Replies

1. 
   Bob_Van_Dyke | Sep 30, 2007 03:37am | #1

   Sizing tenons depends on a few factors and there are not too many "rules". Basically it is a balancing act- You want to have a large tenon but realize that the larger the tenon is, the more wood you will need to remove in the mortise in order to accommodate it (which means that you could be weakening the piece with the mortise)- so- rule of thumb to get you started: the thickness of the tenon starts at 1/3 the thickness of the piece- so- on a 3/4" thick table apron you would do a 1/4" thick tenon-BUT- 5/16 or 3/8 would also be appropriate!- in many cases it boils down to the size tooling you have available- If I have a 3/8" bit only- then that is what I will use- I would not go out and buy a new bit if I had something close that will work.
   The length of it? It depends on how thick the piece is that contains the mortise (and if there are two mortises in that piece- do they meet inside? Picture a table leg with two aprons coming into it at right angles- if they meet inside the leg then that will determine the maximum length)
   In the table apron you describe I would probably make the tenon between 3/4" and 1" long
   How wide should it be? once again- as wide as possible (to get the max glue surface) without taking away strength in the leg that contains the mortise. (and without being so wide that cross grain wood movement becomes an issue!)
   So- your example of a 3 1/2" wide leg? I would start the tenon 1/2 to 3/4" down from the top of the leg (without getting into "haunched mortises-a whole other level of mortise and tenon...)
   and I would usually stop it about 1/4" from the lower edge of the apron (I like to have a shoulder all around the tenon -it covers up any inaccuracies in your mortise)
   so- the mortise would be 2 1/2 or 2 3/4" wide

   As far as when to use two tenons? Only on something very thick that needs to be Very strong- like maybe on a workbench or very large and heavy table

   As far as rules on the inset or relief?? You can check with the fashion police- I am sure they have some rules- but it is really up to you and what looks good. The Shaker Hall table we do in my school has a relief (or reveal) in the apron to leg and I studiously avoid measuring it so that students will have to tell me what reveal looks good!

   Hope that is all a help. Let me know if you have any more questions
   Bob Van Dyke

1. 
   MrChipper | Oct 10, 2007 12:07am | #2

   Bob,

   Sorry I am so tardy in replying - had house guests so haven't been in 'shop' mode.

   Thank you and yes it does help.  I did a bit of overkill I suspect.  For the 3-1/2 in. apron I made tenon 2-1/2 x 1/2 x 1-1/8 inches.  Did dry fit yesterday and all went together well.  also put braces across corners using hanger bolts screwed into legs.  Cut 45 deg. 'mortise' in aprons and they also fit well.

   Table is for large - 46 in. x 21 in. - doll house(from kit) 35 years ago.  This table will have a raised edge and carpet casters so it can be pushed around by granddaughter and friends.

   Thanks again,

   John