Mortises and tenons that meet in a corner

[Greg Guarino]

The drawing shows a through tenon and a blind tenon that meet (or nearly so) inside a leg.

Questions:

How deep is deep enough to make a mortise and tenon joint useful?

Are there other strategies to deal with this situation?

Would you make a blind tenon that was smaller in the vertical dimension, allowing it to go deeper, through the other tenon?

Would you bother making the blind mortise and tenon joint at all, or might you choose some other kind of joint, since it won't show?

[Leon]

If you have the room that is a possibility

If you move the aprons out closer to the outside of the legs the tenons will go in farther before they meet. I have done this and 45'ed the ends of the tenons where they meet. Keep in mind that tenons don't have to be centered, they could be nearer the front of the aprons.

[Swingman]

There are indeed traditional proportions for M&T joinery that have stood the test of time, from which you can depart somewhat, to wit:

~ The depth of a stopped mortise should be approximately 3/4 the width of the leg or stile.

~ The thickness of a tenon is approximately 1/3rd the thickness of the rail, or the width of the chisel used to cut the mortise that comes closest to that.

~ A tenon usually runs the entire width of the rail or, when the rail is unusually wide, a pair of tenons are used (AKA, double mortise and tenon).

Quite easy, an acceptable, to miter the tenons that meet

[John McCoy]

Greg Guarino wrote in news:mehli2$osm$ [e-mail]:

Generally you want a longer tenon in preference to a shorter one, but it's usually determined by whatever you're putting the mortise into.

For a smallish piece like your's, I'd think a 1/2 inch tenon would be fine.

Well, normally both tenons are blind and meet inside the leg - both being cut @ 45 degrees on the end like a miter.

No - if I was doing a thru tenon for aesthetic reasons, I'd just butt the blind tenon to it, as you show.

Yes. Mortise and tenon is easy and strong, it's the best way to attach the rail to the leg. If I was worried about the strength of the short tenon, I might add a triangular brace/glue block on the inside (joining the two rails - it'd have to be notched to clear the corner of the leg).

John

[Sonny]

Triangle glue blocks in the inside corners: On some upholstered pieces, I' ve seen the addition of a screw through the center of the triangle block, i nto the corner of the leg. I'll sometimes use this addition of a screw, w hen repairing a damaged/compromised corner, especially one that has powder post beetle damage.

Additionally, beyond the subject of this thread: More recently, when repai ring powder post beetle damaged corners, and thanks to others, here, I've l earned epoxy works great, to rebuild a compromised corner, i.e., a corner w eakened/pockmarked with PPB holes. This time of year, here, the larvae, in infected pieces, are becoming active. I just finished an antique caned so fa and two chairs set, that had old damage and present larvae activity. Ot herwise, these corners had dowels, not mortise & tenons.

Sonny