AU761662B2 - Router guidance system for the production of mortise-and-tenon joints - Google Patents

Description

WO 00/56508 PCTIAUOO/00192 1 ROUTER GUIDANCE SYSTEM FOR THE PRODUCTION OF MORTISE-AND-TENON

JOINTS

FIELD OF THE INVENTION The present invention relates to the field of woodworking and in particular to a system for producing mortise-and-tenon joints.

BACKGROUND

The mortise-and-tenon joint has been used in woodworking fields since antiquity. Briefly, and with reference to Figure 1A and 1B, the joint is identified by a mortise aperture, form-ed into one piece of timber while on another a tongue shaped tenon is formed for insertion into the aperture. With reference to Figure 1C it will be noted that the face 14 of tenon 8 is formed so that tenon 8 fits snugly into mortise 16. That is, the tenon and the mortise are formed to complement each other. It is also highly preferable, though not essential that the length 18 of tenon 8 is the same as the depth 20 of mortise 2.

Because the mortise-and-tenon is used in diverse applications, numerous methods exist for its formation. Probably the simplest method of making the joint is to form the mortise aperture by means of a chisel and the tenon with a small handsaw. There are at least two problems associated with this method. Firstly considerable experience is required in order that the mortise and tenon are formed with a good fit. All too often "sloppy" joints are formed which rely on the use of fillers and glue rather than primarily on the mechanical interaction of the tenon in the mortise. Joints in which the tenon ill-fits the mortise are susceptible to glue failure and associated weaknesses.

Altemrnatively, if it is the case that the tenon is over-dimensioned then further work such as sanding or shaving will be required in order to make the tenon fit its intended mortise.

A second problem is that hand tools are not well suited to forming mortise-and-tenon joints in particularly hard timbers.

More recently powered plunger routers have been found to be useful when making a mortise. The plunger router is placed on the workpiece with the bit set to a position above the router base.

WO 00/56508 PCT/AU00/00192 2 The bit is then lowered into the work until it reaches a preset stop which defines the depth of the mortise. A fence is arranged to guide the router base along a straight path in order that the router cutter forms a straight mortise slot.

Power tool methods are also known for forming tenons. For example it is well known to use a table saw to cut tenons. Another method is described in the article "An Adjustable Tenoning Jig" by Neil Scobie in Australian Woodworker November/December 1998. at p30. According to that method a power router is used to cut tenons. The base of the router is guided against a fence to cut the sides of the tenons. It is explained in the article that "It will take a bit of fiddling around to get the tenons [to form] a firm, but riui ioo tight, fit in the mortise. You may need to take off a couple of shavings if the fit is too tight, or add a strip of masking tape if the fit is too loose." Clearly none of the above approaches to the formation of complementary mortises and tenons is satisfactory. On the one hand the use of chisels and saws requires considerable experience before snug-fitting joints are produced.

Alternatively while the use of power tools reduces the labour required to fashion the joints it remains the case that considerable trial and error may be required before snug-fitting mortises and tenons are achieved.

In light of the prior art it is an object of the present invention to provide a an apparatus for forming complementary tenons and mortises to a high degree of accuracy thereby facilitating the formation of well-fitting mortise-and-tenon joints.

SUMMARY OF THE INVENTION According to the present invention there is provided a router guiding system for the formation of mortise-and-tenon joints by means of a router, said router including a cutting bit and a guide for said bit, said router guiding system including: a) a first guiding means shaped so that upon moving said router in concert with said guiding means a mortise is described by said cutting bit; and b) a-second guiding means shaped so that upon moving said guide in concert with said second guiding means a tenon is described by said cutting bit; wherein said first and second guiding means are formed so that said tenon WO 00/56508 PCT/AU00/00192 3 and said mortise are of complementary shapes.

Preferably said first and second guiding means comprise respective first and second slots formed into a plate wherein operatively said guide is moved around and in contact with the peripheries of said first and second slots.

Alternatively said first and second guiding means may comprise respective first and second slots formed into respective first and second plates, wherein operatively said guide is moved around and in contact with the peripheries of said first and second slots.

Preferably, given that said guide is of a radius R1 and said cutter is of a !0 radius R2, said first slot is rectangularly shaped for the formation of riurtise apertures of width D and length Z, said first slot having width W and length L, where W=D+2 x (R1-R2) and L =Z+2 x (R1-R2) and said second slot is rectangularly shaped with filleted corners for the formation of tenons of width D and length Z, said second -slot having width Th and length Y where Th=2 x (R2+R1)+D and Y=Z+2 x (R2+R1) said second slot being filleted with a fillet radius of 2R2 R1.

