I like to work on a large narrow table, piling up books, scarps of paper, writing implements, (plates, coffee mugs, etc.) all around me in either direction. And I like to give dinner parties. This table satisfies both needs—though you probably wouldn't want to spend a full day sitting on one of the benches. I use a padded chair with a back when I work.
I first saw a table that looked very similar to this in the basement cafeteria of Columbia University's School of Architecture, and I decided to steal their design. This is a reproduction of that table, as nearly as I could match it. Just who was the original designer, I can't say.
The table in the picture is 86" long, that was about as long as my dining room could tolerate, but the plans are for a 96" long table—the full length of a 4'x8' sheet of ply. You can adjust the length (and even width) as you please. NB: plywood sheets are not always square, so your dimensions may be reduced on that account. Try to buy square sheets.
The table stands a standard 30" tall and the benches — 17" tall. When not in use, the benches slide under the table, two on each side.
The whole ensemble is made out of 3 sheets of 4' x 8' Baltic Birch B-grade plywood (1" thickness, 17-ply), which will run you about $100 per sheet. (plywood info)
(Someone with a very keen eye might object that the benches in the picture are made of 3/4"-thick ply. This is true—it's what I had on hand, but using 1" ply throughout is easier, cheaper, more uniform, and that's what the plans call for.)
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Step 1: Cut Your Plywood
From the 1st sheet of plywood you will cut:
1 Table Top, 96" x 29"
12 planks of 23" x 3"
9 planks of 29" x 3"
The planks will be used to make the square "legs" of the table (3 more long planks will be cut from the 2nd sheet).
From the 2nd sheet cut:
3 planks of 29" x 3" (remaining "legs")
3 planks of 94" x 3" (crossbeams joining the legs and supporting the table top)
48 planks of 32" x 2" (bench "legs")
Step 2: Cut Your Plywood — Pt 2
From the 3rd sheet:
48 planks of 43" x 2" (bench tops)
Notes on cutting:
1. Remember that every cut will "cost" you about 1/8"—the width of a saw blade. This is why in the 3rd sheet the last two planks are cross-cut: although the sheet is 48" wide it can't in reality accommodate 24 2-inch planks.
2. Generally I like to do the rip cuts first, then the cross cuts. This minimizes your cuts on the table saw, and so reduces the chances of error. But in the case of the third sheet, be sure to do the cross cut first—you'll need those two cross-cut planks! Then rip away the remaining 2" planks.
Step 3: Glue-up—benches
— Take 12 planks of 43" x 2" and stand them on edge, staggering them two by two, as shown in the picture. The offset on each side will be 2" deep; the total width of the bench will be 12" (12 planks, each 1" wide).
— Glue the 12 planks together into a staggered or jagged-edge slab, measuring 45" x 12" x 2".
— Repeat 3 more times — to make 4 slabs of above dimensions.
— Repeat 4 more times with the shorter "leg" planks of 32" to make 4 slabs of 34" x 12" x 2".
Notes on the glue-up
Your offset must be very precise or the joint will be sloppy. To keep the planks from slipping laterally (and they will slip as soon as you apply pressure on the clamps)—make "brackets," as shown in the picture. Then, in addition to the 3-4 perpendicular clamps, you can add 2 long parallel clamps.
Brackets can be made from scrap wood, but they should be at least 1" thick, to keep them from buckling when you tighten the clamps, and at least 12" long to match the "teeth" of the bench slab.
Cut the 2" x 2" "inverse teeth" into the bracket with a dado blade.
To keep the bracket from sticking to the bench slab during the glue-up, line the inside of the bracket "teeth" with clear tape. Make several brackets so you're not waiting half an hour for every glue-up.
Once you have 8 bench slabs — 4 x 45" x 12" x 2" and 4 x 34" x 12" x 2" — scrape off the excess glue on the top and bottom. The individual planks may have shifted out of vertical alignment during the glue-up. If you have access to a robust planer, put your slabs through it to make sure the surfaces are perfectly even. If a planer is not in the cards, use a hand plane or a belt sander. Be careful with a hand plane — since it is very easy to chip the individual plies.
Step 4: Cut the Bench "legs"
Cut the 4 shorter "leg" slabs in half, as shown in the picture. This will give you 8 slabs 17" x 12" x 2" — flat on one end, jagged on the other.
