How to make the perfect dowel joint
If I had to choose just one method to connect project parts for the rest of my woodworking career, the dowel joint would be it. Strong, precise, hidden and versatile—the only danger is that dowel joints seem so simple at first glance. Simplicity makes it easy to underestimate the importance of getting key details correct, and then trouble sneaks in. Alignment of holes, precision of dowels, tight joint assembly—these are the essentials behind every perfect dowel joint. Get the basics right and the dowel joint will become one of your all-time favourites too.
Perfect dowel joinery happens only when the drill bit making the dowel holes is guided mechanically, which is why dowelling jigs were invented. They’re metal tools that guide the angle and location of drill bits in a handheld drill as they bore into wood. There are many dowelling jigs on the market, but the best I’ve used so far is designed and made in Canada. Dowelmax (dowelmax.com; 250-764-1770) is the product of the father-and-son team of Jim and Mike Lindsay. You also can use a drillpress to make dowel holes, either directly or by creating your own jig from hardwood blocks.
Some dowelling jigs make it easy to locate mating pairs of dowel holes across a joint, but sometimes you need the help of dowel centres. These round, aluminum buttons have ends with small, central spurs. Push a dowel centre into each hole drilled on one side of a joint, bring the mating pieces of wood into alignment, then push the two pieces together tightly. The spurs mark the centre of the holes required on the other side of the joint.
The diameter and length of dowels for joinery matters, and cutting your own short dowels from a long rod isn’t the best way to get things right. Run-of-the-mill dowels are usually smaller than specified and not precisely round. They are also typically made from tropical hardwoods that aren’t all that strong. Although I’m a purist on some woodworking matters, I do opt for ready-cut “dowel pins” every time. Besides being precisely sized, truly round and made of strong wood, dowel pins also have grooves pressed into their sides.
These grooves are called “flutes” and although they obviously retain more glue along the sides of the dowels during assembly, there’s more: the wood that was compressed to form the pins with flutes in the factory also swells in contact with glue after joint assembly, making for a stronger joint.
When you’re working with wood that involves the edges of boards, choose a dowel diameter that’s roughly one-third to one-half the overall thickness of the wood, with a dowel length that’s roughly twice the wood’s thickness. If you’re joining 3⁄4″-thick x 21⁄2″-wide cabinet door frames, for instance, 5⁄16″- or 3⁄8″-diameter dowel pins that are 11⁄4″ to 11⁄2″ long are ideal. I like 1⁄2″-diameter dowels when working with 11⁄2″-thick wood. For projects involving 1⁄2″-thick parts, 1⁄4″ dowels are perfect. Traditional timber frames are held together with 1″-diameter dowels, no matter how big the timbers are.
When it comes time to assemble a dowel joint, always clamp up the parts fully without glue first to see if any dowel holes have been drilled too shallow. Dry-fitting also lets you figure out exactly which clamps you need and how they should be adjusted. You’ll appreciate the extra speed later: joints need to slide together quickly after the glue is applied because the dowel pins will start to swell. You’ll get the best results if you work glue onto the sides of each dowel hole with a toothpick and apply a little glue onto the surface of each dowel with an inexpensive plumber’s flux brush.
The tool world has a tendency to make woodworking seem more complicated than it is. There’s a gadget for everything, and as these luxuries gain the status of necessities, skills become less important. Dowel joints are a simple option that’s classic enough to require skill, yet advanced enough to work really well. Can you see why I like dowel joints?