Manual of Purpose-Made Woodworking Joinery

Frame joints 23

infringements of the rule are usually disregarded.
However, you do have a choice; if a basic, single
tenon is not deep enough to be divided into two, after
haunch allowances, yet it fails the width- of- tenon
rule, then the actual tenon can be made five times
the tenon’s thickness, with the surplus width either
reduced equally to produce a haunch on each outer
edge, as indicated in Figure 3.7(b) above, to suit a
mid- stile intermediate rail; or – in the case of a top-
rail tenon – as well as the required reduction for the
top haunch, there could also be a haunched reduction
on the underside of the tenon to bring the tenon in
line with the five- times thickness rule. In either case, it
would produce a similar- looking double- haunched
tenon to that shown in Figure 3.7(b).

Haunches on traditional sashes

Figures 3.8(a)(b): On traditional, ovolo- moulded and
rebated sash material, because a normal haunching

groove cut in the relatively small- sectioned sash stile

tends to weaken the joint, a haunching spur is formed

from the stile’s long- grain, and the end- grain of the

rail’s tenon is cut back into the stock to form a so-

called franked haunch, as illustrated in Figures 3.8(a)

and (b) below. A detailed and illustrated explanation

of the scribing technique involved in making these

joints is covered in Chapter 4.

(b)

Figure 3.7 (b) Literal interpretation of the width- of-
tenon rule.

Haunching spur

Mortise

Stile Top Stile

rail

Top

rail

Franked haunch

Ovolo-scribe

Tenon

(a)

Figure 3.8 (a) A

franked haunch and

haunching spur to top

joint of sash.

Haunching spur

Mortise

Stile

Bottomrail

Franked haunch

Ovolo-scribe

Ovolo-mould removed

Stile

Bottom

rail

(b)

Figure 3.8 (b) Details

of scribed joint at the

bottom of the sash.