Preferably the plate(s) include means for mounting to a stand.

According to a further aspect of the present invention there is provided a stand for mounting a plate of a template system as previously described, said stand including means for engaging said template means for mounting a workpiece adjacent said template and means for rotating said template and said workpiece.

Preferably such a stand will have a means for mounting said workpiece arranged to facilitate variations in angular orientation between said workpiece and said template.

Preferably said router guiding system further includes a means for ensuring that the depth of said mortise and the length of said tenon are the same.

BRIEF DESCRIPTION OF THE DRAWINGS Figure l.A depicts a prior art exploded perspective view of a mortise-andtenon joint.

WO 00/56508 PCT/AU00/00192 4 Figure 1B is an exploded plan cross-sectional view of the mortise-andtenon joint of Figure 1.

Figure 1C depicts tenon 6 of Figure 1 viewed in the direction B-B and mortise 2 viewed in the direction A-A.

Figure 1D depicts a mortise-and-tenon cutting template according to the present invention.

Figure 2 depicts the underside of a router.

Figure 3 depicts the dimensions of the cutting bit and guide of a router.

Figure 4 depicts the dimensions of the mortise slot of the template of Figure 1.

Figure 5 depicts the dimensions of the tenon slot of the template of Figure 1.

Figure 6 depicts a stand for use with the template of Figure 1.

Figure 7 depicts the stand of Figure 6 with a workpiece loaded for cutting of atenon.

Figure 8 depicts the stand of Figure 6 with the workpiece inverted.

Figure 9 depicts an exploded perspective view of a finished mortise-andtenon joint made by means of the present invention.

DETAILED DESCRIPTION Referring now to Figure 1D there is depicted a router guiding system for making mortise-and-tenon joints, in the form of template 1, according to the present invention. It will be noted that template 1 has two slots 3 and 5. Mortise slot 3 provides a guide for cutting mortises whereas tenon slot 5 is specially dimensioned to facilitate the cutting of complementary tenons.

Referring now to Figure 2 there is illustrated a router 7 for use with template 1. It will be noted that the router includes a base 11, cutting bit 9 which in operation rotates and a guide portion 13 which remains stationary. The guide and cutter are shown in plan view in Figure 3 where it will be noted that the radius of the cutting bit is R2 and the radius of the guide is R1.

Referring now to Figure 4 the various dimensions of mortise slot 3 are drawn relative to R1 and R2. It will be noted that mortise slot 3 is of a width W and length L. Width W is constrained so that W=D+2 x (R1-R2) where D is the width WO 00/56508 PCT/AU00/00192 of the mortise to be cut and is constrained so that 2 x R25 D<5 4 x R2. It will be realised that D cannot be less than 2 x R2 as that would mean that cutting bit 9 would then be too large to produce the desired width slot. Alternatively if the slot mortise width is required to be greater than twice the cutting bit diameter, i.e.

4R2, then an inner fin of material would be left upstanding in the mortise slot.

While such a fin is undesirable it could be removed by application of the router or a chisel. The length L of mortise slot 3 is L=Z+2 x (R1-R2) where Z is the length of the mortise to be cut.

Referring now to Figure 5, the various dimensions of tenon slot 5 are shown relative to R1 and R2. It will be noted that tenon slot 5 is of width Th where Th=2 x (R2+R1)+D and is of length Y where Y=Z+2 x (R2+R1). Tenon slot 5 is filleted with a fillet radius of 2R2+R1.

Typically template 1 is manufactured from 8 mm perspex. It will be realised that slots 3 and 5 must be formed to a fairly high degree of accuracy in order that the resulting mortises and tenons will complement each other to a high degree. The inventor has had success in forming the slots by means of a programmable "CNC" milling machine or alternatively with a computer controlled laser cutter.

