How the tabs work
You enter three things. The inside width, depth and height of the box, which is the empty space it has to hold,
and the thickness of your material. Makeabox draws the six panels of a closed box and cuts every edge into tabs.
Where one panel has a tab, its neighbour has a gap of the same size, so the panels lock together at every corner.
Woodworkers call this a finger joint or box joint. Some people say notches or teeth.
Because you give inside dimensions, the outside of the box is one material thickness larger on each side.
A 100 mm cube cut from 3 mm plywood measures 106 mm across.
Why every edge has an odd number of tabs
Makeabox splits each edge into an odd number of equal sections and alternates tab, gap, tab. With an odd count,
both ends of an edge start the same way, so the edge looks the same from either end. Turn a panel around and it
still fits.
That is why these boxes are easy to put together. A closed box has only three different panels. The top matches
the bottom, the front matches the back, and the two sides match each other. No panel can go in backwards or
upside down. A lid that lifts off adds a fourth shape.
Thickness
Measure the sheet with calipers in a few places instead of trusting the label. Plywood sold as 1/4″ is often
closer to 0.2″, and acrylic varies from sheet to sheet.
Tabs are exactly as deep as the thickness you enter. Enter too little and they stop short of the outside face,
leaving a step at every joint. Enter too much and they stick out past it. Tabs that stick out sand flush in a
minute. Short ones can't be fixed, so if your readings disagree, use the largest.
Notch length
Leave it blank and each tab is about three times the material thickness, which suits most boxes. If you enter a
length, Makeabox treats it as a target and adjusts it so a whole, odd number of tabs fills each edge exactly.
The tabs you get may be a little longer or shorter than the number you typed.
The length can be anything from 5 mm, about 0.2″, up to a third of the shortest side. That upper limit
means every edge gets at least three tabs. On a very small box the lower limit drops to half the upper one.
Kerf
A laser doesn't cut a line of zero width. It burns away a thin strip of material, usually 0.1 to 0.2 mm on a CO2
laser, and the width of that strip is the kerf. Cut a drawing exactly as drawn and every tab comes out a little
narrow and every gap a little wide, so the joints rattle.
Makeabox enlarges the drawing by the kerf you enter, so after the laser burns its line the parts come out the size
you need. A higher kerf gives a tighter fit. Wood handles a snug press fit well. Acrylic is brittle and cracks if
you force it, so aim for panels that slide together under firm hand pressure, then glue them.
Cut a test box first
Before you cut a large box, cut a small one from the same sheet with the same settings. If the panels fall apart,
raise the kerf a little and cut again. If you need a mallet to close them, lower it. Small steps of a few
hundredths of a millimetre make a visible difference. Write down the value that works for each material and
laser, and next time you can skip the test.
After you download
The drawing opens in LightBurn, Inkscape, Illustrator and CorelDRAW. Add holes for cables, switches or hinges, or
engraving, before you send it to the cutter. Keep holes clear of the tabs, because a hole that cuts into a tab
weakens the joint.
If you want to check the math, the
code that draws every box is open source.
makeabox