Wedged Thru Tenon Question

[fptahoe]

I am going to make couple of end tables for my daughter, and I want to have the legs come up through the table top as a thru tenon, and then wedge the tenon in from the top.  I have never done this before and I am thinking I need to chisel the mortise a little wider than the legs, on the two sides that are parallel with the wedges.  My question is how much larger should the mortise on those sides be?  If I use a 1/4" wedge, should the hole be chiseled the width of the leg plus 1/8" on both sides?  Smaller? Larger?  Thanks as always for any advice.  FPT

[fptahoe]

Forgot one other question: on the sides that I chisel wider, should they be angled on the same plane as the wedge, or am I just chiseling straight down?

[gjohn]

I would have two wedges per tenon, one on each side. Maybe 1/4" in from each side. The mortise should be angled on each side. The wedges would be 1/8" or so at the end of the tenon.

[bandit571]

Something like this?
 

   
when I was building a rocking chair 

   
Used one saw kerf on mine..

   
Underside of the arm rest....

   
Not too bad? Walnut  wedge, Pine rocker..
 

   

[barryvabeach]

FTP,  chop the mortises so all 4 walls are exactly straight.  Then widen the top of the two opposing walls very slightly.  I have never measured, but probably a 1/16 to 1/8 would be plenty.  When you cut the kerf for the wedge or wedges, remember that the wedges will fill that kerf, and only need to enlarge the top of the tenon a fraction to keep it in place.  If the top of the tenon, with the wedge, is 1/64 of an inch ( just to pick a small number at random) wider than the middle and bottom of the mortise, that tenon isn't going anywhere.

[EricU]

I made a short stool with wedged thru tenons.  I think the tenons were too sloppy in the mortises.  Now I have to fix one of the legs, the tenon broke.

[Bibliophile 13]

What you describe will work just fine. As said above, the mortise walls need not be widened much, no more than about 1/16”, I’d say.

[Handplanesandmore]

What Barryvabeach says...

Plus:

1 - orient your wedges probably (across grain) so they don't split your top;

2 - drill relief holes to prevent splitting the tenons

3 - the wedges must be long enough for the pounding and trimming

4 - the tenons should be proud of the top so you can plane or sand them flush.

Simon