The next time you need a sturdy, level work surface, I’ve
got the perfect solution for you: sawhorses and a pair of torsion
beams. Torsion beams are incredibly strong and will always be
dead straight; they’re easy to make and inexpensive.
But best of all for a crowded shop, torsion beams don’t take
up a lot of room. They're easy to store in a corner or on a rack.
You can make torsion beams in various lengths and just pull out
the size you need, when you need it.
What is a torsion beam?
A torsion beam is simply a narrow torsion
box–a structure that’s designed to resist bending
and twisting, yet be light in weight. It’s
based on the same engineering principles as
a skyscraper’s I-beams or the rails of a train
track. A torsion beam is composed of three
sections: a top and bottom, two sides, and a
series of web pieces inside.
This torsion beam is made from 1/2" MDF
and 1/4" tempered hardboard. Both of these
materials are fairly flexible, but when glued
together, the beam is almost as stiff as if it
were completely solid. This beam is 6" square
and weighs 3.3 lbs. per lineal ft. A 6' beam, for
example, weighs only 20 lbs.
What are torsion beams used for?
If you had a large, perfectly flat, rock-solid assembly table in your shop, you
probably wouldn’t need torsion beams. Got one? Well, most folks with small
shops don’t, either.
Placed on top of a pair of sawhorses, torsion beams are basically a knock-down,
modular assembly table. Torsion beams are ideal for a small shop because you can
store them in a corner or hang them on a wall and set them up whenever needed.
It’s best to have a few pairs in different sizes, from 4' to 8' long, so you don’t have to
take up any more space than your project needs.
To make a terrific worktable, place a piece of plywood or a hollow-core door
on top of the beams.
Make the beams from 1/2" MDF and 1/4" tempered hardboard.
Both materials are quite flexible–and that’s actually an advantage.
Unlike plywood, which can be warped, these materials will
stay flat and straight as you build the beams.
A simple requirement is the key to success: you must be able
to saw a straight line. To accurately cut large sheetstock, you
should have an outfeed roller or table behind your tablesaw. It
also helps to have a similar support in front of your saw.
The beams are 6" square and can be made any length you
wish. They’re best made in matching pairs, so you should cut
enough parts to make two at a time. I’ve found that pairs of 4',
6' and 8' beams fit all my needs. To build this set of three pairs,
you’ll need two sheets of MDF and two sheets of hardboard. But
even one pair, of any length, is handy to have around the shop.
Mill the parts
Begin by cutting the top and bottom pieces to length and width
(see Cutting List, below). Cut the side pieces to final size, too.
Cut 3/16" deep grooves to receive the sides (Photo 1). Make
them about 3/16" wide, using a standard blade. (The hardboard is only nominally 1/4" thick; its actual
thickness is usually closer to 3/16".)
Make the first pass on each piece with
the fence set 1" from the blade. Then,
move the fence approximately 1/16"
and cut a second set of grooves. Make
a few trial cuts in scrap stock to get
the correct fence setting–it's a fussy fit.
When you’re done, the sides should
drop into the grooves with little or
no resistance. Use featherboards to
ensure that the grooves are parallel
and have a consistent depth.
Next, cut the web pieces to width
and length. Their exact dimensions are
determined by the width and depth
of the grooves. First, rip one or more
blanks to width (Photo 2), then cut
the web pieces to length (Photo 3).
To make the beams comfortable
to handle, rout a 1/8" roundover
on all edges of the top and bottom
pieces. Check that all the sides fit
into the grooves (there may be some
variation in the hardboard’s thickness).
If one edge is too thick, sand
it with 80 grit paper until the piece
slides in the groove. Break all the
edges of the sides with 80 grit sandpaper
so they will be easier to fit into the grooves when you glue the
Mark the locations of the web pieces
on the bottom piece (Photo 4). Space
the outer web pieces 1" in from the
ends. Space the remaining web pieces
about 8" to 10" apart.
Create a level surface for gluing
the beams. The easiest way to do this
is to use one of the beams itself as a
gluing platform (Photo 5). This is an
important step. If you were to glue the
beams on a bowed or twisted surface,
they wouldn’t come out straight.
Place the bottom on the platform
and run a generous bead of glue down
both grooves (Photo 6). Next, drop
the sides into the grooves. Run a thin
bead of glue around all four sides of
each web piece, and stand them on
their lines (Photo 7). Run beads of glue
down the grooves in the top piece and
put it in position, starting at one end
(Photo 8). As you lower the top, the
sides will automatically align with the
grooves. Make sure the top is seated
along its full length by sighting down it
or placing a straightedge on it.
Clamp every 8" or so, or simply
place weights (bricks or cinder blocks)
on top of the beam.
Place a hollow-core
door on top of the
beams to make a
sturdy, flat table.
This story originally appeared in American Woodworker June/July 2010, issue #148.
June/July 2010, issue #148
Purchase this back issue.
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Click any image to view a larger version.
1. Cut shallow grooves in the top and
bottom pieces of the beams. The sides
should fit loosely in the grooves. Make two
sets of parts, to build a pair of beams.
2. Rip a blank for the web pieces. Make
it exactly the same width as the distance
between the grooves.
3. Temporarily assemble the top, bottom
and sides. Crosscut the web pieces so they
exactly fit between the top and bottom.
4. Disassemble the beam and mark
lines across the bottom to locate the web
5. Assemble one beam, without glue,
and turn it on its side. This creates a level
surface for gluing up the other beam.
6. Place the second bottom piece on the
clamped-up beam. Run a thick bead of
glue down both grooves.
7. Place the sides in the grooves. Apply
glue to all four sides of each web piece and
stand them in position.
8. Apply glue to the top piece and drop it
in place. The next day, use this beam as a
support for gluing up the other beam.