I'm helping my friend Lori with her maple dining table project. It's a trestle design, with a single stretcher, through-tenoned into the trestle legs. It's intended to be a knock-down design with tusk wedges holding the tenons. The stock was only 4/4, so the finished stretcher is only about 7/8" thick, which means the mortise and tusk would only be a little over 1/4" thick if the joinery is done vertically. That would probably work ok with a tough wood, but I feel like there's a small risk of racking forces splitting the leg with that narrow pressure point, and the proportions just aren't right in the context of the piece. The easy solution is to put the tusk tenon through sideways, but then it's just pinned and you lose the beautiful gravity-assisted wedge action that keeps the joint tight as the wood moves with the seasons.
So I came up with this. It's got a cross piece horizontally through the end of the through tenon. That cross piece is relieved in the back so that wedges can be put in to pull the joint tight. I did a quick prototype last night and Lori likes it. I think the madrone cross bar with walnut wedges looks nice. If it turns out ugly or fiddly, I can always just cut a single horizontal pin and do it that way.
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| Through Tenon, Pinned and Wedged - this is just a mockup using some blocks |
Update: This turned out great. The maple and madrone came out remarkably close in tone after a coat of Watco "natural" so I lost the coloring, but the physical aspects of the joint are solid. I did the joint the same way for the bench that goes with the table. The only trick I have to share is in fitting the wedges. I cut them really long (~16") with a tapering jig at the table saw. Then I tapped them into place, with all the rest of the parts cut, and marked where to cut them to length. That way I don't have to worry if one side is a bit tighter than the other.
