface of the supporting member, so that a lateral edge of the joint piece may abut the fence in order to align the joint piece relative to a cutting angle. A lateral edge of the supporting surface is a guide surface and is configured to travel against a cutting blade guide so that the cutting blade may be passed across the joint piece to cut the joint piece at the cutting angle. The guide surface is at an angle to the fence which defines the cutting angle. Figure 2 Figure 3 ------ --- ---- !-- 7

Description

Cross-Reference To Related Applications [0001] This application claims the benefit of Australian Provisional Patent Application No. 2012904014 filed 14 September 2012, which is incorporated herein by reference.

Technical Field [0002] The present invention relates to a method and device for cutting angled joints, including mitre joints, for example for construction of frames including wooden picture frames

Background of the Invention [0003] To form a mitre joint, two joint pieces are brought together. To ensure that the two joint pieces fit closely together and conform to each other to form the joint, accurate cutting or forming of the joint pieces is required. Typically, joint pieces are cut into shape by use of a drop saw, guillotine or hand saw, however these approaches can only provide planar abutting faces of the joint pieces and creation of simple butt joints, and do not allow creation of more complex joint faces such as tongue and groove joints or other interlocking joint profiles.

[0004] To secure two joint pieces together to form a mitre joint, such planar abutting faces are generally glued together, however with planar surfaces glue alone usually provides insufficient strength to the joint and additional fasteners such as V-nails are typically added. Such fasteners are typically applied to the rear of the frame however they are nevertheless unsightly and add a production step and add cost. Moreover, in the case of a timber frame the planar abutting faces of each joint piece invariably present the end-grain of the timber, bringing the disadvantages of end-grain to end-grain gluing which can be particularly weak.

[0005] Drop saws and guillotines generally must have a cutting edge which is longer than the largest cross-sectional dimension of the joint piece being cut. To cater for joint angles other than 90 degrees (i.e. joint cuts at 45 degrees), drop saws often provide a hinged tilting mechanism to change the relative angle between the joint piece and the cutting blade, allowing cut angle selection. However hinge mechanisms tend to have some amount of play, or imprecision, giving rise to small but significant cut angle errors. Infinitely variable angle selection also permits absolute angle positioning errors. Consequently when setting the cut angle these tools generally require the user to make trial cuts, repeated adjustments, and/or calibrations. Consequently drop saws tend to be relatively large, expensive and complex, which deters their use for small jobs or by infrequent users such as hobbyists. Even small remaining cut angle errors will be magnified, as a four-sided mitred frame requires eight cuts and repeating the same cut angle error in each cut is cumulative. Thus any cut angle error will result in wedge-shaped gaps showing when the frame is assembled, with the problem being exacerbated for frame pieces of greater width.

[0006] Any discussion of documents, acts, materials, devices, articles or the like which has been included in the present specification is solely for the purpose of providing a context for the present invention. It is not to be taken as an admission that any or all of these matters form part of the prior art base or were common general knowledge in the field relevant to the present invention as it existed before the priority date of each claim of this application.

[0007] Throughout this specification the word "comprise", or variations such as "comprises" or "comprising", will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Summary of the Invention [0008] According to a first aspect the present invention provides a jig for cutting joint pieces, the jig comprising: a supporting member which in use presents an upper surface upon which the joint piece may be laid; a fence which in use extend s above the upper surface of the supporting member and against which a lateral edge of the joint piece may abut in order to align the joint piece relative to a fixed cutting angle; and a lateral edge of the supporting surface being a guide surface, configured to travel against a cutting blade guide of a cutting blade which rotates in a plane substantially parallel to the upper surface of the supporting member, so that the cutting blade may be passed across the joint piece to cut the joint piece at the fixed cutting angle, the guide surface being at an angle to the fence which defines the fixed cutting angle; wherein the jig is a hand tool configured to be moved by hand, and wherein the jig is configured to move freely across a work table bearing the cutting blade.

