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I have been referring to this site for quite awhile, and am finally undertaking my first “fine furniture” project. My question is whether there are some general rules for the proportions of a mortise and tenon joint. My project requires a tenon on each end of a board 5.5″ wide x 1.25″ thick x 44″ long (excluding the tenon length) into the 1.75″ side of board that is 3.5″ wide. I plan to peg the tenons, instead of gluing them, so that I can break the piece down if/when it needs to be moved.
My plan was to have a 1/2″ shoulder around three sides of the tenon, and no shoulder on the rear face, which won’t be visible.
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Stefan,
The basic rule of thumb for a stub tenon is 1/3 the thickness of the stock, it's cheek slightly less than 2/3 the width of the stock, and it's length about 3/4 the width of the of the stile (or leg). It should be 1/16th shorter than the depth of the mortise. An offset tenon is usually used where the rail lines up with the face of the leg or stile.
Loose tenons are usually keyed not pegged. There is also a loose stub tenon used on a stretcher that goes into a leg using a bolt that goes through the leg into the end of the stub and the stretcher has a mortise for the square nut to secure the assembly.
A brief description of your project would go a long way in advising you on the best approach to take.
I also highly recommend Ernest Joyce's
i The Encyclopedia of Furniture Making
, I understand that it is still in print.
Dano
*Dano, Thanks for your helpful reply. Sorry for not providing the backround on the project. I'm making a French country armoire, in the vein of what Chris Gochnour details in FWW #142 and in another article about "knockdown furniture". However, this piece will be in the corner of a room, therefore I'm only making the front frame and doors, and will make a set of shelves of birch plywood which will be hidden in the corner behind the armoire "front". One rail will be at the top of the stiles (with a crown molding on top) and the other rail will be 6 inches from the bottom (i.e. the distance between the bottom of the rail and the floor). The fronts of rails will indeed be flush with the front faces of the stiles. Because the mortises will be quite large, I thought it would be prudent to have the mortise inset the 1/2" from the front of the stile to avoid "blowing out" that front cheek of the mortise. Likewise, because the top edge of the top rail will be aligned with the top of the stile, I thought that the 3/4" shoulder on the top of the rail would allow for enough end-grain material to prevent weakening those mortises.Please forgive me if I'm not explaining this well, or for improper terminology. I plan to order Joyce's book soon, thanks for the recommendation.Stefan
*Stefan,No need to apologize. The issue that you mention also has a pretty good article by Gary Rogowski, "Tenoning Strategies".By the dimensions you gave in your original post, the tenon for the rail would be 27/32" in thickness offset to the back 13/32". I recommend that the bottom shoulder be at least 1/4" and the top at least 1/2", that gives you a tenon width of 4 3/4" and it's length at least 2 1/4" where the mortise is 2 11/32" deep, which is a pretty substantial tenon. I would like to ask why the stile 1/2" thicker than the rail?My main concern is; there does not appear to be a way to draw the joint together tightly and keep it tight. I don't believe a pegged tenon is the answer. I have not seen a French Country Style piece with a keyed loose tenon but, perhaps you could make it work. The key would be wedged shape, going into a mortise at the end of the tenon. This would draw the joint together. For this application you would need two, IMO. Hope this helps.Dano
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