Mortise & Tenon Leg to Skirt (Rail)

[Bob Grier]

Mortises have been cut in the legs for this storage bench. I planned to miter the the tenons where they meet inside the leg mortises. Second thinking (guessing) about whether I should include a short tenon extension between the 2 primary tenons to either provide more shear strength to the tenon or to maybe help prevent splitting of the skirt between the tenons due to humidity shrinkage of the skirt, or to give more glue area, or .... has sent me here to ask for your thoughts. I am not particularly excited about cutting more mortises but will do if there is a reasonable chance I should do so to prevent a failure.

In researching this question on this site, I ran into another design item. Now I have 2 design thoughts spinning out of control in my head. This latest thought is whether the 45 miter where the tenons meet inside the leg is a good idea. In my research, someone suggested that overlapping the tenons is better than using a miter. I am starting to think that too. It would be more work but it seems to me to be a better design. I like to minimize work so I am here asking for your thoughts. I want to do what is most prudent thing to do, not necessarily the most conservative.

If your experience shows that the 2 tenons as designed will work just fine, I would like to continue as originally designed. If your experience shows that I may have a problem, then I will make a change. I just don't have real experience to base a decision on.

Thank you for your help.

bench mortise & tenon.jpg

[Jamie Buxton]

Going into a leg that's 2 1/4" square cross-section, there's plenty of room for tenons. I'd make them about 3/4" long; that's plenty of glue area. I might displace the tenons toward the outside of the leg, rather than putting them in the middle of the skirt. With that approach, there should still be meat in the leg between the mortises. But if already have cut the deep mortises, you're committed. Keep going.

[Malcolm McLeod]

Since you have cut the mortises, I'd also press on as-is. You don't mention the skirt material, but if you simply make the lower tenon's height ~1/8 less (than 2-1/4), it would allow for some stress-free seasonal movement in the skirt.

And if it was me, I'd shorten the narrow skirt's tenon length (leave the long skirt's tenon at 1-9/16 L). It's easier than a mitered end and the narrow dimension of the bench is subject to less racking force.

[Bill Adamsen]

I like what Malcolm has suggested on the lower tenon. Even with an inch long tenon (assuming the tenon itself is 5/8" +/-?) there'll likely be no need to miter.

[Bob Grier]

The skirts are 7/8" cherry and the legs are cherry. I will leave some space at top of bottom tenon. The bottom of the storage area will be 3/8" plywood. There are 2 compartments divided by a 7/8" cherry divider. The plywood bottom will be glued into a 3/8" mortise around the inside circumference of each compartment. Sort of a diaphragm type construction. The top will be 2 hinged lids of 3/4" cherry with 2 thin inset accent cushions.