[0009] According to a second aspect the present invention provides a method of cutting joint pieces, the method comprising: positioning a joint piece upon an upper surface of a supporting member of a jig, and against a fence of the jig, and cantilevered over a lateral edge of the supporting surface which defines a guide surface; and moving the jig by hand freely across a work table bearing a cutting blade which rotates in a plane substantially parallel to the upper surface of the supporting member, so as to bring the jig together with the cutting blade, and so as to pass a cutting blade guide along the guide surface of the jig and thereby passing the cutting blade across the joint piece to cut the joint piece at a fixed cutting angle, the fixed cutting angle being defined by the jig as being the fixed angle between the guide surface and the fence.

[0010] According to a third aspect the present invention provides a joint cutting system comprising: a cutting blade and cutting blade guide, mounted at a fixed location on a work table, the cutting blade rotating in a plane substantially parallel to a surface of the table; and a jig in accordance with the first aspect of the invention, configured to be moved across the surface of the table, to effect cutting of a joint piece mounted on the jig.

[0011] Some embodiments of the present invention may be particularly suitable for simple formation of frame pieces which may be brought together to form mitre joints, for example for window frames, picture frames or boxes.

[0012] By providing a jig which presents joint pieces at a fixed angle, the present invention avoids angle inaccuracies which typically arise if a hinged jig is used to define a joint piece face angle, and offers a very simple solution for small jobs and/or infrequent users. The fixed angle may be 45 degrees for formation of 90 degree mitre joints for rectangular items, or any other suitable angle such as 30 degrees for formation of 60 degree joints for hexagonal items, 22.5 degrees for formation of 45 degree joints for octagonal items or any other suitable angle. A set of jigs in accordance with the present invention, each providing a unique cut angle, may be provided.

[0013] In preferred embodiments a clamp is provided in order to clamp the joint piece to the jig. The clamp may be configured to clamp the joint piece to the fence or to the supporting member.

[0014] Preferred embodiments provide a releasably fixable stop against which uncut joint pieces may be abutted, in order to ensure a plurality of joint pieces may be cut to the same length by reference to the stop. The stop may be slidably mounted on the fence and slidable along the fence and releasably fixable upon the fence for this purpose.

[0015] In embodiments having a stop one or more stop positioners may be provided. Each stop positioner is preferably configured to position the stop when the stop is brought against the positioner, so that a stop position may be defined by the stop positioner. When using two stop positioners and cutting joint pieces for a rectangular frame, for example, such embodiments permit the stop to be repeatedly and reliably brought to a first stop position which defines a first frame piece length, and repeatedly and reliably brought to a second stop position which defines a second frame piece length. The or each stop positioner is preferably slidably mounted upon the fence and releasably fixable at any desired location along the fence, for example by clamping.

[0016] The present invention is further advantageous in that the joint piece will, in typical usage, be laid flat upon the upper surface of the supporting member, so that the largest cross-sectional dimension of the joint piece extends alongside the guide surface, and so that the cutting blade need merely span the smallest cross sectional dimension of the joint piece. This reduces the required size of the cutting edge used to cut the joint piece.

[0017] The supporting member is preferably a continuous base plate presenting a continuous planar upper surface upon which the joint piece may be placed. Alternatively the supporting member may be porous, have apertures or cavities, and/or may consist of a plurality of supporting sub-members which collectively function to support the joint piece.

[0018] In preferred embodiments, the supporting member is marked with scale lines or other scale indicia, to assist positioning of the joint piece in a manner which will result in a desired internal or external dimension of the piece after cutting. Such embodiments are particularly advantageous in picture framing where it is desired that the internal dimension of the frame should precisely match, or be precisely proportional to, the dimensions of the picture being framed. The scale lines are preferably parallel to the guide surface, but provided at gradations as measured along the fence. Providing the scale lines parallel to the guide surface provides a measure of the internal or external dimension of the joint piece irrespective of the width of the piece as measured laterally from the fence.

[0019] The fence is preferably a continuous fence, or alternatively may be comprised of a plurality of elements which together function to align the joint piece when it abuts the plurality of elements.

[0020] The cutting blade may comprise a table-mounted router, a spindle moulder or other table-mounted rotating cutter. The cutting blade preferably rotates in a plane substantially parallel to the upper surface of the supporting member. The cutting blade can have a constant radius at all points along the axis of rotation such that the cut face of the joint piece is planar, or may have a non-constant radius such that the cut face of the joint piece is non-planar. For example the cutting blade may have a stepped radius configured to form splines along the cut face of the joint piece.

