48 Joinery joints
And for those who want to use dowelled edges for this
reason – and have a dowelling jig and/or access to a
pillar drill – the following notes apply.
Machine- serrated beech joint- dowels can be pur-
chased, or you can make your own from readily avail-
able 1.8m lengths of hardwood or softwood dowel
rod. These will need to be cut into 65 to 75mm lengths
and their ends should be chamfered or rounded off.
Then the dowels need to be grooved to allow trapped
air and glue to travel up the dowels when the joint is
being made.
Dowel- grooving block
Figure 3.48(b): One way of doing this is to make a
dowel- grooving block from a short piece of hardwood
with a hole drilled through its length to receive the
dowels. Up to four screws are screwed into the block,
so that they just break through the surface radially
into the drilled dowel- hole, as illustrated. When the
pre- cut dowels are hammered through the block, the
sharp points of the screws score v- shaped grooves
down their length. Hammering more than two dowels
into the block, releases the first dowels that were
entered.
When the boards to be jointed have been face-
sided and edged, the dowel- positions should be set in
from each end by about the length of the dowels and
spaced apart by at least 225 to 300mm. These posi-
tions should be squared and marked across both edges
whilst the boards are held together in the vice or with
G- cramps; a short, central gauge line, made on each
face edge, bisects the squared pencil lines.
After being carefully jig- drilled or pillar- drilled
(to a few millimetres over half of the dowel’s length)
the holes should be countersunk slightly to remove
any burred fibres and to facilitate easy entry of the
dowels (especially if they are slightly misaligned).
To make the joint, place one board in the vice and
squeeze a small amount of PVA adhesive into each
hole. Tap in the dowels and wipe off the exuded
glue. Place the second board in the vice and squeeze
the glue along the edge and into the holes as before.
Then spread the glue with a brush to cover the entire
edge and bring the joint together whilst the board is
still in the vice. Knock the joint together evenly with
a claw hammer and a hammering/cushioning block
before laying the jointed boards onto pre- positioned
(masking- taped or paper- lined) sash cramps. Apply
even pressure and then wipe off the excess, exuded
glue and leave to set.
The diameters of dowel rod commercially avail-
able vary from 6mm to 25mm and are usually in
2.4m lengths. The diameter required for jointing a
particular thickness of board is as stated for dowelled
frame- joints, i.e. approximately two- fifths the boards’
thickness. Example: 20mm board ÷ 5 = 4, 4 × 2 = 8.
Therefore, 8 or 9mm diameter dowels needed for
20mm- thick boards.Biscuit jointing
Figure 3.49: Again, the initial procedures described
above for butt joints and dowelled- edge joints also
apply to biscuit jointing. The only difference, of course,
is that instead of pre- positioned dowels, so- called
biscuits are glued into snug- fitting, segmental- shaped
grooves, made with a portable biscuit- jointing
machine. Like dowels – but much speedier and
potentially more accurate – they reinforce and align
the boards being joined. Most biscuit jointers seem to
have good safety features and are easy to set up and
use.Figure 3.48 (a) Dowelled edge and opposite counter-
bored edge.
(a)100 mmex 50 mmex 50 mm(b)Figure 3.48 (b) Purpose- made, hardwood dowel-
grooving block.Side elevation Plan view