Note on the cutting:
To get a square cut, this should be done on a table saw with a sled. If you don't have access to a sled, it may be better to cut the individual planks to size before gluing the slabs: instead of 48 planks of 32", you will cut 48 planks of 17" and 48 planks of 15"—then glue these into 8 slabs—flat on one end, jagged on the other—of 17" x 12" x 2. (See next step for picture)
Step 5: Glue the Benches
A very simple box joint glue-up—but you want it to be perfectly square, or you will get a wobbly bench.
To fine-tune the leg-to-top alignment: in addition to clamps running parallel to the bench top, add 2 (very long!) clamps, running on the diagonal, criss-cross, as in the picture (only 1 clamp shown). This will allow you to pull in the legs a bit, since their natural tendency will be to go out. Keep checking the square alignment of legs to top with a trusted square.
Once all the benches are glued you will want to sand the fairly rough surfaces created by the plywood edge. Level the "mortises" if they stick out with a belt-sander. Then use an orbital sander and go through the grits—up to 300 or even 600 for the seating surface. Finish with finishing oil (tung oil with drying agents).
You will also want to round all the edges (including the ones that touch the floor—it will protect the floor and make the bench easier to slide around). The best way to do this is with a router and a roundover bit.
Step 6: Assemble the Table "legs"
— Take a plank measuring 23" x 3" and cut in it three dados—1" wide by 1 1/2" deep—at either end and at the midpoint, as shown in the picture.
— Take a plank measuring 29" x 3" and cut in it three corresponding dados, 3" from either end and at the midpoint, as in the picture.
— Repeat once more for a shorter plank and once for a longer plank.
— Glue up a "sandwich" of 1 short planks with dados, 1 long plank with dados and 1 short plank without dados, as in the picture. Repeat.
Note on cutting dados:
To minimize tear-out from the dado blade: place a piece of scrap wood or ply behind the piece you are cutting, this will prevent to some extent tear-out on the exit side.
Note on the glue-up:
It would be too much trouble to make a special bracket for this staggered glue-up, but you do want to be absolutely sure your planks don't slide laterally, and that in the end you will have a 3" tenon on either side. One way to keep your boards straight is to mark off three inches on either end of the longer plank, and keep a close eye on them.
Step 7: Assemble the Table "legs" — Pt. 2
Now use the rest of the table-leg planks to make 3-plank staggered "sandwiches": long-short-long and short-long-short.
You've already made two short-long-short "sandwiches" so you'll have 2 more of those to go, plus 4 long-short-long. See picture.
Now, glue together the table's "leg squares." See picture. You will end up with two squares: 29" x 29" x 3".
Note on the glue-up:
Just as with the benches — to keep the square perfectly square use diagonally placed clamps and keep checking the interior right angles with a trusted square.
Step 8: Pre-drill Screw Holes
The square legs will attach with screws directly to the table top. (You could also use lag bolts—easier to turn towards the end. I used 4" long screws.)
Pre-drill holes in the top beam of each square for 6 or more screws, as shown (The top beam—i.e. the one that will go directly under the table top is the beam with the dados)
Repeat this step with the other leg square.
Step 9: Support Beams
— Take the three support beams, measuring 94" x 3" and cut out tabs 1 1/2" wide and 2" deep, corresponding to the dados in the legs. See pic.
— Stand the two leg squares 90" apart and drop the support beams into the dados. Pic. You will probably have to pound them in with a rubber mallet—make sure the beams go down all the way into the dado and their top edge does not rise above the beam. Your table top should sit on a perfectly even surface.
If you like, screw down the support beams—though this isn't necessary. In any event, I would advise against gluing them in, since you will certainly have to disassemble the table at some point.
Step 10: Attach the Top
— Place the table top face down on a flat surface. Turn over your leg-and-beam structure and align it perfectly with the table top. Pic.
— Screw down the legs to the top. (You may want to mark and pre-drill the holes in the table top first—this way the screw won't be pushing the top away. You want to get perfect contact between leg and top because a gap, however small, will be plainly visible).
— For added lateral stability you may want to add metal brackets (lower pic).
— To keep the outer support beams from being pushed in or out by wayward knees, attach them to the top, either by drilling obliquely into the top or with brackets or — as in the pic — by adding small strips of hard wood and screwing them down to beam and top.
Step 11: Finish
As with the benches — round all the edges with a roundover bit.
Sand the rough surfaces created by the ply edge—first with a belt sander, if your leg joints were not perfect, then with an orbital to 300. Sand the table top to 600 grit. Finish with lots of finishing oil—especially if this will be your dining table: plywood does not take kindly to spills, you want to seal it very well.