[0021] The cutting blade may in some embodiments be configured to form an anti-symmetric profile along the face of the joint piece, such that two joint pieces cut by the same blade when brought together form a flush interlocking fit. However in alternative embodiments of the invention the profile along the face of the joint piece need not be anti-symmetric if two complementary cutting blades are used to cut abutting joint pieces. Formation of interlocking joint pieces, whether by use of a single anti-symmetric blade or by two complementary blades, is advantageous in providing an interlocking joint of improved strength.

[0022] The cutting blade guide against which the guide surface of the jig is pressed during cutting may comprise a bearing of the rotating cutting blade, a template follower, or other suitable cutting blade guide.

[0023] The method of cutting preferably includes making multiple passes of the cutting blade guide along the jig guide surface, to ensure that the cut is made along the proper profile as defined by the guide surface along the full width of the joint piece.

[0024] In some embodiments of the invention, a lateral dimension of the support member, as measured laterally from the fence to a second lateral edge of the support member, may be equal to a desired joint piece width. In such embodiments, the second lateral edge of the support member is preferably configured to act as a guide surface to travel against the cutting blade guide so that the cutting blade may be passed along the joint piece to thickness the joint piece to the desired joint piece width. In other embodiments, the lateral dimension of the support member, as measured laterally from the fence to a second lateral edge of the support member, is larger than an intended joint piece width, and appropriately dimensioned spacing pieces are provided to space the joint piece by a desired distance away from the fence, to obtain the desired joint piece width when the cutting blade is passed along the second lateral edge to thickness the joint piece. Such embodiments may be advantageous in avoiding the need for a separate thicknessing tool. However in alternative embodiments the lateral dimension of the support member, as measured laterally from the fence to a second lateral edge of the support member, is larger or smaller than an intended joint piece width so that in such embodiments the jig is not configured for joint piece thicknessing.

Brief Description of the Drawings [0025] An example of the invention will now be described with reference to the accompanying drawings, in which:

Figure 1 is a perspective view of a mitre jig in accordance with one embodiment of the present invention;

Figure 2 is a plan view of the mitre jig of the embodiment of Figure 1;

Figure 3 is a side elevation view of the mitre jig of the embodiment of Figure 1;

Figure 4 is an end elevation view of the mitre jig of the embodiment of Figure 1;

Figure 5 is an end perspective view of the mitre jig of the embodiment of Figure 1;

Figure 6 is a partial cross-sectional view illustrating use of the jig to cause a straight cutting blade to cut a work piece; and

Figure 7 is a partial cross-sectional view illustrating use of the jig to cause an antisymmetric cutting blade to cut a work piece.

Description of the Preferred Embodiments [0026] Figure 1 is a perspective view of a mitre jig 100 in accordance with one embodiment of the present invention. The mitre jig 100 is a device to assist in cutting angled joints at 45° as used in rectangular frame construction. The device consists of a supporting member in the form of a base plate 101. The base plate 101 presents an upper surface upon which joint piece to be cut may be laid. The jig 100 is configured for cutting at a single angle, in this case 45 degrees. The cutting angle 0c is defined by an angled guide surface 102 machined across one end of the base plate 101. The guide surface 102 is provided at a lateral edge of the supporting surface of the base plate 101, and the guide surface 102 is configured to travel against a cutting blade guide so that the cutting blade may be passed across the joint piece to cut the joint piece at the cutting angle. The angle between guide surface 102 and fence 103, as viewed from above and as shown in Figure 2, is 45 degrees in this embodiment, and defines the cutting angle 0c. The fence 103 rises above the upper surface of the base plate 101, so that a lateral edge of the joint piece may abut against the fence, in order to align the joint piece relative to the guide surface to ensure the cutting angle is effected.

[0027] The fence 103 is a longitudinal member mounted firmly within a slot machined into the supporting member 101. The mitre jig 100 may be provided with a fence 103 of a metre or more in length for large jobs, or the fence 103 may be of the order of 10-40cm for domestic framing -type jobs, or any other suitable length.

