Mortise and tenon joints are usually referred to as wedged through (142:1) and stub or blind (142:2). The former is more applicable to joiners' work where the end grain of the tenon shows on the edge of the stile and is painted over, but as it has decorative possibilities it is included. The familiar type for furniture is the stub tenon with or without haunching (142:3) whose function it is to keep the unsupported part of the rail from twisting on the face.
All tenoned work follows the same general principles. The width of the mortises is slightly over one-third the thickness of the stile (142:5) but pitched according to the width of the hand-or power-chisel available. The rail width in corner mortising is also divided into three, one-third for the haunch or seating and two-thirds for the tenon, less a bare 1/16 in (1.5 mm) shoulder at the bottom edge to cover any slight gap caused by a slack tenon or bruising of the mortise socket end in levering out the waste in hand-methods. The final width of the tenon itself less the haunch becomes the length of the mortise cut to receive it. In all framed-up work it is always better to provide an extra length to the stiles to form a horn (142:1) at top and bottom which helps to prevent the splitting of soft wood while deeply mortising, and also to protect the corners from incidental damage. These horns are left on until the door is fitted.
Where the stiles and rails are grooved or rebated/rabbeted for panels the mortises are pitched to coincide with their position; they can be wider but not narrower than any groove or rebate in the rail. The mortise depth should be slightly more than the length of the tenon so that a small gap is left for surplus glue, while plenty of wood substance should be left between the bottom of the mortise and the outer edge of the stile, certainly not less than3/16 in (5 mm) even for a small door.
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