1
MAKING A TUSK TENON
FOR KNOCKDOWN FURNITURE
BY THOMAS RETTIE
In the Middle Ages, like today, peo- and bulky items such as tables were
ple sometimes needed portable put up when not in use. In the
furniture. While we tend to think workshop, a table might be moved
of medieval furniture as usually to where the light was best, or tak-
large, massive, and immobile, there en to market for use as a counter.
were many instances when furni- Even in death, prized furniture
ture needed to be broken down might be sent with the deceased to
and moved from place to place. In the afterlife, as with the Viking
the home, space was at a premium burial ship uncovered at Oseberg.
A 16th Century German work table with tusk tenon joints
(after examples in Jost Amman s  Book of Trades ).
Copyright 2002, Thomas Rettie
2 3
The problem in making portable technique called drawboring. In The use of tusk tenons dates back have no problem in making a tusk
furniture is in devising joints that drawboring, the holes for the peg to at least the Vikings, whose mo- tenon joint.
are strong when put together, but are slightly offset so that the peg bile society made knockdown
that are easily taken apart and re- will pull the joint tighter when it furniture a practical necessity. As in all woodworking, there are
assembled. Today we have a is driven in. As the wood expands While not widely adopted in En- many choices in the tools you can
profusion of temporary metal and and contracts over time, the peg glish joinery, keyed tenons are seen use to make a tusk tenon. If you are
plastic fasteners, but in a time can be driven further to keep the frequently on German furniture, using hand tools, you will need, at
when nuts and bolts had to be joint tight. The peg can also be particularly on boarded benches, a minimum: a saw and a well-
forged and cut by hand, economi- driven out, allowing the joint to be work tables, and counters. They honed mortising chisel. A
cal solutions were more limited. disassembled if necessary. are also evident in heavier framed marking/mortising gauge is also
construction, such as printing helpful in laying out the cuts, and
One solution is the tusk tenon. With a tusk tenon, a key is used presses, looms, and post-and-beam a brace and bit can speed things up
Also called a keyed tenon or instead of a peg to hold the joint buildings. Tusk tenons even made when removing wood from the
wedged tenon, the tusk tenon is a together. Not only is the key easier a brief comeback in the Arts and mortises.
kind of mortise and tenon joint to remove and replace, it also pro- Crafts movement of the late 19th
that uses a wedge-shaped key to vides added strength and stability and early 20th centuries. If you have access to power tools, a
hold the joint together. to the joint. Because the key is out- drill press or mortising machine
side the joint, tusk tenons can only can speed things along, but you
SKILLS, TOOLS, AND
SKILLS, TOOLS, AND
SKILLS, TOOLS, AND
SKILLS, TOOLS, AND
SKILLS, TOOLS, AND
In a common mortise and tenon be used with through-tenons (that will still need a chisel to cut the
MATERIALS
MATERIALS
MATERIALS
MATERIALS
MATERIALS
joint, a protrusion on one part (the is, joints where the tenon goes all sloping side of the mortise for the
tenon) fits into a hole on the other the way through and out the other key.
Tusk tenons require no particular
part (the mortise). Usually the joint side of the mortise).
skills beyond the ability to cut a
is then locked with a peg using a
mortise and tenon. If you have not
attempted one before, you will
want to try a few for practice be-
fore forging ahead with tables,
benches, and the like. Most basic
woodworking books will provide
instruction on mortise and tenon
joinery; in short though, you will
need to be able to cut a straight line
and make a square hole. When you
are confident with mortise and
Mortising chisel and
tenon joints in general, you should
mortising gauge.
Pegged mortise and tenon joint. Tusk tenon joint.
Copyright 2002, Thomas Rettie Copyright 2002, Thomas Rettie
4 5
For a strong joint (and less cursing I normally begin by making the
MAKING THE TENON KEY KEY-MORTISING THE TENON
MAKING THE TENON KEY KEY-MORTISING THE TENON
MAKING THE TENON KEY KEY-MORTISING THE TENON
MAKING THE TENON KEY KEY-MORTISING THE TENON
MAKING THE TENON KEY KEY-MORTISING THE TENON
when you cut the mortises), you tenon (others may start with the
will want wood with clear, straight mortise). The distance from the
I find it convenient to next make The mortise that will hold the key
grain and no obvious cracks or shoulder to the end should be long
the tenon key. The key should be must have approximately the same
knots. In general, hardwoods such enough to pass through the mor-
no more than one-third the thick- wedge-shaped profile as the key.
as oak and poplar are excellent, but tise with at least 4 or 5 inches to
ness of the tenon it will pass Hold the key against the side of the
I ve also had good results with soft- spare on the outside. You can al-
through. Ideally it should be just tenon and trace its profile, then
woods such as pine, fir, and ways cut it down later if you find
slightly thinner than the thickness carry the lines across to mark the
hemlock if they have a clear grain. it too long; it s much harder to add
of your mortising chisel. If the key outline of the key-mortise on top
wood back if it s too short.
is too thick, it may split the cheeks and bottom.
MAKING A MORTISE AND
MAKING A MORTISE AND
MAKING A MORTISE AND
MAKING A MORTISE AND
MAKING A MORTISE AND
of the tenon.
When making a through-mortise,
The key-mortise should be placed
TENON JOINT
TENON JOINT
TENON JOINT
TENON JOINT
TENON JOINT
it is a good idea to cut in from ei-
The key is wedge shaped; straight slightly closer to the shoulder of
ther side to avoid tearing or
on the inside edge and tapering on the tenon than the depth of the
Begin by making the mortise and
splintering. A useful rule of thumb
the outside, with the grain running mortise, so that the key will pull
tenon joint. The particulars of this
is never to cut a mortise that is
the length of the key. The top of the the shoulder towards it when it is
joint will of course depend on the
more than one-third the width of
key can be flat or rounded (round driven in.
piece of furniture you are making;
the stock you are working with.
will be less prone to splitting). In
the examples shown below are for
general, the longer the key, the
the trestle table shown on page 17.
Depth of
more stable the joint will be.
Mortise
Shoulder
Key-Mortise
Shoulder
Grain
Mortise
Tenon
Tenon Key Tenon with Key-Mortise
Copyright 2002, Thomas Rettie Copyright 2002, Thomas Rettie
6
Assembled Joint Tusk Tenon Used with a Bed Rail
VARIATIONS
VARIATIONS
VARIATIONS
VARIATIONS
VARIATIONS
There are variations of the tusk If using horizontal wedges, use two
tenon that can be used when the key-mortises per joint to prevent
tenon is too thin to accommodate  racking (that is, where the joint
a vertical key. Instead, pegs or hor- is no longer perpendicular). Either
izontal wedges can be used, taper the key mortises to match
although this is usually a less se- the wedges, or use two wedges
cure configuration. (one from either side) per mortise.
Joint with One Wedge per Joint with Two Wedges per
Key-mortise Key-mortise
Copyright 2002, Thomas Rettie