[0028] A rule, consisting of a plurality of scale lines parallel to the guide surface 102 and a portion of which is indicated generally by 112, is inscribed on the base plate 101. Notably, the scale lines are parallel to guide surface 102 but are calibrated to distance as measured along the fence 103. For example, in this embodiment the scale lines are at 1cm spacing as measured along the fence, but being at a 45 degree angle, the scale line spacing measured at a normal to the scale lines is less than 1cm, specifically 1/V2 cm. This configuration ensures that the dimension of a cut piece may be simply measured from the guide surface irrespective of the width of the joint piece as measured perpendicular to the fence. Numerical indications of distance may also be provided on or adjacent the scale lines.

[0029] Fence 103 is a Tee Track sectional extrusion, and is fixed along the middle of the base plate 101 such that the angle between 102 and 103 is the required cutting angle, as discussed above. The fence 103 is fitted with two sliding stop blocks 104 and 105, also referred to as stop positioners, and between the stop blocks 104 and 105 the fence 103 is equipped with a sliding fence 106, also referred to as a stop. Each stop positioner 104, 105 is configured to position the stop 106 when the stop 106 is brought against the respective positioner, so that a respective stop position may be defined by each stop positioner 104 and 105. When using two stop positioners and when cutting joint pieces for a non-square rectangular frame, for example, such embodiments permit the stop 106 to be repeatedly and reliably brought to a first stop position defined by stop positioner 104 which defines a first frame piece length, and repeatedly and reliably brought to a second stop position defined by stop positioner 105 which defines a second frame piece length. Each stop positioner 104, 105 is slidably mounted upon the fence 103 and is releasably fixable at any desired location within a respective range of freedom along the fence 103, by turning the associated screw clamp. The sliding fence 106 may be at an angle or perpendicular to the fence 103, such that the frame piece can be brought up against an angled or perpendicular surface to form the stop. In this embodiment of the invention, and as indicated in Figure 2, the sliding fence 106 has a first face 1064 which is presented at 45 degrees to the fence 103, and a second face 1062 which is presented at 90 degrees to the fence 103. The sliding fence 106 can be repositioned such that either the straight edge 1062 or the angled edge 1064 is presented to a joint piece extending towards the guide surface 102, so as to set the frame piece length. Selection of which face 1062 or 1064 is presented to a joint piece is achieved by removing the sliding fence 106 from the fence 103, rotating the sliding fence 106 by 180 degrees, and repositioning the sliding fence 106 in the Tee Track 103.

[0030] A clamp 107 is provided and can be used to hold the work piece down against the base plate 101. In alternative embodiments the clamp may be configured to clamp the work piece against the fence 103. Any suitable number of clamps can be used in conjunction.

[0031] A handle 109 is fitted to the base plate 101 for improved user control of the jig 100 during cutting, and for safety. The handle 109 may in alternative embodiments be adjustably mounted to the jig to permit handle position selection for ergonomic or other reasons. In this embodiment, the user is likely to use their right hand on handle 109 and place their left hand upon the fence 103 distal from the cutting blade. Alternative embodiments, which may be preferable for left-handed users, may provide a jig which is the mirror image of jig 100 as reflected about a nominal line along or proximal to the fence, so that the handle is instead naturally presented to the user’s left hand. In such left-handed embodiments, the rotational direction of the cutter and the cutting blade design are preferably chosen or configured so that a suitable cut is made when the work piece is passed along the cutter by a left-handed user.

[0032] As shown in Figure 6, in use the device 100 is moved by hand, with the base plate 101 moving freely across a work table 600, and is brought against a rotating cutter 610 which has a bearing 612 fitted to its shank 614, such that the bearing 612 follows the machined guide surface 102. The constraint on the relative movement between the jig 100 and the cutting blade 610 which is afforded by the guide surface 102 is what defines the 45 degree cutting angle which will be created in the work piece 620, from passing the cutting blade bearing 612 along the surface 102. The profile of the cutting blade 610 is what defines the profile of the joint face 622 of the work piece 620. In this embodiment the profile of the joint face 622 of the work piece created by cutting blade 610 is planar, so that when the same blade is used to cut another work piece, the respective joint faces of the two work pieces may be brought together to form a butt joint.

