Dovetail Jigs - Canadian Woodworking Magazine

Router Basics: Dovetails are the hallmark of finely crafted furniture; they are attractive, strong and can elevate a project from the average to extraordinary. Their limiting factor for most woodworkers has always been the level of skill required to execute them.

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Dovetail Jigs



Illustration by James Provost

While there is obviously a role for hand cut dovetails, particularly in custom furniture, there is likewise a time and place for machine cut dovetails. In a kitchen with 30 drawers there would be 120 corners to cut. That’s a lot of chisel and saw work. While it might take you three or four days to cut all the joints by hand, you could easily cut them in a day using a dovetail jig.

There are quite a few dovetail jigs on the market. When most woodworkers think of a dovetail jig, what comes to mind is something similar to the design of the legendary Leigh D4. With this design, the jig is clamped to your workbench, the work piece is clamped to the base of the jig, and a finger guide placed on top of the work guides a hand held router equipped with a bushing. Jigs like the Leigh cut both through and half blind dovetails and those equipped with moveable fingers enable you to cut variably spaced dovetails and with alternate templates, other decorative joints. There are several simpler jig designs on the market as well, which typically cut only through dovetails (see Other Dovetail Jigs sidebar).

In this article we’ll look at the top four dovetail jigs on the market: the classic Leigh D4R, the new Leigh Super Jig, the newly redesigned Porter Cable OmniJig, and the recently updated Akeda BC24. These are full-featured dovetail jigs; while they are not what you might consider budget models, they offer good value to the user that prefers not to come up against limitations in what their tools are capable of doing. Though not inherently dangerous, there are several safety precautions you should observe to avoid personal injury or damage to the jig (see Dovetail Jig Safety sidebar).

These jigs share similar features: a base with a clamping mechanism that the material is mounted onto, a guide finger assembly, and a guide bushing and bit for the router. The finger assembly provides a guide (fence) that the outer edge of the guide bushing follows, moving the router bit along the correct path to cut the joint. Except for the Akeda, the guide finger assemblies for these jigs rest on a set of arms that project from either side of the jig, and the assembly is slid onto these arms and then must be positioned correctly for each of the various joints you can cut.
 

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Leigh: Super Jig
 

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Porter Cable Omnijig
 

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Akeda: BC24
 
The Operational Concept
All four jigs use a finger assembly and guide bushing. No matter which system the jig employs, each type of joint will require a different guide surface. On the Porter Cable and Leigh jigs, the finger assembly is one piece, which is set and moved as a single unit with the pin and tail spacing remaining fixed as the template is repositioned for the various types of joints. Each of the templates is used in one of four positions depending on the cut you are making; the templates are simply rotated end for end as well as being flipped upside down. This allows access to four different guide surfaces. The Akeda implements the same concept in a slightly different manner by using individual fingers that are snapped into an indexed guide rail.

The guide bushing is equally important to get a tight fitting joint. It is the guide bushing that runs along the guide surface on the finger assembly and guides the router bit. These four jigs use the ubiquitous Porter Cable guide bushing (which are supplied with the jigs). If your router won’t accept these bushings then you will need to contact the jig or router manufacturer to purchase an adaptor to fit your router. When you install the bushing, be sure that it is securely fastened to the base of the router; you don’t want it working loose.
 
Leigh D4R and Super Jig
The D4R and Super Jig are the latest designs to evolve from the venerable Leigh D1258R. In operation, these two jigs are very similar. The base of the Leigh D4R is CNC machined from a single extrusion of aircraft grade aluminum with all side stops and registration edges machined in place. By machining all of the surfaces on a CNC machine they are guaranteed to be straight and square. The extrusion is then capped at each end with precision cast end caps. The arms that support the finger assembly mount to these end caps and can be easily raised or lowered using large knobs on either end. The clamping surface on the extrusion has been machined to provide a non-slip surface. The Super Jig was designed to be a more affordable jig for the non-professional woodworker. To reduce production costs, Leigh reduced the amount of time the base spends on the CNC machine. The metal end caps and the side stops on the Super Jig are made of nylon and must be installed by the end user. As well, the machined clamping surfaces have been replaced by an applied abrasive surface.

Both jigs feature a guide finger assembly that allow the fingers to be placed anywhere along the length of the work piece. This enables you to use any dovetail spacing that best suits the width of your stock and the scale of your project. The maximum stock width on the D4R is 24". There are three models of the Super Jig, in 12", 18" and 24" widths. The fingers on the D4R are split lengthwise allowing you to create tails of varying widths; this feature isn’t used by most casual woodworkers and was dropped from the Super Jig as a cost cutting measure. A bonus feature on the Super Jig is that the single piece adjustable fingers provide the correct geometry to allow you to rout finger (or box) joints on the same guide finger assembly.

