Leigh D4R Pro, User Manual

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33
VARIABLY SPACED HALF-BLIND DOVETAILS
Chapter 10 D4R Pro User Guide
10-3 Joint Fit and Depth of Cut
Here’s why the depth of cut
➀
changes the fit in half-blind dove-
tails. Increasing or decreasing the depth of cut does not affect the
pin socket width
➁
, but does affect the width of the pin
➂
that
goes into the socket
➁
.
1
3
2
1
1
3
2
1
PIN
1
3
1
2
10-4
Note that decreasing the bit depth
➀
makes the pin
➂
nar-
rower while the pin socket ➁ stays the same width, producing a
loose fit.
Decreasing the bit depth (i.e. raise the bit into the router) pro-
duces a looser fit.
10-5
Increasing the bit depth ➀ makes the pin ➂ larger while
the pin socket
➁
stays the same width, producing too tight a fit.
Increasing the bit depth (i.e. lower the bit) produces a tighter
fit.
10-6 Bit Angle and Depth of Cut.
Half-blind pins and tails
are routed with the same dovetail bit, the same guidebush, and
the
same
depth of cut. A different depth of cut requires a differ-
ent angled bit. Leigh offers five different angled dovetail bits for
a range of cut depths. A lesser angle, say 8˚, for a deeper cut
➀
; a
greater angle, say 18˚, for a shallower cut
➁
.
1
2
18˚
8˚
10-7
Cumulative plus/minus tolerances in routers, bits and
guidebushes, make it impossible to state exact bit depth for first-
time precision fit. All dovetail jigs require trial and error tests to
attain fine fitting joints. The good news; we give a starting depth
for each bit. Test and measure the successful ‘Best fit’ depth of
cut
➀
or bit projection
➁
. Record for future first-time fits.
1
2
Depth
of Cut
Bit
Projection