[0033] As shown in Figure 7 an alternative profile of cutting blade 710 defines an alternative profile of the joint face 722 created in the work piece 720. In this embodiment the profile of the joint face 722 of the work piece created by cutting blade 710 is anti-symmetric, so that when the same blade 710 is used to cut another work piece, the respective joint faces of the two work pieces may be brought together to form an interlocked mitre joint. When this interlocking joint is glued it will have considerably greater strength than a planar glued mitre joint, reducing or eliminating the need for additional mechanical strengthening such as v-nails. In the embodiment of Figure 7 and other embodiments in which an anti-symmetric cutting blade is used, some adjustment in cutter height may be required to allow for the joint piece thickness, to ensure antisymmetry and a flush fitting joint. As will be appreciated, by appropriate selection of the profile of cutting blade 710, the jig 100 permits a wide range of interlocking mitre joint profiles to be cut simply and at an accurate cut angle. Interlocked joint face profiles provide automatic alignment of the joint as they settle together, as well as providing much greater strength in the joint once it is assembled and glued, reducing or obviating the need for mechanical strengthening of the glued joint. As shown in Figures 6 and 7, the cutter 610, 710 extends slightly below the upper surface of the supporting member 101, to ensure that the cutting blade trims the entire workpiece 620, 720.

[0034] The present embodiment thus provides a simple and accurate method of cutting plain joints and interlocking joints at an angle, typically 45°, as used in frame construction. With this device the angle of the joint is pre-determined in the manufacture of the jig 100, thus eliminating any potential for errors arising from adjustments of hinged cutting tools, simplifying and thereby reducing the cost of construction of the device, and simplifying use of the device.

[0035] The jig 100 may thus be used in conjunction with a table-mounted router. A router bit, typically a straight bit 610 with a bearing or a tongue and groove bit 710 with a bearing, is fitted to the router. In use the bearing 612 will run against the angled surface 102 with the cutter 610 following along at the same angle above this surface. The workpiece 620 is clamped to the device 100 with one or more clamps 107, such that the workpiece 620 is against the fence 103 and slightly overhanging the end of the supporting surface 101. The sliding fence 106 is held against the far end of the workpiece 620. When a user wishes to cut multiple joint pieces, each to one of two different lengths, the sliding stop blocks 104 and 105 are positioned to locate the sliding fence 106 in the respective desired position. The jig 100 is then moved across the router table and onto the cutter by hand, so that the bearing 612 runs against and along the guide surface 102 with the cutting direction along this guide surface 102 being towards the fence 103.

[0036] Prior to use of jig 100, the bulk of waste material of the workpiece may be removed by some other method (bandsaw, drop saw, hand saw etc.), so that a single pass, or a small number of passes, with the device 100 against the cutter 610 produces the finished half of one joint. Alternatively the waste could be removed using the jig 100 by making as many passes as required.

[0037] After one end of the workpiece 620 has been cut, the workpiece is turned over to swap ends, keeping the same long edge of the workpiece against the fence 103. The procedure described previously is then repeated to cut the second end of the workpiece 620. This procedure can then be repeated to produce all the other pieces of the frame, box or item being made.

[0038] Notably, when the workpiece is timber, the mode of operation of the present embodiment provides for the cutting blade to make a “climbing cut” across the grain, giving an extremely clean finish as compared to cross cuts made by drop saws or the like.

[0039] It will be appreciated by persons skilled in the art that numerous variations and/or modifications may be made to the invention as shown in the specific embodiments without departing from the spirit or scope of the invention as broadly described. For example, in alternative embodiments there may additionally or alternatively be provided: additional stop blocks; a cutting angle of 30 degrees, 22.5 degrees, or other desired angle; and/or a thicknessing guide surface on the edge of the base plate 101 parallel to the fence. The present embodiments are, therefore, to be considered in all respects as illustrative and not restrictive.

