Chairs need to support people; tables need to support dinner, or computers and books, or vases filled with water and flowers; cabinets need to hold their content; and, doors need to support the weight of their woods. This is basic to the woodworking projects we tackle in our home shops.
The strength of the pieces we build comes from the joinery, and when it comes to joinery, we have choices. We can go old school and keep metals out of the joints – mortise and tenon, dowels, biscuits; or, we can use more modern methods and use metals – nails, screws, pocket hole joinery.
Opinions vary on the various levels of strength each method of joinery provides. Traditionalists argue that the tried and true over centuries mortise and tenon joinery provides the strong joint your project needs. Modern tool jockeys will counter that more modern metal joinery like pocket hole joints give you all the strength you need for any project.
While Obsessed Woodworking is not a testing laboratory and does not have the equipment to measure and compare strengths, we have done some research and have an idea on joint strength. We also respect the old ways very much and marvel at the beauty of nailless/screwless construction. Have you ever seen the magic of Japanese construction without metals?
In the same respect, we also respect ingenuity and the cleverness of modern techniques, and as we have written of in past articles, we love the ease and quickness of pocket hole joinery facilitated by the Kreg jig invention a little over 30 years ago, and the mortise and tenon joinery made easy by the Festool Domino.
We’ll break down these two methods of joining two pieces of wood – dowels and pocket holes – and share some of our research with you. We’ll close with some final thoughts on traditionalism vs modernism when it comes to joinery.
Don’t confuse dowels for joinery and lengths of dowel rods. They are two different animals. While dowel rods are smooth-surfaced, joinery dowels are ridged in a thread-like groove.
This groove plays an important role in ensuring the glue used as a part of the joinery does not pool at the bottom of the dowel holes in the pieces being joined. Instead, the glue will travel up the groove as pressure from clamping is applied. The surface of the groove increases the surface area glue can adhere to in the joint.
Doweling jigs are easy to use, and every woodworking shop has a power drill. A good doweling jig will run you around $75. These are the only tools you need for dowel joinery. Dowels, glue, and clamps complete the list of necessities for the task.
Doweling jigs are self-centering, an important consideration, and many models come with an integrated clamping mechanism for stability while drilling. The joint spots are measured and marked, the jig is clamped into place, and the holes are drilled to the proper depth in both pieces being joined to match the dowel size being used.
Glue is applied to the holes and the dowels, they are inserted into one piece, and then the pieces are joined dowels to holes in the second piece. Clamps are applied to hold the pieces together while the glue dries and the joint is set. The clamping time is based upon the glue or epoxy you have chosen to use. Because the doweling jig is self-centered, the workpiece surfaces will align smoothly, and when the glue is dried and the clamps removed, you have a solid joint.
Here’s a very decent video on dowel joinery.
Pocket Hole Joinery
We’ve written about pocket hole joinery many times in past articles, including the piece published just before this one was written. The story of pocket hole joinery really begins in the late 1980s with the invention of the Kreg jig by Craig Sommerfeld.
The Kreg jig is well-known in woodworking circles, and we use one ourselves at Obsessed Woodworking. The jig facilitates angled holes being drilled in one of the workpieces being joined, the pockets, and pocket hole screws are then used through the holes to turn into the second workpiece. The flat washer head of the pocket hole screws butts up against the end of the hole drilled by the special bit, and follows the pilot hole into the second piece.
The screw pulls the two pieces together, entering the second workpiece deep enough to reach its center point, and a strong joint is created. Pocket hole screws come in two types of threads, and the one you choose is determined by the type of wood you are joining – one for softwoods and one for hardwoods. While glue could be used, pocket hole joinery proponents believe the screw is enough.
You can read up on pocket hole screws here in one of our past articles. Also, here’s a pocket hole joinery basics video.
Comparison of Dowel Joinery and Pocket Hole Joinery
Dowel joinery offers positive alignment in both directions because of the self-centering jig, and matching them on each piece being joined is easy with accurate measurements. There is no visible sign of the dowels; there is only the seam of the two workpieces joined.
However, dowel joinery requires clamping to allow glue to dry, and is therefore a slower method of joining workpieces.
Pocket hole joinery is both easy and fast, and requires no clamping. When the screws are tightened, the joint is created, and you are ready to move on to the next task in your project.
However, pocket hole joinery does not guarantee positive alignment of the workpieces as dowel joinery does. There is also the matter of the pocket holes, although you can use both wood and plastic pocket hole pegs to fill the drill holes. Depending on the project, though, the holes may not be in a place where they can be seen, like the inside of a cabinet, or the inside of a table apron, or the backside of a picture frame.
Comparative Strength of Dowel Joints and Pocket Hole Joints
We’ve used both joinery methods in our home woodworking shop, and like each of them. Pocket hole joints are easy and quick because of the Kreg jig; dowel joints require a bit more work and take longer before you can move on from them while the glue dries. But each creates a good and strong joint for the projects we’ve used them for, from frames to tables to desks.
In preparing for this piece, we found a study on multiple joinery methods that measured the breaking point for each by applying pressure in attempts to separate or break the joints. We learned a lot about joint strength, too, as the testing included dowel joints, pocket hole joints, biscuit joints, and mortise and tenon joints.
Each of these forms of joinery use a jig in some capacity to create holes or openings; one of them introduces metal (the pocket hole screws), while the others employ a piece of wood to join workpieces (biscuits, tenons, and dowels). After the joints were created, pressure was applied to each to ascertain the breaking point.
As a control for these tests, the same woods were used in each instance. One final measure of control included the use of glue in the pocket hole joints, since glue is used with the other three.
The results were telling.
The dowel joint required 153 lbs of pressure to reach breaking point; the pocket hole joint required only 99 lbs of pressure.
We were surprised, as we’ve assumed pocket hole joints were stronger. The test results were even more impressive with the mortise and tenon joints, where between 202 and 226 lbs of pressure was required to reach breaking point, the range having to do with the type of glue used (yellow glue, titebond, and epoxy). The numbers speak for themselves, and no further comment is needed.
The traditionalists, those who adhere to the old ways that did not include metals being used in joinery, are no doubt pleased with these test results. They will suggest it cheapens a project to use screws, nails, brads, or any other metal in joining two pieces of wood.
Modernists, and especially Kreg, will argue that numbers be damned, the pocket hole joint is the stronger and more long-lasting choice.
We think the Kreg jig is a cool tool, and love its ease of use. We also like the purist approach to joining wood, and do take some pride in the “no metals” approach to joinery. After all, woodworking is a process – feeling the wood, “seeing” what is meant to be, respecting the joinery ways of the past, having the patience to work with it through to completion.
Numbers are numbers, though, and the testing seems to have been open-minded and fair, apples to apples.
We’ll straddle both sides of the debate, though. Pocket holes and dowels can co-exist in our shop, and we have no doubt we’ll continue to use both methods.