Making 'Pocket Dowel' Joints

A "pocket dowel" joint combines the strength of a dowel joint with the simplicity of a pocket screw joint. Nick shows how to make these unique joints quickly and easily using an ordinary pocket screw jig and a 12"-long aircraft drill.

Song: Silver Dollar
Artist: Roy Edwin Williams

[WorkshopCompanion]

By the way, I made the pocket hole joint in 3/4" (19 mm) thick wood. To do that, I put the the drill stop collar 5" (127 mm) back from the tip on the drill, and positioned the pocket screw jig so the bit entered the wood about 1-1/2" (38 mm) back from the end of the board.. The dowels were 3" (76 mm) long. When assembled, there was about 1-1/2" (38 mm) of dowel on each side of the joint.

Additionally, I have had two illuminating questions in the comments, and I would like to share these with those of you who are interested. I can't pin more than one comment at a time, so I'll post them below.

The first is from a viewer who asked why wooden dowels would be stronger than metal screws. Great question. Here's my answer:

At first glance, it would seem the metal would be stronger than wood. But there are actually three materials in a pocket joint, not two -- the metal in the screw, the cellulose fibers in the wood, and the lignin, a glue-like polymer that holds the cellulose together. (Let's ignore the adhesive in this analysis for a moment.) By far, the weakest of these materials is the lignin.

If you look at a cross section of a pocket hole joint (one made in the end of a board), the head of the screw presses against the bottom of the pocket hole. There is about 1/2" (13 mm) of wood between the bottom of the hole and the end of the board. The cellulose fibers (wood grain) in this hole are parallel to the screw, so we are dependent on the lignin in this 1/2" long section of wood to keep the joint together.


The second viewer asked me why we needed dowels at all. If glue is stronger than wood (as many of you who have seen Patrick Sullivan's experiments now believe), could we just do without the dowels altogether? My two-cents worth:

It's a misnomer to think of glue as stronger than wood. Modern adhesives are indeed stronger than one component of wood, but not wood itself.

For engineering purposes, it's useful to think of wood as a composite material. It consists of cellulose fibers bound together by a glue-like polymer called lignin. The cellulose is remarkably strong, the lignin is comparatively weak. Glue is stronger than lignin, but weaker than cellulose. When you break a glue joint, there are often pieces of splintered wood stuck to one part or the other. If you examine these pieces, they will seem to have split off the other board rather than have broken. The lignin fails before the glue does, and the wood splits parallel to the cellulose fibers. The fibers themselves remain largely intact.

Additionally, these fibers are extremely long, 100 times longer than they are wide -- this is what gives wood it's grain and makes it a great deal stronger along the grain than across it. This is why It's much easier to split wood than chop it. In the first instance, you simply break the lignin that holds the cellulose fibers together; in the second you're trying to cut through the fibers themselves.

This is the driving principle behind wood joinery. Dowel joints, domino joints, biscuit joints, mortise-and-tenon joints all send lengths of cellulose fibers across the joint seam, making the joint stronger than it would be if secured by glue alone. Secondarily, dowels, dominoes, biscuits, and tenons increase the gluing surface, adding more glue to the joint. This too increases the strength.

[ssuqfxp]

Never thought of using pliers to create the grooves in the dowels, another genius tip. Thank you Nick.

[frankcoit]

That is a rather attractive contrast in wood. Very good indeed.

[nickmastro]

If only I had this man as my high school instructor! Thank you for sharing.

[DeadlyEnzyme]

It’s like one of those local tv shows from the 90s where it’s just some guy being helpful and infinitely knowledgeable. I fucking love it

[NathanNostaw]

I never thought of using the pocket jig like this. Thanks for the great idea. I also like the dowel grooves with vice grips tip. So simple.
Cheers

[calvinchevalier]

As a mechanic I have no idea what he’s talking about but I’ll always stop to appreciate another tradesman sharing and being proud of their craft, hell of a job👍

[CasmsVR]

I'm not a carpenter or a wood worker.
Me: I'll definitely save this in my private playlist just in case.

[robertfergusson]

As someone with 6000 hours as a wood machinist that used to make a lot of various jigs, that combo never occured to me. Neat.

[abundantabsurdity]

I really like this guy. He seems like the Bob Ross of wood working.

[zochi_]

Dude, you aren’t just a woodworker. You look like the physical manifestation of a woodworker

[andrewluv]

I'm glad we still have people in the world like you sir, 🙂.

[wearthedead]

I miss my dad. And I’d pay you just to hang out for a couple hours. Thank you for your content.

[angryginger]

I've seen more great ideas from this guy in a week than from a dozen other woodworking channels in the past year.

[anthonyclaypool]

Nick is literally the best. A national treasure. Total pragmatism with no fru-fru, but cranking out awesome and beautiful stuff. I'd pay good money to see him and Paul Sellers do a build off!

[petergambino]

Not only is this man talented and smart, he is an excellent communicator, and teacher. What a great man he is.

[rockingbalboa]

The ease that "wood shop grandad" can explain these things so quickly and simply *chefs kiss*

[RAGordy]

Why is this craftsman blowing my mind this morning! In all my years of woodworking, why have I never thought of this?

[brianmerritt]

Thank God for YouTube. Guys like this who deserve TV shows can simply make their own show.

[robschaffer]

Fantastic idea! And the contrasting wood looks interesting, too!