Sit tight

It takes a stubby drill driver or a right-angle attachment to install a pocket screw between a chair’s parts. Save space by inserting the bit directly in the chuck rather than in a magnetic bit holder. Image credit: Devon Jarvis
Date:23 February 2012 Tags:, ,

Q At least half of the wood chairs we own are wobbly. We’ve tried every adhesive we can think of to fix them – white glue, yellow glue, epoxy, polyurethane. Nothing seems to work. What do you suggest we do?

A Glue alone won’t work. It’s natural to think that it would do the job – like most homeowners, you squirted some glue into a loose joint and hoped for the best. But unfortunately, applying a thick glob of adhesive is actually counterproductive. Wood adhesives work best when you apply a thin film of the sticky stuff to both sides of a joint, then use pressure to force the parts together. Furthermore, you almost always have to rebuild the joint, reinforce it, or disassemble it and remove adhesives from previous repairs to get it to fit properly.

Let’s take a closer look at this. For a chair to be moved around easily, it has to be lightly built. Yet the loads a chair accommodates are severe. A chair may weigh 4 to 6 kg, but it has to support a person 10 times its own weight (usually more). And that person is a highly dynamic load. He or she may sit, stand, twist or shift on the chair, putting its joints and parts through strenuous cycles. Compare that with cabinets, chests of drawers and dressers.

This furniture is over-built relative to the weight it holds. A chest or dresser can easily weigh 25 to 50 kg, yet hold less than 15 kg of clothing. Aside from sliding drawers, for most of the time, the load is stationary. You can see why chair joints fail, sometimes catastrophically.

One relatively easy solution for chairs that have only one loose joint is to bore a pocket hole in a discreet location, spread a thin film of professional-quality wood glue on the loose parts, and then drive a pocket screw to lock the joint together. I’ve done this to a couple of chairs in my house, and I’ve been pleased with how well the repair has stood up.

This technique won’t work if there’s adhesive from a previous repair on the joint; it creates an undesirable surface on which to spread new glue. And this works only for chairs with parts that are thick enough or wide enough to withstand the amount of wood that is removed when a pocket hole is bored. Finally, don’t use this method on an antique; you could diminish its value.

With a chair that has a number of severely loose joints, label all the parts with masking tape, then disassemble them using a clamp with a reversible jaw, known as a spreader. After you have the parts separated, carefully scrape away the dried adhesive, then repair, rebuild and reinforce the joints. Finally, reassemble the chair using professional-quality wood glue. If you’re not an experienced woodworker, take a course at a community college or craft centre before undertaking this project.

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