comb jointing
with the DJ300
dovetail jig
he Trend DJ300 Dovetail Jig
has alternative template
options for cutting both
dovetails and comb joints. Fitted with
the comb joint template, guide bush
and 12.55mm straight two flute cutter
(Ref 3/76x1/4TC), 12.7mm (1/2 inch)
comb joints can be cut in either hard
or softwood from 12mm to 20mm
thick and up to 300mm wide. The jig
is easy to set up and with a little
practice, will cut precise and accurate
comb joints for boxmaking, cabinet
carcassing and furniture.
T
Timber preparation
Before setting up the jig, each side of
the box or carcass must be cut
accurately to exact widths in order to
produce equal thickness finger and
spacing across the width of the
workpiece. Each piece must also be
trimmed to the exact length required,
i.e. equal to the overall length of the
box sides. Unlike lapped dovetails
where two sides are cut short to
allow for the lap, with comb joints the
end of the comb fingers appears on
each face of adjacent sides.
Check that the ends are trimmed
square in both directions. Carefully
mark each side of the box (carcass)
to denote the face sides and each pair
of mating ends to ensure that each
piece is cut for assembly in the
correct sequence. Remember that
the widths of the prepared timber
24
INProfile
will be multiples of the pitch of the
template fingers.
Backing piece
To avoid cutting into the base of the
jig, always use a waste backing piece
at least 6mm thicker than the
workpiece. As each piece of the
joint is cut separately, this is fitted
into the jig in place of the horizontal
workpiece when cutting dovetails.
The backing piece should be of similar
width to that of each workpiece (box
or carcass side) and be fitted with the
forward end flush with the front of
the metal jig base. This prevents
break out on the back of the
workpiece as the joint is cut.
Positioning the
workpiece
Fit the two edge offset guides but
leave them slightly loose. Fit the
comb finger template to the jig so
that it sits flat and level on the
backing piece.
Clamp the marked workpiece to the
front of the jig with the top end flush
and tight against the underside of the
template. Ensure that the template
fingers protrude in front of the
workpiece and adjust the forward
adjustment nuts (fitted to the front
clamping bar threaded studs) so that
the front of the template is parallel to
the face of the vertical workpiece.
For the left hand edge guide, align the
2mm offset line against the left hand
edge of one of the template fingers.
Tighten the front clamp making sure
that the timber does not move. Use
a second workpiece to draw a line
across the top of the first workpiece
to denote the thickness of the mating
piece (i.e. the full depth of cut),
holding the second workpiece flat and
flush beneath the finger template.
On the front face of the first
workpiece or a trial piece of the same
dimensions, draw a centre line along
one face. Mark a 2mm offset to the
left and the right of it.
m t
2m ffse
o ine
l
m t
2m ffse
o ine
l
Autumn 1998