What would you call this joint???

[Dale Schafer]

I'm thinking to try this joint and was wanting to see if I could find any information on how to do it and what sort of tolerances should be allow for wood movement. To do that I need to know what to call it.
Any help appreciated.

Half-Shouldered, Through-Wedged Half-Dovetail?

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[Peter Aeschliman]

Very interesting.

I'd call that a "wedged through tenon." Or maybe a "knock-down wedged through tenon" (to articulate the fact that it can be disassembled). But I'm not sure what I'd call that angled/half-lapped section, and I'm definitely not sure what that overlapping piece does for structural integrity.

It looks cool, but I'm not sure about that wedge... I'm partial to this kind of wedge myself: http://www.wkfinetools.com/contrib/mSinger/throughTenon/througTenon-2.asp

Vertical wedges are perpendicular to the wracking stress that they resist and they pull the joint tight laterally... whereas this wedge is parallel to the wracking stress. So my gut tells me that this joint will come loose and require the wedge to be driven back in over and over. But I'm open to counter-arguments. :)

[Larry Edgerton]

I kind of agree with Peter on that last part, but the tenon and mortise are wedged on the bottom so all the wedge has to do is keep the tenon from rising. the slope of the tenon will use gravity to pull itself tighter. Lateral motion would be taken care of by the wedge on the bottom. I'll have to build one to play with but I question its design as well.

[Dale Schafer]

I have no experience with any wedged tenons. Here is some info regarding a similar joint on a bench without the inset shoulder:


It is referanced below and shows a cut-away view, minus the wedge.
http://www.popularwoodworking.com/wo...nch-leg-joints (http://www.popularwoodworking.com/woodworking-blogs/editors-blog/21st-century-workbench-leg-joints)




For joinery to last, you need to be careful about how much material is removed. If you cut away most of a big honking leg to make a joint, you lose the structural value of the leg and may as well have used a skinnier one.http://www.popularwoodworking.com/wp-content/uploads/bot_1647-300x200.jpg (http://www.popularwoodworking.com/wp-content/uploads/bot_1647.jpg)At right is the bottom rail joint as I was working on it. All of the joinery was cut before the legs were laminated. To put this one together in the finished bench, the rail is lifted so the end of the rail passes through the narrow end of the socket. That narrow end is about 1/4″ wider than the rail to make this easy. When the end of the rail is through the other end, it drops down to engage the joint and a wedge is tapped in from the outside.
http://www.popularwoodworking.com/wp-content/uploads/Joints1447-212x300.jpg (http://www.popularwoodworking.com/wp-content/uploads/Joints1447.jpg)From the end you can see the wedge in place and how little of the leg is missing. In the event that something loosens up, a few taps on the wedges take care of it. The bench doesn’t loosen in use however, and that is the really cool thing about these joints. Most of the stress on a bench in use is in the long direction as in planing. When you push on a dovetail, the joint wedges tighter together and any wobbling stops.
If these were tenons and mortises, any force exerted in that direction tends to pull the joints apart. Yes you can drawbore the joints or bolt them together but there isn’t any wood in the joint itself to resist that force. Over time things start to wear and eventually you have a wobbly bench. The things you can do to a mortise and tenon to resist that might work, but the tradeoff is making the bench more difficult (or impossible) to take apart if you ever have to move the thing down to the basement or up the stairs.












http://learningwoodworking.wikispaces.com/file/view/wedged_half_dovetail.JPG/191267740/576x345/wedged_half_dovetail.JPG