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WOODWORKING

It's Simple: Choose Joint to Suit the Job

June 21, 1997|From Associated Press

Have you noticed that once a woodworker learns how to make tightfitting dovetail joints, they begin to appear on everything?

Woodworkers aren't immune to the if-you've-got-it, flaunt-it syndrome. However, the real pro will tell you to choose your joint to suit the job. And in many cases, the direct approach is not only faster and easier, but just as strong as the fancier, more skill-intensive solution.

The simplest way to join two pieces of wood is to cut them to size, apply a little glue to the mating surfaces and put the assembly in clamps until the glue sets. Unfortunately, this method doesn't work well if there's any end-grain involved.

End-grain joints require reinforcing, usually with dowels or splines, so the glue joins the pieces through adequate long-grain contact.

As it turns out, dowels and splines are also handy for aligning and reinforcing ordinary edge-to-edge joints. In combination with milled joints such as tongue-and-groove joints and glue joints, you're prepared to solve a wide range of joinery problems. Best of all, you can make most of these joints quickly and accurately using ordinary hand and power tools.

Here, we'll look at some techniques:

* Basic butt joints: When used correctly, today's glues are stronger than the wood itself. Therefore, when laminating stock to produce wide panels, there's a good argument for leaving out any type of reinforcing.

The secret to a successful edge-to-edge glue joint is perfect contact along the entire mating surface. Begin by laying out the boards and marking them as they're to be assembled.

If you have a jointer, joint each edge. Check for fit by lacing the mating surfaces together and looking for any light that passes through the seam.

To fine-tune a joint, or do the job entirely by hand, fold two adjacent boards together and hold them in your vise so both mating surfaces can be planed at once. Then, true the edges with the longest plane you have. Because both edges are planed together, slightly out of square planing is negated when the boards are unfolded and joined.

To keep the boards aligned when gluing them together, sandwich straight boards on both ends of the assembly and clamp. Then apply clamps across the assembly. Alternate these clamps above and below the panel to equalize the pressure and reduce any tendency the assembly has to cup.

* Doweled joints: Using dowels in a butt joint increases the mechanical resistance to lateral stresses and maintains alignment when gluing the boards together. While it's a popular alternative to simple butt joints, keep in mind that it often creates a cross-grained assembly.

In edge joints, avoid using dowels longer than about 1 1/2 inches. Otherwise, the dowels may actually force the joint open if the wood dries and shrinks. Always make the dowel holes slightly deeper than necessary and either buy or make grooved dowel pins so excess glue can escape.

To add dowels to an edge-to-edge joint, first place adjacent boards together and use a square to mark center lines on both edges. Use a doweling jig to ensure that the holes will be square to the edges and at a uniform distance from the work faces.

Some doweling jigs are self-centering. If you're using the non-centering type, be sure to reference one side of the jig with a designated work face on your stock to ensure that adjacent faces will be aligned. Use a depth stop or piece of tape wrapped around the drill bit to gauge hole depth.

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