Replies

1. 
   SgianDubh | Jul 26, 2006 09:39pm | #1

   It's likely that the rail has a forked tenon with one mortice slightly extended. It's probable that only one fork of the forked tenon is glued leaving the other to float in the matching extended mortise. See the click on for the general idea. Slainte.

   Richard Jones Furniture

2. 
   SgianDubh | Jul 27, 2006 11:59pm | #2

   Thinking about it wooddod, I really only gave you a half answer. I described a forked tenon and how it's used on a wide rail and only partly glued.

   But I didn't really offer a guideline for the maximum width of an M&T that's glued the length of the mortice.

   125 mm (5") is about as wide a tenon as I really like to go and do a full glue up. Certainly at about 150 mm (6") wide and it's borderline as to whether or not I fork the tenon. The form of the fork may be a wide glued tenon and a narrow unglued tenon on one dge or the other.

   at 175 mm (7") wide I'll definitely create a forked tenon. The tenons may be equal in width, or one may be wide with a second much narrower-- it depends on the job.

   In part the reason for forking the tenon is to allow the movement required in the width of the tenoned part. Secondly creating a fork in the tenoned member means creating a pair of mortises in the length of the wood. The plug of wood between the mortises can help the mortised members strength characteristics-- the plug assists in keeping the mortise cheeks tight against the tenon faces in service.

   A long deep mortise  will sometimes show the wood on the outside faces of the morticed part bulging away from the tenon cheeks due to things like wood movement during moisture cycling and less than well matched grain patterns chosen during the parts selection and orientation. Slainte.

   PS. I'm also surprised no-one else has jumped in here with information-- but there ya go. 

   Richard Jones Furniture

   
   

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   Edited 7/27/2006 5:07 pm by SgianDubh

1. 
   joinerswork | Jul 30, 2006 05:59pm | #3

   Richard,

   No need for anyone to jump in.  You covered the topic well.

   Ray