Intersecting tenons?

[Jack Porter]

I'm planning out an entry bench/storage unit at the request of the wifey. I plan on using M&T jionts, however, at the front legs (leg size=1.5"x1.5") where the rails meet, the tenons would intersect if longer than approx 1/2" (into the leg). Thoughts?:confused: I guess I really never ran into this situation before. Any advice is appreciated.

A sketch is attached to help clarify the situation.

[Jamie Buxton]

One common approach is to offset the tenon toward the outside of the leg. That is, don't expect the tenon to be centered on the rail. Push it toward the outside face of the rail.

If you really want to inset the face of the rail from the face of the leg, like your drawing, you can even offset the tenon all the way to the face of the rail. That is, the only shoulder on the rail will be on the inside face.

With this approach, you should be able to get a tenon which is an inch long in a 1.5" square leg.

Another approach is to reinforce the corner with a block which runs from rail to rail, just inobard of the leg. That is, it would be three or four inches long, with 45 degree miters on the ends. It is typically screwed into the rails -- no fancy joinery.

[Joe Scharle]

Not uncommon, add 1/4" and miter. Don't be concerned if the miters aren't picture frame neat. I would also make the tenon as 'fat' as possible to support weight on the seat. The cheeks on the tenon are for good looks anyway.

[Jack Porter]

Not uncommon, add 1/4" and miter. Don't be concerned if the miters aren't picture frame neat. I would also make the tenon as 'fat' as possible to support weight on the seat. The cheeks on the tenon are for good looks anyway.

Add 1/4" to...? thanks
I was planning on 3/8" tenons, I don't think I would want to go much fatter with 3/4" rails

[Greg Hines, MD]

You should cut the mortises first. If you center them from both the front and the side, and they are long enough to support the seat, you will have intersecting mortises. If you then cut a miter at the end of your tenons, they will meet inside the leg, and give you a great deal of surface area for glue, and will be as strong as you can make them.

The alternative is to offset one set of mortises, say, the end mortises, to the inside of the leg, while you then offset the mortises on the front and back to the outside of the leg.

Either way will work, though the first way is usually easier to do, because you only have one mortising and tenoning set up needed.

Doc

[Chip Lindley]

I 2nd what Dr. Hines says. Intersect the tenons and miter the ends. Your mortise and tenon cutting setup will remain the same for all four legs, and the hidden mitered tenon ends will become solid when glued together.

[Jack Porter]

You should cut the mortises first. If you center them from both the front and the side, and they are long enough to support the seat, you will have intersecting mortises. If you then cut a miter at the end of your tenons, they will meet inside the leg, and give you a great deal of surface area for glue, and will be as strong as you can make them.

The alternative is to offset one set of mortises, say, the end mortises, to the inside of the leg, while you then offset the mortises on the front and back to the outside of the leg.

Either way will work, though the first way is usually easier to do, because you only have one mortising and tenoning set up needed.

Doc

thanks Greg, I think this is just what I'm looking for:cool:

[Frank Drew]

Add 1/4" to...? thanks
I was planning on 3/8" tenons, I don't think I would want to go much fatter with 3/4" rails

Jack, I think Joe meant that you could add 1/4" to the length of the tenons, not to their thickness. And for 3/4" rails, 1/4" or 5/16" tenons would be perfectly adequate.

If you make a plan view (i.e., from above) of your rails and legs, you can see how offsetting the tenons to the front of the rails, as Jamie suggests, will allow longer tenons; as long as there's at least a minimal shoulder at the front (even 1/16" would do), the joint will have the integrity you need.

Apart from mitering the tenon ends, which is what I usually did, another method to allow longish tenons in this situation, would be to haunch the tenons, with opposing haunches on the meeting tenons (up on one, down on the other).

[glenn bradley]

My latest project used mitered tenons for just this reason.

[Joe Scharle]

Add 1/4" to...? thanks
I was planning on 3/8" tenons, I don't think I would want to go much fatter with 3/4" rails

Apologize for the brevity; but Frank answered for me. 3/8" tenons are plenty and twice the strenght of 1/4", leaving 3/16" cheeks all around. One more point is when you have intersecting mortises, there is a chance of blowout at that point on the stile unless the tenon fills the void. Don't be overly concerned, just go for a good fit.

[Frank Drew]

Just as a point of no doubt unnecessary clarification: You can only cheat on the tenon cheeks (offset the tenon to the outer part of the rail) if the rails are set back from the faces of the legs, as in the OP's drawing; otherwise, the mortise cheeks will be way too thin.

[Bob Wingard]

If you REALLY want to add invisible strength, dovetail the intersecting ends.