Manual of Purpose-Made Woodworking Joinery

Designing, setting out and making stairs 113

of the machined housing will have to be finished by

hand- chiselling techniques – i.e. vertical paring with

bevel- edged chisels and in- cannel scribing gouges.

String tenons and dowels

Figure 6.42: The stub tenons formed on strings for

insertion into the blind mortises in the newel posts,

seem to vary in depth from a half to two- thirds the

post’s thickness. I believe the latter is better. This is

because these tenons (used also for handrails) are usually

dowelled by a technique known as ‘draw- boring’ and the

grain of the shorter stub tenon (as illustrated in Figure

6.42) has a tendency to shear if the tenon is too short.

• after being marked out with tread- and riser-
  templates – were counterbored with three holes of,
  say 25mm Ø (diameter) near the nosings. This was
  done to facilitate the tenon- saw cuts after paring out
  the shaded portion shown above. The hand- router work
  was greatly relieved by chopping quite deeply across
  the grain with a firmer chisel and mallet – illustrated in
  section A- A.

Housing the strings by machines

Nowadays, the stair- string housings are done by a
variety of machines – apart from heavy- duty port-
able powered routers. Such machines include CAD –
CAM (computer- aided design and manufacture)
production and the use of CNC (computer numeri-
cally controlled) routers.

Using handmade jigs

Figure 6.40: The heavy- duty portable powered plunge-
router requires controlled guidance, either in the
form of patented stair- template jigs, as illustrated in
Figure 6.34(e), or in the form of hand- made plywood
jigs, such as that illustrated in position in Figure 6.40.
The jig is either clamped or pinned to the string at
each consecutive move – and requires its wooden side-
fences to be repositioned (turned over) for the jig to be
operational on the opposite (left- or right- hand) string.

Heavy-duty

plunge router

Plywood template

positioned on

stair string

1

2

Figure 6.40 A purpose- made left- handed plywood jig in
position on part of a stair string, with a portable plunge-
router shown above it.

Nosing- shape adjustment

Figure 6.41: If the required nosing- shape for the treads
is different to the semi- circular end of the routered
housings, as indicated in Figure 6.41, a small portion

Figure 6.41 The shaded area, which is marked from the

step’s profile after the routered housings are made, indi-

cates the portion of string to be shaped by chisel- paring.

* sheared

tenon-ends

Twice dowel-diameter=12×2=24 mm

of newel

*

*

(^2) ⁄
3
(^1) ⁄
2
Figure 6.42 Sheared ends of stub- tenons can be caused
by draw- bored dowels if the tenons are only half the thick-
ness of the newel post.