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American Woodworker
NOVEMBER 2004
Copyright 2004. All rights reserved.
Torsion-box
construction creates
sag-proof shelves
that “defy” gravity.
Some time ago, an Ace Hardware ad in
American Woodworker
sparked a surpris-
ing number of inquiries from readers.They
all wanted to know how to build the cool-
looking shelves that appeared in the back-
ground. We liked the shelves, too. Their
contemporary design and invisible mount-
ing created a dramatic effect.
The secret was torsion-box construction.
A torsion box is a simple grid of slender
ribs glued between thin plywood skins. It
makes these shelves stiff and flat, yet
incredibly light. This rigid architecture
means torsion-box shelves won’t sag or
twist, and they can be mounted without
any external support.
We’ve made these shelves easy to build
and install by using simple shop-made jigs
and dividing the process into four steps.
We’ll make the torsion boxes, attach the
face moldings, then glue the C-shaped
units together and, finally, hang them on
the wall.To create the wall of shelves shown
here, you make four identical C-units and
hang every other one upside down.
We wanted our shelves to be a uniform
light color, so we chose hard maple instead
of birch. The cost is the same, but maple
lumber and plywood colors are easier to
match.The Multiply brand of underlayment
(available at home centers) makes great rib
stock, because it’s inexpensive, stable and
exactly 1/4 in. thick. We spent $220 to make
our four C-unit shelves.
Copyright 2004. All rights reserved.
American Woodworker
NOVEMBER 2004
37
by Tim Johnson
P
ROJECT
R
EQUIREMENTS AT A
G
LANCE
Materials for four C-units:
12 bd. ft. of 6/4 hard maple
15 bd. ft. of 5/4 poplar
Two sheets of 1/4-in. x 4-ft. x 8-ft. hard maple plywood
Two sheets of 1/4-in. x 4-ft. x 4-ft. underlayment
One sheet of 3/4-in. x 4-ft. x 8-ft. MDF
One sheet of 3/4-in. x 2-ft. x 4-ft. fir plywood
Cost:
$220 for four units
Hardware:
One box No. 9 x 1-in. brass screws
A handful of No. 6 x 3-in. drywall screws
Tools:
Tablesaw, 1/4-in. dado set, chop saw, jointer, planer, router, 1/2-in.
flush-trim bit, drill, plate jointer, wood glue, roller, clamps, level,
compass
F
IGURE
A E
XPLODED
V
IEW
D
ETAIL
1
Template
G5
7-1/4"
G1
7/8"
G2
D
3"
1/4" x 7/16" NOTCH
D
C
G4
C
G3
D
ETAIL
2
Molding Profile
C
Each C-unit requires three torsion
boxes. They’re all made the same
way, just in different lengths.
• Torsion box for upper shelf
1-1/4" x 9-3/8" x 34"
• Torsion box for upright
1-1/4" x 9-3/8" x 18-1/4"
• Torsion box for lower shelf
1-1/4" x 9-3/8" x 51"
45
°
BEVEL
1-1/4"
F3
F1
F1
5/16"
F2
1-1/4"
D
16"
#20 BISCUITS
45
°
MITER (TYP.)
1-3/8" W CAVITY (TYP.)
E2
E5
B
E1
C
A
E3
E1
D
E4
F
IGURE
B N
OTCH
-C
UTTING
J
IG
POLYCARBONATE
GUARD 1/4" x 3" x 7-1/2"
F
IG
. C
Box Beams
F
IGURE
C B
OX
B
EAM
MDF
7/16"
SLED
3/4" x 6" x 24"
18-GA. x 1-5/8" PIN NAIL
3"
FENCE
3/4" x 2-3/4" x 24"
1/4"
SLOT
MDF
INDEXING PIECE
1/4" x 7/8" x 8"
18-GA. x 1-5/8" PIN NAIL
38
American Woodworker
NOVEMBER 2004
Copyright 2004. All rights reserved.
B
UILD THE
T
ORSION
B
OXES
LEDGER BOARD
CAVITY
LONG
RIB
1. Cut the torsion-box skins (Fig. A, E1, F1 and G1,
page 38) from 1/4-in. maple plywood (see Cutting
List, page 45). To get skins for all four C-units from
two sheets of plywood, rip each sheet into five 9-1/2-in.
x 8-ft. blanks. Cut eight of these blanks into 51-in. and
34-in. skins for the shelves. Cut the eight 18-1/4-in. skins
for the uprights from the remaining two blanks.
2. Cut the sheets of 1/4-in. Muliply plywood underlayment
into 7/8-in. x 48-in. ribs (A).
3. Plane poplar edging stock to the same 7/8-in. thickness as the
ribs’ width. Cut the front and end edging pieces (C and D) to width
and length.
4. Build the notch-cutting jig (Fig. B, page 38).
5. Cut notches in the ribs (Photo 1). Butt the ribs against the index-
ing piece to cut the first notches. Use these notches to index the ribs so
BOTTOM
SKIN
TOP
SKIN
SHORT
RIB
SIDE
EDGING
FRONT
EDGING
HOLD-
DOWN
INDEXING
PIECE
TEMPLATE
LONG
RIBS
1
Cut notches in the ribs, using a shop-made indexing jig
2
Cut short ribs from some of the
BOX
BEAM
TORSION
BOX SHELF
TOP SKIN
3
Glue the torsion boxes together by sandwiching the
4
Clamp the torsion boxes between box beams. Box
Copyright 2004. All rights reserved.
American Woodworker
NOVEMBER 2004
39
and a 1/4-in. dado set. The notches allow you to assemble
the ribs into the grid sections that comprise the core of
the torsion boxes.
long ribs. Use a template
(Fig. A, Detail 1) and an
indexing piece to make sure
you cut them consistently.
beams distribute clamping pressure evenly and guaran-
tee your glued-up shelves will be flat.They’re well worth
the effort to make.
edging and the grid section between the plywood skins.
This is a complex glue-up, so use glue that won’t dry
too fast and a roller to spread it quickly and evenly.
M
AKE THE
B
EVELED
M
OLDING
RIDGE
5
Glue on molding blanks that are slightly thicker than the
6
Rout the edges flush. Use a second shelf to support the
router and a piece of scrap plywood as a spacer.
SUPPORT
FENCE
45
o
BEVEL
fence and make a second light pass to clean the edge.
8
Bevel the end molding with your miter gauge and a long
support fence. Rough-cut the bevel and then make a
light final pass.
Caution:
If your shelf and miter gauge are unstable in the starting
position because they hang off the front of the saw, use a sled to
make this cut (see “The Ultimate Shop-Built Crosscut Sled,” AW
#75, October 1999, page 38).
40
American Woodworker
NOVEMBER 2004
Copyright 2004. All rights reserved.
shelves. Make sure you feel ridges on both sides of the
blanks as you tighten each clamp, and again after all the
clamps are tight.
7
Bevel the molding. It’s difficult to get good results when
you cut thick, hard wood at an angle, so make two pass-
es. First, make a slightly oversize rough cut. Adjust the
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