Claims (19)

1. CLAIMS:

   1. A jig for cutting joint pieces, the jig comprising: a supporting member which in use presents an upper surface upon which the joint piece may be laid; a fence which in use extends above the upper surface of the supporting member and against which a lateral edge of the joint piece may abut in order to align the joint piece relative to a fixed cutting angle; and a lateral edge of the supporting surface being a guide surface, configured to travel against a cutting blade guide of a cutting blade which rotates in a plane substantially parallel to the upper surface of the supporting member, so that the cutting blade may be passed across the joint piece to cut the joint piece at the fixed cutting angle, the guide surface being at an angle to the fence which defines the fixed cutting angle; wherein the jig is a hand tool configured to be moved by hand, and wherein the jig is configured to move freely across a work table bearing the cutting blade.
2. 2. The jig of claim 1, wherein the fixed cutting angle is 45 degrees, for formation of 90 degree mitre joints.
3. 3. The jig of claim 1 or claim 2 further comprising a clamp configured to clamp a joint piece to the jig.
4. 4. The jig of any one of claims 1 to 3 further comprising a releasably fixable stop mounted on the fence and slidable along the fence, against which uncut joint pieces may be abutted in order to ensure a plurality of joint pieces may be cut to the same length by reference to the stop.
5. 5. The jig of claim 4 further comprising at least one stop positioner configured to position the stop when the stop is brought against the positioner, a stop position being defined by the stop positioner.
6. 6. The jig of claim 5 wherein the or each stop positioner is slidably mounted upon the fence and releasably fixable at desired locations along the fence.
7. 7. The jig of any one of claims 1 to 6 further comprising scale indicia marked upon the supporting member to assist positioning of the joint piece in a manner which will result in a desired internal or external dimension of the piece after cutting.
8. 8. The jig of claim 7 wherein the scale indicia are scale lines marked parallel to the guide surface, provided at gradations as measured along the fence.
9. 9. The jig of any one of claims 1 to 8, wherein a lateral dimension of the support member as measured laterally from the fence to a second lateral edge of the support member is equal to a desired joint piece width, and wherein the second lateral edge of the support member is configured to act as a guide surface to travel against the cutting blade guide so that the cutting blade may be passed along the joint piece to thickness the joint piece to the desired joint piece width.
10. 10. A method of cutting joint pieces, the method comprising: positioning a joint piece upon an upper surface of a supporting member of a jig, and against a fence of the jig, and cantilevered over a lateral edge of the supporting surface which defines a guide surface; and moving the jig by hand freely across a work table bearing a cutting blade which rotates in a plane substantially parallel to the upper surface of the supporting member, so as to bring the jig together with the cutting blade, and so as to pass a cutting blade guide along the guide surface of the jig and thereby passing the cutting blade across the joint piece to cut the joint piece at a fixed cutting angle, the fixed cutting angle being defined by the jig as being the fixed angle between the guide surface and the fence.
11. 11. The method of claim 10, further comprising making multiple passes of the cutting blade guide along the jig guide surface, to ensure that the cut is made along the proper profile as defined by the guide surface along the full width of the joint piece.
12. 12. A joint cutting system comprising: a cutting blade and cutting blade guide, mounted at a fixed location on a work table, the cutting blade rotating in a plane substantially parallel to a surface of the table; and a jig in accordance with any one of claims 1 to 9, configured to be moved across the surface of the table, to effect cutting of a joint piece mounted on the jig.
13. 13. The joint cutting system of claim 12, wherein the cutting blade comprises a table-mounted router.
14. 14. The joint cutting system of any one of claims 12 to 13, wherein the cutting blade has a constant radius at all points along the axis of rotation such that the cut face of the joint piece is planar.
15. 15. The joint cutting system of any one of claims 12 to 13, wherein the cutting blade has a nonconstant radius along the axis of rotation such that the cut face of the joint piece is non-planar.
16. 16. The joint cutting system of claim 15 wherein the cutting blade has a stepped radius configured to form tongues and grooves along the cut face of the joint piece.
17. 17. The joint cutting system of claim 16 wherein the cutting blade is configured to form an anti-symmetric profile along the face of the joint piece, such that two joint pieces cut by the same blade when brought together form a flush interlocking fit.
18. 18. The joint cutting system of any one of claims 12 to 17 wherein the cutting blade guide against which the guide surface of the jig is pressed during cutting comprises a bearing of the rotating cutting blade.
19. 19. A set of jigs each in accordance with any one of claims 1 to 9, each jig providing a unique respective fixed cutting angle.