I normally use a standard mortise and tenon joint and usually use 1/8 ” haunch on the top and bottom of my joints.
I am making chairs for the first time and decided to use straight loose tenons for the side rails between the front legs and rear legs because the joint is at an 85.5 degree angle (i.e the front legs are wider than the rear necessitating the angle tenon). (See FWW # 190 pages 51 to 53). The problem – I designed and cut the angled mortises on the legs using my standard 1/8″ haunches and am starting on the mortises for the side rails, it dawns on me that the loose tenon will only be captured by 1/8″ of wood at the top and bottom of the side rail. I doubt sufficient to support a leg very well. My recovery plan is to cut standard mortise and tenon but angled.
My question – might he joint be ok as is?
Thanks for your thoughts
Dan
Replies
Dan,
In making repairs of chair seat rails with broken tenons, I frequently install replacement tenons by slotting the end of the rail where the tenon was broken off, and slipping in a replacement "loose" tenon. Haven't had one come back yet.
What you are describing is similar to a bridle joint, the integrity of which depends on the fit of the joint and the strength of the glue bond. The 1/8" of wood at the end of the rail/ the loose tenon won't add any strength, but if the cheeks of the tenon fit properly within the walls of the mortise, that's where the strength of the joint is derived.
If the idea still doesn't sit well with you, you might consider cutting a shorter mortise into the rails, and making the loose tenons themselves with a step or haunch in them.
Ray
Thanks Ray. Later in the day the idea of a stepped loose tenon hit me and that is the way I am going. I understand your comment on the bridle joint - if cheeks properly fit and glued it should hold up but still scares me. Re-assuring that you do this in your repairs and works. I remember FWW articles looking at the strength of mortise and tenon, lap joints, and bridle joints and how they hold up under load and that bridle joints hold up as well as mortise and tenon - but my simple engineering brain just can't get the concept to sit well in my head.
Anyhow you confirmed my stepped tenon approach so I am good to go. Take care.
Dan
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