If there’s one router jig that I hope you build, it’s this one. This one is the easiest to use, simplest to set up, and consistent in its results. I’ve used this on all kinds of boxes and clocks. I’ve taught it for a class and everyone who’s made one feels the same way.
It’s genius in its simplicity. One part of the joint is routed on one side of the jig. The mating “negative” part of the joint is cut from the other side. No adjustments are necessary between each step.
JIG COMPONENTS.
A thick plywood beam makes up the structure of the jig. The beam rests on a base that extends out the ends so that you can clamp it to a surface. A stop on one end provides registration of the workpiece.
A replaceable hardboard backer faces each side of the beam to prevent tearout. A T-track in the top of the jig accepts keys that are “key” for creating the finger joints. The keys can be made from plywood or hardwood. And their size doesn’t matter. The keys are held with short screws and square nuts. Keep an Allen wrench close by.
JOINT GEOMETRY.
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| Pattern bits in several lengths and diameters increase the jig’s versatility. |
The arrangement of the keys determines the look of the joints. The length of the keys is important. A pattern bit traces around the keys. The bearing stops against the butt end of the opposing key to avoid routing into the jig’s beam. Here’s the genius. Each key is responsible for the shape of each side of the joint, this is why the width of the keys doesn’t matter. You can make irregular and variable spaced fingers. If you can follow a template, you can make eye-catching finger joints.
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|The plans suggest a few sizes for keys. But you feel free to make a set in any size a project requires. I keep a box full of extra keys, screws, and nuts.|
SETUP
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| Slide each key into place. The first one should be snug against the end stop. Tighten each one sequentially with an Allen wrench. There’s no need to squeeze them tight. |
This leads right into the setup of the jig. Come up with the arrangement of keys you’d like for the project, then slide them onto the T-track. The first one tucks in snug against the stop. Tighten it down. Repeat, alternating the direction of the keys. Make sure the keys are snug (not jammed) before cinching them down, as shown. At the end, slide one last key on the jig. The size doesn’t matter. Though I would choose a wideish key. Its role is to provide support for the router at the end of the joint.
WORKPIECES
Arrange the project parts how you want them to be. The width of the parts should match or be a hair wider than the arrangement of the keys. I use a triangle to mark the top/front edge of all my parts.
Draw or scribe a baseline for the finger joints around the ends of the pieces. You can aim for a flush fit or create fingers that protrude at the corners. I use the bottom/back edge of the parts as my reference edge. This means the parts will be aligned and flush when assembled. So when you clamp the parts into the jig, the triangles will be on the outside.
Narrow parts can be held with a single clamp. Wider parts with two. There you go. The jig is set up for the first cuts.
BITS
The pattern bit needs to be set for two conditions: first, the end of the bit is even with the baseline (matches the thickness of the parts — for a flush joint). The second condition is that the bearing on the bit engages with the keys and the cutting edge will cut all along the joint surfaces.
Depending on the thickness of the parts you work with, this may mean you need to get pattern bits with shorter cutting edges. I keep a few sizes of pattern bits to accommodate a variety of thicknesses, as shown on the previous page.
ROUTING
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| To rout the mating portion of the finger joints, all you need to do is turn the jig (and the beat) around. The orientation of the keys forms the pattern for the bit. Be sure to keep the reference edge against the end stop. |
Let’s fire up the router and make a corner. Work from left to right. Make a light skim cut across the face of the piece before you dive into the cut. This prevents tearout. Trace along each of the keys. Be sure that the bearing contacts the end of the key at the back. After routing one end, flip the piece end for end. Remember to keep the same edge against the stop. Repeat the routing for all the similar parts.
OPPOSITE SIDE.
Turn the jig around. Again, clamp the adjacent workpiece in the jig, with the reference edge against the stop. The routing is the same but the pattern is reversed. When you’re done, you can test fit the parts. Yup, they fit.
EXTRA BACKERS.
The hard-board gets cut up with each key pattern. Flip the backers around to find a clean edge. Then make a few extras to keep on hand.
I’m a tinkerer, so I’d understand anyone that wants to make changes to the jig. There isn’t much that could be improved in my opinion. But here are a couple options: First, the plans indicate a few key sizes. They’re fine, but the nature of the jig means you can make new ones whenever you want and to suit the project at hand.
The second is you could make the jig wider to accommodate larger case pieces. This makes it more unwieldy, but if that’s your jam, go for it.
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|The fingers fit snug right from the jig. No fussing required.|