When using the Leigh jigs, the guide finger assembly can be mounted in four different positions by rotating it or flipping it end for end. On both ends of the fence, a graphic indicates the mode you are working in. The active mode will always face the operator and be upright, and the inactive mode will be displayed upside down from the operator’s position. A graphic of the joint being cut is displayed which makes it easy for the user to ensure the fingers are in the correct orientation for the joint being cut.

The finger assembly moves back and forth on the two support arms and is positioned using registration lines that have been machined into the arms. For the various operations, moving the finger arm forward or backward on the arms controls the fit. Router tolerances, runout, and guide bushing tolerances make it difficult to cut a perfect fitting joint the first time, so for each combination of bit and guide bushing combination, you need to make a test cut to fine tune the fit. After working through the process to arrive at the perfect setting, record it in the operators manual for future reference. It’s a good idea to make a couple of set-up pieces and label them with the router bit number. To set the bit depth with the same bit in the future, clamp the set-up pieces into the jig and use them as guides.

The D4R uses a standard 7⁄16" guide bushing for all cuts. The bushing that ships with the Super Jig (the e-bush) has been redesigned slightly to provide a fine adjustment mechanism when cutting box joints. The e-bush is elliptical in shape, and there are a series of numbers around the outer edge on one quadrant. When the bushing is set to the maximum setting of #10, the bushing functions as a standard 7⁄16" guide bushing. Each increment on the e-bushing provides a change of .002", which makes it simple to attain perfectly fitted box joints.

The Super Jig comes with a nylon spacer that serves two functions. It is used to set an even spacing between each finger, and then when routing the second board it snaps into a holder on the clamp mechanism to off-set the second board the correct distance from the first one. This is a handy little bonus feature that doesn’t require the purchase of additional guide finger assemblies. When the bushing is used to cut box joints, the e-bush is set to the middle of the scale at position #5. As the outer diameter of the bushing gets narrower, it allows the router to remove more material from between the fingers, as the bushing gets wider, router travel is more restricted and consequently, less material is removed.

Both Leigh jigs easily cut sliding dovetails. A plastic insert that is attached to the front of the guide fingers provides a guide-way for both the tail and socket pieces.

Getting a perfect fit on a sliding dovetail is a matter of trial and error but the process is laid out clearly in the manual. To adjust the fit on a sliding dovetail, the socket is first routed in one pass and then the tailpiece is prepared. The initial cuts on the tailpiece are made to produce a tail that is intentionally larger than required which is then reduced in width with subsequent passes until a perfect fit is achieved.

Dust collection has always been an issue with dovetail jigs. An optional accessory, the Leigh Vacuum Router Support (VRS), connects to any shop vacuum, and serves both to siphon dust away from the jig and to provide additional support at the outer front edge of the jig. This is the spot that the router will tend to want to tip forward and the additional surface of the VRS provides an edge to support the router. A pair of wire arms that attach to either side of the router move the collection chute back and forth as you use the router, and when the cut is complete, the router can be quickly parked on the right side of the jig without the need to lift it off the jig and place it on your bench. I was skeptical about the efficiency of this accessory, but in use it has far surpassed my expectations and I consider the VRS a must have accessory. It really does capture almost all of the material the router generates. The convenience of being able to park the router to the side really makes production work a breeze.
 

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Leigh: Infinitely variable guide fingers
 

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Leigh Superjig: Through dovetail scale
 

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Leigh: Through dovetail pin mode
 

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Leigh: Through dovetail tail mode
 

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Leigh: Sliding dovetail socket board
 

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Leigh: Sliding dovetail tailboard
 
Porter Cable OmniJig Joinery System
The newly redesigned OmniJig has a lot of improvements over the previous version. The 24" model (a 16" model is also available) comes in at a substantial 43" wide and weighs in at a robust 66 pounds. The bulk of this is the aluminum base, which has been machined with a textured non-slip surface where the work pieces are clamped, ensuring that they remain solidly in place during the routing process. While the OmniJig incorporates many of the same features found on the Leigh D4R jig it has several distinctive features of its own. The clamping  mechanism is very nice, in that once it has been set for the thickness of the material you are working with, it is engaged by simply pulling one lever. As on the Leigh, the guide fingers are infinitely adjustable. The finger guide that slides onto a pair of arms mounted on the jig is perfectly positioned by an innovative improvement over the Leigh. The OmniJig includes several different guide stops that are placed into a hole in a wing on either side of the jig and this accurately locates the finger assembly correctly on the arm. It also features factory preset depth stops to help you set the bit depth. Most of these are located in the router depth pod, a box containing 12 stations to set the heights for twelve different cut types. The settings in the pod are used to set the bit depth for single-pass half blind dovetails, sliding tapered dovetails and four user defined settings. This box is mounted to the back of the jig where it is readily accessible while keeping it out of the way.