The use of template 1 and the formation of mortises and tenons according to the present invention will now be explained with reference to Figure 6. In Figure 6 template 1 includes two longitudinal mounting slots 13 for the purpose of securing the template to support arm 15 by means of bolts 17 and wingnuts 19. A vertical support 16 is connected to support arm 15. Vertical support 16 includes a slot in which runs one jaw of a vice grip 29. Beneath template 1 there sits a docking board 18 which includes a raised portion 20 having the same height as the thickness of template 1. Raised portion 20 is shaped to fit within tenon slot Referring now to Figure 7 a workpiece, is shown clamped to vertical support 16 by means of vice grip 29 for the purpose of forming a tenon. It will be noted that raised portion 20 ensures that workpiece 30 does not protrude into tenon slot 5. That the workpiece does not so protrude is preferred as it is desirable that the length of the tenons formed be the same as the depth of the WO 00/56508 PCT/AUOO/00192 6 corresponding morti se apertures. Accordingly, by ensuring that the workpiece enois flush with the upper surface of template 1 as shown in Figure 7 and also that work pieces to which tenons are to be applied are similiarly located flush over the mortise slot, it is possible to ensure that the depths of the tenons and mortises are the same. This of course being provided that the same length router bit is used for cutting the tenons as for making the mortises.

Referring now to Figure 8 it will be noted that template 1, and workpiece 16 have been inverted by swinging support arm 15 about pivot 23. A router may

N

now be guided around tenon slot 5 in order to form a tenon into workpiece 16 taking care to continuously exert force between guide 13 of the router ai d the oil 0 perimeter of slot Formation of mortises is entirely analogous to that of tenons except that because the mortise slot is always smaller than any workpiece into which a .0 09 mortise might be formed, there is no danger of the mortise workpiece protruding 0 1 5 into the mortise slot. Consequently a mortise slot docking station is not required.

With reference to Figure 9 a finished mortise-and-tenon joint, in exploded perspective view, is shown made by means of the previously described exemplary embodiment.

00)) It is also possible to produce angled tenons. All that is required is that r4 20 rather than clamping workpiece 30 to template 1 at 90', a desired angle must be ci made.

While the invention has been described with reference to a single 101 embodiment many variations are possible. For example mortise slot 3 and tenon slot 5 might be formed in separate templates. Furthermore the mortise and tenon slots might be of different shapes to those described however in that case it will be necessary to ensure that they are carefully dimensioned so as to form complementary parts.

it is also possible that rather than guiding the cutter guide of a router as has been previously explained, the base of the router might be guided in order to make the cutting bit of the router describe a mortice aperture or tenon. Such guidance could be provided by appropriately shaped fences around apertures through a plate.

WO 00/56508 PCT/AUOO/00192 7 It is also possible that rather than using a solid plate with slots formed into.

it another means for producing an edge suitable for guiding a router might be used such as a rigid meshwork with wire guides.

The essence of the invention lies in a router guiding system having a first means for guiding a router so that its cutting bit describes a mortise aperture and a second means for guiding a router so that its cutting bit describes a complementary tenon. Consequently the following claims are to be constructed in a broad sense and are not to be overly limited to the previously described exemplary embodiments.

Claims (4)

1. A router guiding system for the formation of mortise-and-tenon joints by means of a router, said router including a cutting bit and a guide for said bit, said router guiding system including: a) a first guiding means shaped so that upon moving said router in concert with said guiding means, and wherein operatively said guide is moved around within, and in contact with the peripheries of said guiding means a mortise aperture is described by said cutting bit; and b) a second guiding means shaped so that upon moving said guide in concert with said second guiding means, and wherein operatively said guide is moved within, around and in contact with the peripheries of said guiding •means a tenon is described by said cutting bit; wherein said first and second guiding means are formed o so that said tenon and said mortise are of complementary shape, wherein said first and second guiding means comprise respective first and second slots formed into a template, or templates, and P ~wherein said guide is of a radius R1 and said cutter is of Sa radius R2, said first slot being rectangularly shaped for o• the formation of mortise apertures of width D and length Z, said first slot having width W and Length L, where W=D+2 x (R1-R2) and L=Z+2 x (R1-R2) and said second slot is rectangularly shaped with filleted corners for the formation of tenons of width D and length Z, said second slot having width Th and length Y where Th=2 x (R2+R1)+D and Y=Z+2 x (R2+R1) said second slot being filleted with a fillet radius of 2R2 R1.

2. A router guiding system according to any one of claim 1 wherein said templates further include means for mounting to a 0stand.

3. A stand for mounting a template according to any one of claims 1 and 2, said stand including means for adjustably engaging said template, means for mounting a workpiece adjacent said template and means for rotating said template and said workpiece. AMENDED

4. A stand according the claim 3, wherein said means for mounting said workpiece is arranged to permit variations in angular orientation between said workpiece and said template. A router guiding system according to claim 1, further including a means for positioning a workpiece at a predetermined distance from a surface of said templates. 'a 45 a 2 c 0z. \y a. 4 S 'o Sa 'OS. OO