Introduction: Collapsible Z-Shaped Side Table
I had dim recollections of seeing a flat shape which folded into a stool, and which had been made from a single sheet of material. I couldn't find any images of the original, and have no idea where I first saw it, but this table design is an attempt at re-imagining that.
The piece is a small table of the perfect height to sit beside an easy chair and hold a book and a cup of coffee (other hot drinks are available).
The piece can also be opened up to a single piece of wood which can be hung on a wall. It is shown here clamped to a door as there wasn't enough wall-space to demonstrate the alternative.
Step 1: Design
I made a cardboard model of the table from a piece of board. It was cut with a penknife and was mainly to help me work out how the hinges in the wooden model would fold to form the table. I cut a tab in the full-length insert leg and made a slot in the top just to let it stand up on its own.
The piece felt quite stable, although the top and bottom surfaces were only parallel when the legs were stopped from sliding past each other. This told me that there would need to be some hardware fitted to prevent this movement.
When scaling up to the full-size test piece, I decided to make a tabletop of 500mm square, about twenty inches.
With a desired height of the same, the centre piece which forms the split leg would need to be sqrt(2) x 500mm, which is about 707mm, (28 inches), less reductions for the thickness of the top and bottom pieces.
Trying to work out the required length of the single leg, which is at a steeper angle made my head hurt, so I decided to cut that to length as required.
500+707 gives 1207 (without hurting my head). Since I had a spare piece of plywood which was 1224mm (48 inches) wide (standard sheet width), I decided to use that for the big piece which is cut into two U-shapes. This would give a table a couple of inches higher.
Step 2: Cutting the Big Hole
Tools and components (mostly) assembled, I laid out the cuts which would be needed. Since the overall width of the table was to be 500, making the two legs of equal width would mean 125mm (5inches) for each side of the U and 250mm (10 inches) for the centre.
Once the lines were marked, I used a jigsaw to cut along them. To give a perfect right angle at the corners, there had to be a plunge cut made in each side. This can be done with the jigsaw placed nose-down on the workpiece. Starting the saw, and slowly angling it down into the wood will result in an initial cut. It can go more smoothly if you start the first hole, then move the saw forward a couple of mm (1/8 inch) and go again. PLEASE SEE LESSONS LEARNED CHAPTER BEFORE YOU DO THIS!
Four initial cuts were made, then the short lines at each end off the cutout were worked and then the longer cuts.
Step 3: Hinging the Base and Top
A second piece was cut for the top, 500mm square. That was used as a template to determine where to cut the base/lag combo in two.
The line was marked with pencil and then one side of the piece was cut with a handsaw. While this was perfectly aligned by the intact side, a hinge was fitted to the gap.
Then the second cut was made and the second hinge fitted.
After that, the top was offered to the upper end of the U-shaped leg (actually more of an n-shape since it's upside down). The piano hinge was too long, so it was cut to an appropriate length and then screwed on.
Step 4: Trimming and Hinging the Leg
Now there is a Z-shaped collection of three pieces of timber hinged together.
That was laid on its side on the bench, and the length required for the single leg was measured. The roofing square was used to ensure that top and bottom of the table were at the same angle to the edge of the workbench, and then a couple of bits of scrap wood were used to get the right length.
The long piece cut from the inside of the two U-s was cut to length with a handsaw and then fixed to the base of the table with a couple of hinges.
Step 5: Leg Support Chock
That looks great, but since there's nothing to stop the single leg from sliding along the underside of the tabletop, don't put anything fragile on there.
The single leg will be receiving force transmitted onto the end of the plywood, so I glued a strip of hardwood on to the exposed edge to give a bit more structural strength and reduced frangibility.
Once the glue was set and the edges trimmed and planed, a chock was fixed to the underside of the tabletop to secure the single leg, and the table could now sustain load without the leg collapsing.
Step 6: Anti-Wobble
The X-shape of the stand means that there is one position in which the tabletop is parallel to the ground (good) and an infinity of positions in which it is not.
To hold the legs in place, I used a couple of door bolts. Since the angle at which the legs cross each other is arbitrary, the bolts had to be round in cross-section.
Set the table on a surface which is already confirmed to be horizontal. Place a level on the tabletop and adjust until the level reads flat once again. Offer up the bolt and mark the screw holes.
Once the first bolt is fitted, the second is aligned with it.
Once both bolts and receivers are fitted, test it out. The two triangles formed by the crossing legs give a strong and stable platform.
All done, except for the confessions.
Step 7: Mistakes Made and How to Avoid Them
Using a jigsaw and plunge cuts to extract the long oblong from the middle of the base/split-leg piece meant that there was minimal waste. But since the long oblong is going to be shortened for use, there is no need to preserve every inch of wood. The plunge cutting was difficult and made a mess of the surface (first photo above). If I were doing this again, I would use a circular saw and robust fencing to do a plunge cut, and to cut most of the way to the corners. The little bits left could then be tidied up with a jigsaw. The wider kerf of the circular saw would give plenty room both for the jigsaw, and for the single leg to move.
Alternatively, if someone with access to a CNC router would like to transcribe this design, then that would solve all sorts of problems. The single-leg chock could be a half-depth slot cut and the rest of the pieces would probably be more accurately cut.
Using a jigsaw for long cuts is a recipe for wobbly lines. The cuts were pretty straight, but as the single leg has to pass through the split leg while transitioning from flat to table, any wavering is a problem. I ended up running the circular saw along the long edges of the removed piece to straighten them up, taking less than a mm, but leaving a smooth, clean edge. (second picture above)
The aluminium saw guide which I used for cutting flexed (third picture above). This let the jigsaw wander and made a bit of a mess of the wood. I cleaned it up, but be aware that a guide which works perfectly with one saw (circular saw) may not work as well with another.
In fact, to summarise the above:- DON'T USE A JIGSAW. Please let me know what you did use though.
If you decide to make jigsaw plunge cuts, then tips would be to start both of the long side cuts at the same end so that the centre piece from there can be cut off and discarded. Also, one of the short side cuts can be made where a hinge will be placed, so put it there and then conceal the damage with the hinge (fourth and fifth photos above).
The sixth photograph above shows why you should think before you screw. I fixed the tabletop on upside. That was easily fixed but it did leave a load of screw holes to repair. The whole point of the design is that only one face of the plywood is on display if the table is hung on a wall.
All-in-all, it works. I was surprised at how heavy it was, which makes it awkward to carry about, especially when it is unfolded and flopping all over the place. Making it with CNC routing would give a neater solution (probably still as heavy unless some strategic cut-outs removed mass). The hardware used was cheap (mostly from the two-dollar shop) and so doesn't look great. The concept worked, and I am glad that I remembered it and proud that I managed to re-engineer it.