There are two other depth stops located on the left side of the jig under the guide finger assembly. These are used to set the bit depth for through dovetails. They are fine tuned right from the factory to provide perfect results when used with the proper bit and following the procedure as outlined in the manual.

There are several additional guide finger assemblies planned for this jig, one for small dovetails and one for finger joints. There is also a mortise and tenon attachment in the works that will allow you to cut mortise and tenon joints of various sizes.
 

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OmniJig: Self aligning template
 

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OmniJig: Setting bit depth
 

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OmniJig: Dust chute helps support router
 

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OmniJig: Setup for tails
 
Akeda Jig
The Akeda BC24 requires few adjustments and is very intuitive to use. Unlike the previous jigs, the guide fingers on the Akeda snap into an indexed rail mounted to the jig. There are three types of guide fingers; through dovetail pin guides; half blind pin guides and tail guides. Also included are Tail Guide Spacers that you cut into strips and snap in between the tail guides for sliding dovetails; this prevents routing in the wrong places. The guide rail these snap into is indexed in ⅛" increments, which means that you can snap the fingers into the same location for precise, repeatable cuts. After designing your layout, place a small pencil mark on the rail behind the fingers to note their location. When it comes time to switch to one of the other guide fingers to complete the cut, line the new fingers up with the pencil mark, snap them in and rout the joint. If you find the joints are slightly too tight or slightly too loose, replace the standard guide bushing with one of the optional oversized (.442") or undersized (.434") to correct the fit.

This simple system reduces the bulk of the jig but it also means that for your joints to be laid out evenly, your material will have to be sized in ⅛" increments. This is a small sacrifice when you consider the simplicity this brings to the jig. The method of clamping the work piece is different on this jig. The other three jigs clamp the material either vertically or horizontally against the body of the jig. The Akeda uses three different clamping positions – against the jig horizontally, vertically between the clamp bar and the jig body, and vertically between the clamp bar and the front of the jig. These three positions will line the board up with the correct portion of the guide fingers.

The Akeda features a clear window across the front of the jig which remains in place for all operations, other than sliding dovetail sockets. It keeps material from blowing back at the operator and focuses the debris into the snap-in dust collector. A separate dust collection kit is available on its own, or as part of the complete accessory package, and like the one on the Leigh jig, it is a must have accessory. I use this jig hooked up to my shop vacuum and it catches virtually every speck of dust the router kicks up. To rout sliding dovetail sockets, the clear window pops out so the board can be mounted horizontally through the opening. The window is reversible as well, which narrows the opening, concentrating the suction from the dust collector – handy if you are using a shop vacuum instead of a dust collector. To rout narrow boards, I place a strip of wood against the opening on the other end of the jig to increase the pick up at the active end. The front of the jig provides a second surface on which to register the router. This is very helpful as it keeps the router perpendicular to the jig and allows you to park it off to the right when not in use.

The Akeda jig uses proprietary router bits with 8mm shanks. They require the use of a router with a ½" collet and a reducer, or a router with an 8mm collet. An 8mm shaft contains twice as much material as a ¼" shaft with a corresponding increase in strength and rigidity and this results in a smoother cut. The bits, coated with Teflon to help reduce pitch build up, come in a variety of sizes and angles to suit the stock thickness you are using.

When cutting sliding dovetails, the adjustment process is the reverse of the Leigh jigs. Rather than cutting the pin board to fit the tail, the socket is enlarged to fit the tail board. Again, this is a matter of trial and error until you have achieved a perfect fit. Sliding dovetails can be notorious for seizing before they have been driven fully in place and I’ve developed a system that I use with the Akeda to slightly taper the socket. I place a couple of small pieces of painter’s tape on the front edge of the work piece where it hits the side stop at the back of the jig. This angles the material just enough to provide additional clearance for the glue as you slide the pieces together. There is a small edge on the end cap that a small piece of metal could be clipped to as an alternative to the painter’s tape.
 

