coffee table design - robust enough?

[custard]

On this project it makes little practical difference, incidentally that's why I recommend a 12mm plus shoulder at the bottom of the tenon, it's to give you some wiggle room for exactly this issue.

If the splay angle is greater (common with chairs for example) then you get into the problem of short grain weakening the tenon, the normal solution to that is a mortice that's plumb to the mating faces on both sides of the joint allied to a loose tenon.

 

[nabs]

thanks - I am probably being thick, but why does the 12mm shoulder at the bottom of the tenon help?

 

[custard]

thanks - I am probably being thick, but why does the 12mm shoulder at the bottom of the tenon help?

One way this can go wrong is if the mortice (or even a dubbed over lip of the mortice) is peaking out from below the apron rail, with angled joinery it's quite easy for that to happen. You might decide to make the bottom edge of the apron co-planar with the top which will trim off a few mill from the inside edge of the apron rail. Or if there's a curve on the bottom edge of the apron rail, in real life that curve can creep back a whisker, which might then expose the mortice. On a rectilinear design you'd normally have a shoulder that's about 6mm, on an angled design make it 12mm and you're bomb proof.

 

[nabs]

ah - I see! thanks for the explanation