Routing An Edge Joint

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The first step in preparing any edge joint is to joint the edges of the mating boards. Suffice it to say here that this is an operation you can do easily with the router. Details arc found in "Jointing with a Router" on page 188. But you can joint most boards more quickly and accurately on the jointer, and there's no reason why you shouldn't use the jointer if you can.

But a router can help you do a special job of the fundamental woodworking task of edge-joining two or more boards to make a wide panel. A well-conceived and well-executed routed edge joint will virtually disappear—if that's what you want— because you can rout the mating edges to follow the direction of the grain, even though it meanders sinuously from one end of a board to the other. If you want the joint to stand out. you can make it do that in a special way. too.

I first ran across this technique about 15 years ago in a magazine

CUT PERFECT EDGE-TO-EDGE JOINTS WITH THIS ROUTER EDGE-JOINTING PLATFORM

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CUT PERFECT EDGE-TO-EDGE JOINTS WITH THIS ROUTER EDGE-JOINTING PLATFORM

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article. and I Ve rnn across explanations of it in several places since. The concept is to rout the mating edges as positive-negative images. Making the edges positive-negative images will allow them to join much better than simply trying to give them both perfect, smooth, straight edges. And making one edge the negative image of the other is what allows you to join them along a gentle curve as well as a straight line.

In brief, the technique is this: You damp a fence atop the first workpiece and. guiding the router base against the fence, trim about {A<> inch from the workpiece. Then you secure the second workpiece directly opposite the first. By guiding the router along the same fence—you haven't moved it—you trim the second workpiece and produce an edge that's a negative image of the first.

To execute the technique, you should have an edge-routing platform and matching fence, which you can easily make from a third of a sheet of good-quality K-inch plywood. I have one that's 4 feet long, sufficient for the work I've done using this technique. But you arc limited only by plywood's sheet sizes.

You can use whatever router you have, though a fairly powerful fixed-base machine is probably the ideal. A horse-and-a-half is probably minimum.

By all means, use a '/»-inch-shank bit. which will withstand side stresses better than a '/«-inch-shank bit. Naturally. the bit 's cutting edges must be longer than the workpiece is thick. A large-diameter cutter, Winch or more, will probably be less prone to vibrate under load than a '/i-inch-diameter (or smaller) bit. Because the tip speed is higher, the largc-diumetcr bit will give a smoother cut. too. And, of course, a shear-cut bit would be even smoother.

To make the platform,cut three 4-foot-long strips of Winch plywood. Cut one about 15 inches wide, the second one about 8 inches wide, and the last one about 5 inches wide. Glue the two narrower pieces atop the widest, as shown in Router Edge-Jointing Platform. The 2-inch-wide channel thus formed allows the bit to cut below the wood without marring the platform. It also gives all the chips and dust generated by the operation a place to go.

Cut a fence about 6 inches wide and about 4 inches longer than any-stock you anticipate edge-joining with the router. (Although the platform shown here is only 4 feet long, you can use it to position longer boards for router edge-joining. But regardless of the length of the platform, the fence must be longer than the workpieces.)

To use the platform, you have to rest it across sawhorses or some other support(s) that peiiuit you to clamp the work to both sides. A regular worldjcnch will probably be too wide for this. I trap the platform between the dogs on my router bench, which works fine.

To router edge-join two boards, set one of the two on the wider half of the platform. Set the fence on it. and adjust us position vis-a-vis the board's edge so you'll be routing away no more than inch of stock. Clamp the fence and the work to the platform. (If the work is narrow, you may need to shim the fence; just be sure both the work and the fence arc clamped so neither will move.)

Stand with the fence in front of you. Rout from right to left, pulling the router against the fence as you go. Check the edge. If it is less than smooth, square, and clean, shift the fence a tad and make a second pass.

When the first board is done, leave it right where it is. You don't move it or the fence. You simply position the second board along the opposite side of the platform, parallel with the first piece. You need a gap between the two boards that's Mo inch less than the diameter of the bit you are using. Got the gap set? Clamp down the second board.

Now the router will rest on both

The router is an excellent loci for preparing boards for edge joining. Using this simjAc rig, you can produce an almost seamless joint. Set the first board on the platform and clamp the fence to it. Trim the edge with a router

Router Techniques And Different Joints

(left). Then clamp the second board opposite the first. Guiding the router in the reverse direction along the fence, trim the second board (right). The two should mate perfectly.

The router is an excellent loci for preparing boards for edge joining. Using this simjAc rig, you can produce an almost seamless joint. Set the first board on the platform and clamp the fence to it. Trim the edge with a router

(left). Then clamp the second board opposite the first. Guiding the router in the reverse direction along the fence, trim the second board (right). The two should mate perfectly.

boards, but the bit shouldn't fit between them (if it does, cheek that gap again!).

To rout the second board, stand in the same place as before. But this time, you have to feed the router left to right. Pull it against the fence as you move it. Make the cut in a single, continuous pass. If you interrupt the cut for any reason, it's likely to be botched. You can rescue the work, of course, simply by finishing the cut. then shifting the second board slightly and making another attempt.

When the second board is machined. unclamp it—NOT the first piece or the fence—and pull it against the first piece. The two should mate perfectly. You may have to juke the second picce back and forth fractionally to get the two in sync, since there's only one correct alignment. A bump on the first piece should fit into a corresponding hollow in the second picce. That's because any imperfections in the fence arc telegraphed into the two workpieces differently—in effect, in positive form to one. in negative form to the other. When the two are in sync, they'll virtually merge together.

To help you line them up for gluing, slash a pencil line or two across the seam.

Of course, if the two pieces don f mate perfectly, it may be that you've failed to rout deeply enough. I'd try another pass on the seccnd board, and if that didn't curc the mismatc, I'd go back to the beginning and repeat the process.

To mate two boards in a curved joint, you must first roughly cut the

The amount of wood that's removed in a pass is very modest, and though the bit appears to be cutting two boards at once, it's not. On this pass, it is cutting only the board on the left. To limit the cut. the Inxtrds have to be set very carefully. You'll easily spend more time doing that than actually routing.

line on the workpieccs as well as on the lenec. The prime caveat is that the technique will not work with tight curves, because the bit is actually creating a different curve on each piece. The contour of one curve is offset from the contour of the other by the bits diameter. When you rout along a gentle curve, however, the two pieces should be sufficiently close to fit together nicely, forming a clean joint. Using a small-diameter bit minimizes the offset.

Just be forewarned: The more curve you use, the less perfect the fit. For a good glue-up, you probably should deviate no more than about 5 degrees off a straight line. Use your platform as a guide. Its channel is only 2 inches wide, so your curve can't range much more lhan V^of an inch off a baseline. (See "Edge-Joining along Curved Lines" on page 158 for a technique that allows you to join two boards perfectly along almost any curve.)

Lay out your curvc, transferring it to the first workpicce and the fcncc. After cutting these two pieces with a saber saw or on the band saw, use one to trace the curve onto the second workpicce. Remember that this second piece must be the reverse of the first, not a duplicate.

Set up the first workpicce and the fence on the platform, much as if it were a straight joint. Rout the piece. Then position and rout the second workpiece.

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