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Akeda: Guide fingers snap into indexed guide rail
 

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Akeda: Half blind dovetails
 

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Akeda: Installing guide fingers
 
In the Final Analysis
These four jigs are capable, professional quality products. They all deliver what they promise and are exceptionally well made. The OmniJig would be ideally suited to a professional shop that has the space for a machine of this size. The integrated depth stops make it easy to adjust the finger assembly and get into production without wasting time and material to cut a test joint. The Leigh jigs are superbly designed and manufactured (in Canada) and will provide the woodworker with the capacity to create a wide range of dovetail based joinery, but in a smaller package than the OmniJig. The Super Jig provides most of the same functionality as the D4R, but changes were made in materials and the manufacturing process to bring this jig in at a competitive price point that would appeal to budget conscious woodworkers. The Super Jig also allows you to cut 5⁄16" and ⅝" box joints with the same guide fingers. The Akeda is the result of the designer taking the original concept of a variable pitch dovetail jig to the next level. By giving up some minor flexibility, in that you need to work within the ⅛" increment structure provided by the guide rail, you get a compact easy to use jig with the ability to cut finger joints.
 
Dovetail Jig Safety
• Read both the router and jig instruction manuals before using them.

• Wear safety glasses and hearing protection.

• A smaller fixed base router will be safer and easier to control than a larger top-heavy plunge router. This becomes especially noticeable as you cut along the front edge of the jig where there is typically minimal support for the router.

• Avoid using a plunge router as there is always the possibility of accidentally releasing the plunge lock. This will cause the bit to rise up and contact the bushing, damaging the router bit, bushing, and finger assembly.

• After installing a bit in a router fitted with a guide bushing, spin the bit manually to be sure that it is not contacting the inside edge of the bushing.

• Do not place your face level with the spinning bit; establish a point of reference on the router and the jig which will allow you to operate the router while looking down from above.

• Keep the router level on the guide finger assembly; allowing the router to tilt forward when routing near the edge of the guide finger assembly will ruin the joint.

• Ensure the bit has stopped spinning before you lift the router from the jig.
 
Troubleshooting and Tips
• Tear-out usually occurs on the top left corner where the bit exits the wood as a result of short grain and a lack of support. When possible, back up vertically clamped boards with a horizontally clamped back-up board, which can be left in place for successive cuts.

• In most situations you move the router from left to right, with the bit cutting upwards out of the wood. However, when making your first cut in side grain, use a shallow ‘climb cut’, by moving the router right to left (see “Routing Basics Part II”, Aug/Sept ’07, Issue #49). The router will have a slight tendency to move out of the cut and pull the router along the edge of the work, but with a little practice, making a climb cut on the outside surface will give you a perfect edge without tear-out.

• Ensure your router bits are sharp, and set your router speed between 18,000 and 24,000 rpm for optimal results.

• When test fitting dovetail joints, keep the pieces square to each other. If the joints are wiggled to assemble or separate them, the fibres will be crushed and the fit will not be as precise. The joint should come together easily; a firm push with the smaller joints, and a light tap from a mallet for larger ones.

• A router bit for half blind dovetails has a specific depth that it is designed to cut at, and must be set precisely. Refer to your manual for the depth. Only very minor adjustments are possible to fine tune the fit. As the angle on the dovetail bits increases, the amount of adjustment available falls considerably; adjusting the depth by the same amount on a 9º bit will not provide as great a change as the same adjustment made on a 20º bit.

• When making a joint that you are likely to repeat in the future, make a spare sample of the joint. To recreate the joint, clamp the spare into the jig and use it to set the finger location and router bit depth.
 
Other Dovetail Jigs
There are several other approaches to dovetailing with a router. The first dovetail jig designed for use on a router table was the Keller jig (kellerdovetail.com). It features a machined guide finger assembly that is fastened to the work piece; the dovetails are then cut on the router table. This same process is used by the Woodline Route-R-Joint system (woodline.com). The Woodline system also allows the creation of various joints in addition to dovetails. Like the Keller jig, joints are cut on the router table.

The Craftex CT052 is a budget level jig ($99) that does both through and half-blind dovetails (busybee.com).

The Prazi chessmate dovetail jig (praziusa.com) is fastened to the work piece and the joints are cut with a hand held router. The jig consists of a guide with several different inserts that are mounted to a layout stick you make in the shop. To make the layout stick, you mark out the center of each tail on your work piece, transfer these to the layout stick, and then use your table saw to cut a saw kerf on each mark. A ridge on the jig will then register in this kerf to locate the jig correctly. The advantage to this system is that you can dovetail a piece as long as your guide piece.
 
Related Articles:
Wood Joinery: Dovetails
Jun/Jul ‘04, Issue #30
Canadian Tools: Akeda Dovetail Jig
Jun/Jul ‘03, Issue #24
 

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RESOURCES:
"Wood Joinery: Dovetails", Jun/Jul '04, Issue # 30
"Canadian Tools: Akeda Dovetail Jig", Jun/Jul '03, Issue #24


MICHAEL KAMPEN
Michael Kampen