Mortise and Tenon Joint - Wedged Tenon

Mortise and Tenon Joint. In this video Rob Cosman shows you whoe to hand cut a wedged mortise and tenon joint. This joint is a variation on the standard mortise and tenon joint, but is a much stronger joint due to the wedging action.
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[RobCosmanWoodworking]

Want to learn more about the mortise and tenon joint? Check these videos out:

[dp]

This was a great tutorial. One tip for anyone trying this at home: before you cut the kerfs in the tenon to accept the wedges, drill a small hole (about 1/8" for a tenon the size of the one in the video) through the tenon near the shoulder where you want the kerf to end. This does a couple things for you. The round hole eliminates a stress point and reduces the likelihood of splitting. It also gives you a bigger target to saw towards. Happy woodworking, everyone!

[joschmoyo]

Lol. If you listen carefully you can hear the moment Rob broke one of the tenon kerfs because he cut it to close to the shoulder.
Kerfing tenons is risky, especially if it's a brittle timber with a short tenon.
Window/door joiners don't usually kerf the tenon itself because there can be a risk of splitting so you just drive a very rough sawn wedge in to edge to fasten it.
Not quite as strong but if the glue fails its easier to repair because you can drill out the old wedge and put in a new one.
Cabinet makers often drill a hole at the base of the tenon before cutting a kerf down to it so that the load of the driven wedge is spread and reduces the chance of splitting.
You don't need to spread the tenon nearly as much as Rob did.
3mm is plenty, 2mm is perfectly good enough. That way your kerf can be further in and thus stronger.
Many joiner do not bother to actually angle the mortise either.
It's more about compressing the tenon tight while gluing up and being able to crack the frame to get rid of any wind.
Wedged tenoning avoids the need for sash clamps. That's why we use them. It's fast.

[createlovehappy]

Love your channel. It’s fun to watch a master at work plus your teaching style is detailed and easy to follow. I’m retired now but used to do a lot of woodworking and finish carpentry. Now kicking the crap out of cancer and winning so I can stick around for my babies. Prayers and healing thoughts are welcome if you are so inclined. Thanks for all you do.

[Ace-igvs]

This guy is waaaay underrated. That's probably been said many times but I'll say it once more.

[Kunfucious]

I love the future. Between Cosman and Sellers, you could learn most of what you need to, at least, get a good start in woodworking. Nothing can comes close to hands on, but the details you learn here would take so much experience to figure out.

[trep]

Thanks for the lesson. I’m about to cut my first wedged tenon. My tools aren’t near your level but they do the job for me, I’ll do fine. However, I do have the same indispensable magnifier you have and I’m over 70 years old. This is a good video.

[Maxime-hoiv]

Oh god, finally someone cuts this in half and shows the non-sense of how people do this.
1) wedges are wedges, they should be thin
2) the outside of the mortise should not be that wider than the inside (if the gap is small, the wedge do not need to be that big, which avoids cracking the tenon)
3) the wedges shouldn't be that close to the sides of the tenon
4) if you make a tapered mortise, the angle of the flared sides of the mortise need to be gentle
5) if you make a tapered mortise, it should go only half way through the length of the tenon, so that you keep straight edges on part of the tenon/mortise
6) the cuts you make on your tenon (the holders of your wedges) should be 2/3 max of the length of your tenon, they should never extend to the shoulders
The idea is that your "new" tenon (which is your "old" tenon + the wedges) will be just slightly larger than your mortise, which is enough. And this is the important part here: the strength of the joint is that the tenon is slightly bigger, not that there is a tapered mortise.
It should be one of the strongest joint, not just aesthetic.
If done well, the tenon should never crack. You don't want what you can see at 5:46 where the left side of the tenon is actually splitted (you can also see it breaks at 57:31).

[TheRunereaper]

I've just spent an hour on the edge of my seat. This was like watching a man trying to climb the North face of the Eiger, from a safe distance. Every move fraught with danger, one slip and you're gone! These videos of yours are absolute gems. Thank you for sharing Rob.

[ndothan]

I gotta say, Jake is getting really good with the camera. There has been a steady improvement in his skills over the years.

[sanramondublin]

Thanks millions from California.
Those who realy want to learn this, get a flavor of your experience also.
Please continue.

[Itstheoutputs]

Rob (I can’t see it anyway but it looks to be about that) Cosman I love watching you work. I can tell without looking you’re a man who’s spent most of his life sweating the details because that’s what creates quality. You make me want to take full width shavings and never sand again. I hope to get there before the clock runs out (64 but look like 84). If you ever have a class for the disabled that never served in the military, I’m there. Then again you’d have to pay my way cuz disability won’t cover that. Oooops, forgive the rambling. Anyway, keep up the great work and we’ll talk again next time my mind wanders.

Best,
Jim

[myfinalheaven]

Thank you Rob. I'm glad I came across this video.

I see other wood working Youtubers do this variation, but don't actually explain it. Listening to you explain it makes more sense.

[crazy-eyewoodguy]

I have cut wedged tenons for years, I always cut straight down and occasionally ran into problems, frustration and heaving large chunks of wood at the speed of light. cutting the wedge cut at an angle was genius. So simple, but I never thought to do it that way. Face plant when I seen you do it and I thought am so stupid....Thanks for the tips and your time. Sometimes it's the simplest thing.

[danbeeson]

Love the grip tape on the clamp handles! Everyone should do this for the sake of preserving the tendons on your hands and arms.

[taylor-]

Thank you for all these teaching videos! Your videos has taken my woodworking skills to a hole new level!

[ericsimpson]

This is such a comprehensive way of teaching. I always learn alot through each of your videos. Thank you for sharing your knowledge and talent

[torquilh]

When the cut was made at an angle, it goes really close to the edge of the tenon. It seems that this is a weak spot? Doing it this way means that you are only holding the tenon in with a few strands of wood. In the cross section that is shown, it actually looks like it is cut so close that it is not connected on one side. Would it be stronger to just bring those cits in a few mm, so it was not as close to the edge when the cut reaches the shoulder?

[P]

"If I knew anything about math, I could use this calculation to figure that out, but I don't so I'm just going to guess at it." Single funniest thing Rob has ever said. Lol. Much love man.

[johncoops]

At 57:33 he snaps one side of the tenon wedge off. That significantly decreases the strength.
I reckon he cuts them far too narrow at the bottom, and having the wedge run all the way down puts a massive amount of pressure at that point which literally snaps off the fibers where they are most vulnerable.
I've always cut the wedges short and rounded them off, so that the flexible part of the tenon can "curve into" the final position along the sides.