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The right-hand corner of the blade determines
the final tenon diameter. To increase its
longevity between sharpenings, you may
wish to "break" this corner very slightly.
Just draw it against a 4000x stone or 5µ
abrasive paper with one or two passes.
Troubleshooting
UNEVEN TENONS: This is usually
caused by one of two things:
1) An unsteady drill position while
cutting. Reduce your drill speed and
concentrate on holding the drill steady
while cutting.
2) Growth ring structure. If the corner of
the blade is cutting tangential to a very
consistent diameter growth ring, the
blade may peel that layer, much the
same way veneer is cut from a log.
This will result in uneven or undersized
tenons. An extremely sharp blade is just
about the only preventive measure.
U N D E R S I Z E D T E N O N S : They
usually indicate a blade that has been
advanced too far. This is most often caused
by loosening the blade clamping screw too
much, which allows the blade to ride up
on the plug gauge and bend slightly once
tightened against the gauge. When the
gauge is removed the blade will drop to its
unstressed position and produce undersized
tenons. Readjust the blade.
OVERSIZED TENONS: These usually
arise when cutting green wood, where some
compression takes place. When the tenon
cutter is removed, the tenon will spring back
to an oversize condition. Adjust the blade
using the gauge as you normally would, but
then back off the blade clamping screw just
enough to tap the blade in a bit further, then
retighten. Note that you can use this sprung
oversize tenon to your advantage, as it will
shrink as it dries.
S C A L L O P E D T E N O N S : Applying
excessive force while cutting the tenon
can result in the cutter advancing at a rate
fast enough to make the tenon look like
a coarse thread. Reduce the inward force
applied to the drill.
Continuing to rotate the tenon cutter
clockwise while withdrawing it from the
tenon can also cause the blade to cut on its
return pass, leaving similar scallops. This is
especially so on green wood, where some
compression may have taken place as the
tenon was being cut. Instead, pull the tenon
cutter off the tenon with the drill switched
off, either without rotating it, or by slowly
rotating it counterclockwise.
OFF-CENTER TENONS: Nothing can be
done about the most common cause of off-
center tenons – natural variations in wood
density and growth patterns.
PARTIAL TENONS: If the tenon cutter
starts cutting, then fades and eventually
stops cutting, this indicates that a minor
blade adjustment is required. Swivel the
blade to produce a thicker shaving.
UNEVEN GRIND WHEN RESHARPENING:
This usually happens when the blade bevel
is not held parallel to the belt or stone.
Adjust the jig until the bevel is parallel to
the belt or stone.
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