Finger Joint Box Generator
Laser-cut boxes with finger joints — enter three dimensions, download the cut file.
Measure it. Nominal 3 mm ply is often 2.7–3.2.
A target. Adjusted so each edge takes a whole odd number.
Beam width. Tabs grow by this, slots shrink, so the joint ends up snug.
Cut a single test joint before committing a whole sheet. Thickness and kerf both vary between materials and between machines, and a box is six panels of the same mistake.
How it works
A finger joint — comb joint, box joint — interlocks two panels with alternating tabs. It is the standard laser-cut box because it needs no fixings, glues along a large surface, and self-aligns while the glue sets.
The whole thing turns on two numbers. Material thickness sets the tab depth, and it is not what the supplier printed on the sheet: nominal 3 mm plywood routinely measures 2.7 to 3.2, and a tab cut for 3 mm into a 2.7 mm slot is loose in every joint on the box. Measure the actual sheet with calipers.
Kerf is the width the beam burns away. Every cut takes half of it from each side, so a tab drawn at its exact size comes out one kerf narrow and a slot comes out one kerf wide — a joint with two kerfs of slop. This generator grows each tab by half a kerf on each flank and shrinks each slot by the same, so both land on the nominal size after cutting. Typical kerf is 0.1 to 0.2 mm on thin ply; cut a test strip and measure rather than guessing.
Each edge is inset by one thickness at both ends so corners stay clear, and the remaining span is divided into an odd number of fingers. Odd matters: it puts a tab at both ends of every edge, so each joint closes on a tab rather than a gap.
Common questions
Why is the fit loose or too tight?
Almost always thickness or kerf. Measure the sheet with calipers rather than trusting the label, then cut a two-piece test joint. Too tight means increasing kerf; too loose means decreasing it. Steps of 0.02 mm are enough to notice.
What does the finger width actually do?
It is a target, not a fixed size. Each edge is divided into the nearest odd number of whole fingers, so the real width differs slightly per edge. Wider fingers are quicker to cut and weaker; narrower ones glue better and take longer.
External or internal dimensions?
External is the outside of the assembled box. Internal is the usable cavity — pick that when the box has to hold something specific, and the generator adds two thicknesses per axis.
Which file do I want?
SVG for most laser software and for editing in Inkscape or Illustrator. DXF for CAD and for machines that want it. Both are 1:1 in millimetres, so nothing needs scaling on import.
Can I engrave or add a lid handle?
Not here — this generates the cut outline. Open the SVG in Inkscape and add whatever you like on a second layer.