62 Making traditional and modern windows
sill and fixed with 18 or 25mm galvanized panel
pins at 150mm centres; 4) the box is cleaned up,
usually by sanding; 5) the parting beads – which
should be a tight fit into the grooves and not
require to be nailed – are cut to length and fitted
temporarily; 6) the staff beads are mitred and fitted
temporarily.MAKING AND FITTING THE
SASHES
Bearing in mind the theoretical positioning of
mortises and tenons – as covered in Chapter
3 – in reality, practical considerations have to be
considered and are often given precedence over
the theory. For example, the sashes’ mortise- and-
tenon positions shown in my scaled section views in
Figures 4.4(a)(b) and (c) are positioned off centre to
suit the 15mm rebate and 9mm ovolo mould required
on these stock sizes of sash material. And this also
affects the ideal one- third thickness of the mortise
and tenon, which has to be reduced from 11.33mm
(⅓ of 34mm sash thickness) to 10mm. But then, it is
not uncommon to adjust the tenon thickness to suit
the mortise.
Whether the sash members have been machine-
jointed or hand- jointed, they should be dry- assembled
and tested for a good fit. Then, with two sash cramps
per sash ready and aided by a glue brush and a damp
cloth, each sash is glued up speedily (to beat the
initial- setting time of 10 minutes) and cramped
immediately. The tenons and the inner ⅔ area of the
mortises are painted thinly with glue and quickly
assembled. Any oozed- out glue should be wiped
off with the damp cloth before placing the sash in
a pair of cramps and cramping up carefully, close to
each joint (with limited pressure to reduce the risk of
bowing the stiles). After speedily testing for square-
ness with a squaring stick, the wedges are glued and
driven in. This allows you to release the cramps whilst
the sash is lifted and sighted across to test that it is
out of wind. If in wind, place one end of the sash in
a vice and strain the other to correct it. Check again
and, after removing the twist, wipe off any excess glue
and place back in the cramps – if considered necessary.
(With relatively lightweight sash material, once the
glued tenons are wedged, this usually provides enough
mechanical key to hold the joints together until fully
set).
Whether you keep the sashes in cramps or not,
they should be carefully set aside for a period of time
to allow the adhesive to fully set. The manufacturers
of the hybrid resin adhesive mentioned above recom-
mend a period of 3 to 4 hours.ASSEMBLING THE BOXFRAME
After the four pulley wheels have been fitted and
screwed into the apertures in the pulley stiles, the
sequence of assembly always starts by gluing and
wedging the lower ends of the pulley stiles into the
sill- housings and then gluing and nailing (with 50mm
oval nails) the upper ends into the housings in the
pulley- stile head. Next, the assembled inner- frame
must be checked diagonally for squareness and sighted
from edge- to- edge to check that it is out of wind (not
twisted). The diagonal check is best done with a so-
called squaring- or pinch- stick with a preformed arrow-
pointed end. A length of parting- or staff- bead could
be used. With the frame lying outer- side down across
a bench, the pointed end of the squaring stick is posi-
tioned into an inner corner and the opposite diagonal
corner is marked. This procedure is then repeated on
the other diagonal of the frame and another mark is
made. If the marks coincide, the frame is square. If
there are two separate marks, make a central mark
between them and force the frame to meet it before
proceeding.
Next, because of the relative weakness of the
unframed pulley stiles on the pocketed- side, the
inner linings should always be fixed first. To achieve
this, glue is lightly run along the rebated edges of
the tongued pulley stiles (excluding the square-
edged pockets!), the pulley- stile head and the
recessed housings in the sill – and then the two
inner linings and the inner- lining head are quickly
positioned, hammered in on a protective hammer-
ing block and nailed at about 225mm spacing with
38mm oval nails, punched in below the surface by
about 2mm. The inner- lining head, having been also
glued on its shoulder abutments, is then adjusted
for flushness and a blunted 38 or 50mm oval nail is
skew- nailed from the head to the upright lining on
each side.
Following this, the frame is turned over on the
bench and a similar gluing and fixing procedure is
carried out in attaching the outer linings and head.
Finishing operations include 1) placing at least
six to eight staggered glue blocks (three or four on
each side) in the inner angles of the box’s open top,
to support and give vertical rigidity to the inner-
and outer- linings; 2) inserting the wagtails in the
pre- cut slots in the head (note that, as shown in
vertical section 4.1(b), at the start of this chapter, a
wooden peg or wedge should be inserted through
the wagtail to keep it suspended fairly loosely above
the boxed sill by about 50mm; whether a peg,
wedge or a nail is used, it must be reliably fixed,
as collapsed wagtails are irreplaceable in situ and
cause the weights to jam up); 3) the plywood back
linings are scribed to the approximate shape of the