Manual of Purpose-Made Woodworking Joinery

Making basic mortise- and- tenon joints 27

Draw- bore Technique

Figures 3.14(a)(b): Dowelling used for draw- bore
dowels or pins (having replaced the archaic term
treenails or trenails) causes some confusion when
reference is made to ‘steel ’ draw- bore pins used by
joiners for initially testing the quality of the draw- bore
effect. The dowels are usually of 12mm Ø (diameter)
and should be the same timber species as the newel
posts. However, close- grained, straw- coloured Ramin
dowelling (a hardwood species commonly available
commercially) is often used for draw- bore dowels
on softwood newels. The dowel’s centreline position
should be marked on the newel posts at twice the
dowel’s diameter, i.e. 12 × 2 = 24mm from the shoul-
der. Vertically, this point should be in the centre of the
available tenon- height. After being carefully drilled
in the newel posts, the strings and handrails are fitted
(separately) – ensuring close- fitting shoulders – and
a 12mm Ø pointed auger- bit is inserted to mark the
tenon. After withdrawing the tenon, a second mark
is made 2mm towards the shoulder and a 12mm Ø
offset hole is drilled, as indicated in Figures 3.14(a)(b).

Mild- steel draw- bore pins

Figure 3.15: Because the jointing of strings and
handrails to newel posts must be fitted and checked –
stair- makers ideally require a pair of mild- steel draw-
bore pins to test the draw- bore effect. Illustrated below,
these pins are made from 11mm Ø mild steel and
need to be about 300mm long. One end is ground to
a conical taper and the other is bent over to assist in
withdrawing the pins after the joints are checked.

Fox- wedged stub tenons

Figures 3.16(a)(b): These traditional joints deserve

mentioning as, theoretically, fox- wedging is an excel-

lent way of strengthening stub- tenon joints – effec-

tively turning them into secret dovetails. But in reality,

they are not very practicable and I have never believed

that they have been used professionally to any great

extent. To be successful, the size of the wedges must

be carefully judged in relation to the degree of under-

cut slope at the ends of the mortise. Also, the length

of the wedges is critical. The marrying of the joint

can so easily fail if the wedges are too long, too short,

too thick or too thin. Also, when the wedges touch

down on the bottom of the blind mortise and pres-

sure is applied to close the joint and force the wedges

into the saw kerfs in the tenon, the wedges sometimes

move along the line of least resistance, causing them

to fracture and bend over sideways (indicated in

Figure 3.16(b)). This can obstruct the full entry of the

tenon. Finally, there is also a risk – as with all incisive

wedging that penetrates into the actual timber – that

the wedging/splitting action occurring in the tenon

will spread and appear in the rail itself.

MAKING BASIC MORTISE- AND-

TENON JOINTS

Having covered most of the fundamental technicali-

ties concerning mortise- and- tenon joints, I can move

on to the making of them. The detailed explana-

tions and illustrations here will mainly be to do with

the techniques involved in the use of hand tools (this

being usually regarded as the best foundation for

today’s trainee mechanized- joiners, wood- machinists

and DIY enthusiasts), but references will also be

made to the use of powered portable tools and fixed

Figure 3.14 (a) Horizontal

section through newel and

handrail showing draw- bore

technique; (b) Part- elevation

showing hole in tenon offset

by 2mm towards the hand-

rail’s shoulders.

NEWEL

POST

POST

NEWEL

DRAW-BORE

DOWEL

HANDRAIL

HANDRAIL

(a) (b)

Figure 3.15 Draw- bore pin.