INCRA Jig - Manual (Page 14)

14
Dovetail Variations
The drawings at right show several
variations on a standard equally spaced
dovetail joint. Although these joint
patterns look quite different from one
another, they all have one thing in
common. They are all made using the
same equally spaced dovetail template.
By learning the variations technique
described below, you can customize the
joint pattern produced by any template.
This technique works not only for Half
Blind dovetails as pictured, but also for
Box Joints, Through Dovetails and even
the Corner Post Dovetails. In general,
pattern variations can be designed by
observing a few simple rules.
Pin and tail board characteristics
Fig. 61 details the characteristics of a common pin and tail
board. This information is useful in trying to visualize a
pattern modification using the variations technique.
Select cuts to omit
Variations are created by OMITTING cuts on one half of
the joint, and then ADDING them to the other half of the
joint. Layout the board on the full scale dovetail pattern on
page 16 to help you decide whether to omit cuts from the
pins or the tails. Leaving cuts off of the tail side, for
example, creates wider tails, Fig. 58. Leaving cuts off of
the pin side creates wider pins, Fig. 59. Although a bit
more complicated, cuts can be left off of both sides of the
diagram, resulting in a pattern variation that has both wider
pins and wider tails, Fig. 60.
Always modify the pattern symmetrically
For example, if you decide to omit the first two “A” cuts on
your stock’s width, you should also omit the last two “A”
cuts.
Cut the joint
Any cuts omitted from one half of the joint will be used to
modify the other half of the joint. If you decide, for
example, to omit cuts 2A and 7A when you are cutting the
“A” series of cuts on the first half of the joint, JUST ADD
cuts 2A and 7A to all of the “B” series of cuts on the
second half of the joint to automatically produce the proper
mating fit. It’s really that simple, give it a try sometime.
Dozens of pattern variations are possible for each joint
type.
Fig. 57 Fig. 58 Fig. 59 Fig. 60
Fig. 62 Determine joint layout
L
C
Tails (open cuts on ends)
Pins (solid wood on ends)
Center of board is
aligned with “Center
Cut” on template.
Suggested Center Cut is 5A
Board to be cut
Fig. 61
Pins or tails?
Tail boards are always cut vertically,
clamped to the Right Angle Fixture
and have “open cuts” on the outside
edges.
Pin boards are cut horizontally and will
always have partial pins (solid wood) on the
outer edges of the boards
To determine pins and tails, align the center of the board with cut “5A” on the dovetail diagram on
page 16 and observe where the edges overlap the full scale joint diagram. This will determine which
series of cuts will be the pins, and which will be tails. Pins have solid wood on the outside edges, and
tails have mating open cuts on the outside edges. In this example, the pins are the “A” series and
the tails are the “B” series of cuts. Pins and tails are determined entirely by the width of the board.
IMPORTANT: Avoid just a “sliver” of solid wood on the outside edges of the pins. If necessary, use
a slightly wider board to allow at least 1/8” of solid wood on both edges of the pins.
Determine dovetail joint layout.
The first step in making ANY dovetail joint, whether it
be Half Blind, Sliding, Through or Corner Post is to
determine which half of the joint will be the pins and
which half will be the tails. Follow the instructions in
Figs. 61 and 62 to decide which series of template
cuts to use for each half.
1/8” minim
um