Remove the template and slide the
left hand edge offset guide against the
edge of the timber and tighten the
screws. Repeat the setting up
operation for the right-hand side edge
guide using the right-hand offset line.
The offset guides allow each
successive workpiece to be quickly
positioned without the need to mark
the centre and offset line on them.
Setting the depth of cut
With the router disconnected from
the power source, fit the guide bush
and cutter. Stand the router on the
template with the guide bush spigot
between two template fingers. Ideally
using a fine height adjuster fitted to
the router, set the bottom of the
cutter fractionally above the
horizontal depth of cut line
(previously drawn on the face of the
workpiece). When cutting hard or
abrasive timbers it is advisable to cut
to the full depth of the comb finger in
a series of steps not exceeding 3mm.
After cutting the joint, the cutter can
Using a home made jig
A simple home-made jig can be easily
made from MDF and softwood offcuts. This can be used with any size
router fitted with a suitable guide
bush (for example a 16mm guide bush
and a 6mm diameter two flute
cutter).
The fixed batten shown on the
underside of the jig matches the
comb joint width precisely, in order
to space out the fingers on each
subsequent pass. A slot in the jig
allows the guide bush to track
precisely in order to cut each slot in
turn.
Autumn 1998
be lowered to the line for a final
trimming cut, or slightly below it to
allow for finishing.
Cutting the Joint
Connect the router and switch on.
Cut between each pair of fingers,
working from left to right. Repeat the
cutting operation on each end of each
box side. To ensure correctly fitting
and mirrored joint is obtained both
left-hand and right-hand edge guides
should be used.
Checking the fit
Assemble the joints dry to check the
fit before cutting the grooves for the
top and bottom of the box or cabinet
carcass. Remember that the grooves
to take the base and top panels (i.e.
thin plywood base and/or rebated
thicker panel), will show on the face
of the box on two sides unless they
are cut as stopped grooves.
Secure both pieces of wood
plus a backing piece in the
jig (the offset must match
the cutter diameter exactly).
Set up the router with the guide
bush and straight cutter and cut
the first finger.
Insert the template batten
into the first slot and
machine the second.
Repeat this procedur