One of the questions
most often asked about the Moravian workbench I
wrote about a
years back, concerns the tusk tenons (aka keyed
tenons) that are the backbone of the design.
The tusk tenons on the bench I built over four years ago have
performed flawlessly. That bench is still the one I use
primarily, it travels with me to classes and on other trips,
assembled and taken apart scores of times.
Nevertheless, the keyed tenon seem to have a not so great
reputation in the woodworking community. I think that this bad
reputation comes not so much from the older forms of the joint,
but from later times, more specifically arts and crafts
The early forms of the tusk tenon are generally much larger and
more robust. During the arts and crafts movement, starting in
the 1870’s, tusk tenon joinery appeared quite often on
bookcases, clocks, tables and chairs. Most of these were more
for decoration of the piece than structural. Most are made small
with a small amount of wood past the wedge.
Over time, the wedges would get loose, someone would drive
the wedge back in too tight and… Crack! The end grain of the
tenon would blow out. That’s my theory anyway. I am not trying
to knock art and crafts furniture, these small joints were fine
for a bookcase or clock. Really, how much thrashing does a clock
or book case get most of the time? Different story on something
like a workbench though.
I have not been able to find an exact date when this type of
joint came into existence. Most sources say the joint seems to
have originated in central Europe. As these folks immigrated to
the United States they of course brought knowledge of this type
of joinery with them. T
The Moravians (Old Salem, NC), from which this bench design
originates, came from what is modern day Czech Republic. The
oldest known mortise and tenon joint is of the keyed variety
excavated from a well in Leipzig, Germany. It was found to be
7000 years old.
What gives this type of joint strength and the reason it has
endured millennia, in my opinion is enough wood beyond the wedge
on the tenon (as the vintage ones are made) and as you will see
in the video the wedge itself.