Large mortise and tenon joint

[Anthony Scott]

216407
The plans for this project call for 8/4 lumber to make the base. Since I already have the 4/4 lumber for this project I was thinking of gluing up the legs and stretchers using four pieces of 4/4 lumber. For the end stretchers that require a tenon, I will cut the two on the outsides shorter than the two on the insides to form a tenon.
For the inside part of the legs that require a mortise I was going to do the opposite... but how would I deal with the top part of the mortise? Perhaps make a block that fits in to the mortise above the tenon?
Looking for suggestions.
Thanks

[Jerome Hanby]

I think that's exactly what you do!

[Paul Symchych]

I made my bed's head and footboards just that way.

".. but how would I deal with the top part of the mortise? Perhaps make a block that fits in to the mortise above the tenon?"

You shouldn't need the small block above the top mortise. Make the tenon with no top shoulder [flush with the top of the leg] but with a larger lower shoulder, then pin it with a wooden dowel. Do that at both ends of the stretcher and there will be no racking.

[Anthony Scott]

I was worried if making the mortise with no top part would make the joint too weak for a workbench.


I made my bed's head and footboards just that way.

".. but how would I deal with the top part of the mortise? Perhaps make a block that fits in to the mortise above the tenon?"

You shouldn't need the small block above the top mortise. Make the tenon with no top shoulder [flush with the top of the leg] but with a larger lower shoulder, then pin it with a wooden dowel. Do that at both ends of the stretcher and there will be no racking.

[Paul Symchych]

A quick and easy answer: If you want to test this make a pair of legs and stretcher out of 3 pieces of 4/4 scrap wood. A foot or two long for each of them. Once glued and pegged try to get it to rack. Unless you fracture the peg at both ends it will be stable. An oversized -double size or more- lower shoulder will keep it from racking.

[Philip Rodriquez]

If this is for a work bench, I would use a bridle (al) joint for the top of the legs. You would never have to worry about the joint blowing out on you if you lifted your bench to move it around.

[Carl Beckett]

If a workbench - depending on what level of construction style you are after - you could basically 'frame it like a window'. That is, instead of cutting the mortise/tenon - simply have three pieces of wood - first under the the bottom of the stretcher - the second between the two stretchers - and the top caps it off. Nail into the blocks at the end of each stretcher (or toenail - or go into the stretcher all the way through the outside pieces). The stretchers get sandwiched between it all.

Crude. But will be pretty strong. (have made workbenches this way and they hold up well). Again, might not be what you are after if you like the traditional joinery. For traditional, I like the bridle suggestion.