What dimensions do I enter in the generator, inside or outside?

Inside dimensions. That is the space for your content. The generator adds the material thickness on each side, so the outside is larger than the inside by twice the thickness.

Which thickness should I choose?

For small boxes up to about 150 mm, 3 mm plywood works well. For larger boxes, or ones that carry weight, 4–6 mm is stiffer. The generator supports 3, 4, 6, 8 and 10 mm.

What kerf should I enter?

Enter the kerf you measured on your own machine and material. Typical values are 0.1–0.25 mm in 3 mm plywood. If you do not know it, start at 0.15 mm and test a small box.

Should I glue the box or leave the joints dry?

A good friction fit holds fine for storage, but wood glue gives a strong, permanent box. Use a thin line of PVA wood glue and wipe off squeeze-out immediately.

What file do I use, SVG or DXF?

Both are exported. SVG is easy for LightBurn, Inkscape, Glowforge and xTool software. DXF is better when you work in CAD or when your laser software prefers it. Check the size after import either way.

Can I add engraving to the box?

Yes. Open the exported file in your editor, add your design on a separate engrave layer on the lid or a side panel, and keep the cut layer untouched.

How to Make a Laser Cut Finger Joint Box (Free Generator)

There is a special kind of joy when the last side of a laser cut box slides into place, with a soft push and a small click, and the whole thing suddenly becomes a box. It is also a special kind of frustration when it does not. The difference between the two is almost always one number: kerf.

This guide takes you from an empty screen to a finished laser cut finger joint box, using our free box generator. You will learn which numbers to enter, how to export, how to cut, and how to fix a fit that is a little off.

What is a finger joint box?

A finger joint (also called a box joint) is a row of interlocking rectangular tabs and slots along the edges of two panels. Each finger on one panel slides into a gap on the other, and the panels lock at a right angle without screws. Laser cutters are perfect for this because the joint is just a cut outline, accurate to a fraction of a millimetre.

A finger joint box has six panels: front, back, left, right, bottom and a lid (or a version without the lid). Everything lies flat on the sheet, so one sheet can often give you several boxes.

How our box generator works

The box generator is built for exactly this job, and it is free.

Setting	What you enter	Notes
Width, depth, height	Inside dimensions in mm	The space inside the finished box
Thickness	3, 4, 6, 8 or 10 mm	Measure your real plywood with a caliper
Kerf	0 to 0.4 mm slider	Your measured kerf; outlines are offset outward by kerf/2
Lid	On or off	Adds the lid panel
Export	SVG or DXF	Cut paths ready for your laser software

Because you enter the inside size, the box holds what you planned for. A 100 × 60 × 40 mm inside box in 3 mm plywood will be 106 × 66 × 46 mm outside, because there is one thickness of wood on each side.

Why kerf is in the generator

The laser removes a thin strip of material along every line. Without compensation, that makes tabs slightly smaller and slots slightly bigger than drawn, so the joint gets loose. The generator compensates by offsetting each outline outward by half of the kerf you enter, so tabs end up the right size and slots end up the right width. If you do not know your kerf, read how to measure kerf first. It takes ten minutes.

Step by step: from numbers to a finished box

Measure your material. Use a caliper. Nominal 3 mm plywood is often 2.8–3.2 mm. Choose the closest thickness in the generator (3, 4, 6, 8 or 10 mm) and note the difference.
Decide the inside size. Measure whatever goes in the box and add 2–3 mm to each dimension for clearance.
Enter the kerf. Use your measured value. For a first try with 3 mm plywood on an unknown machine, 0.15 mm is a reasonable guess.
Choose a lid, if you want one.
Export SVG or DXF. SVG imports into LightBurn, Inkscape, Glowforge and xTool Creative Space. DXF works in CAD tools and LightBurn too.
Check the size. After import, confirm the panel size in your software. If the file scaled by accident, see how to scale laser files correctly.
Set your layers. Assign cut settings to the outlines, with the right speed, power and passes. For 3 mm plywood see LightBurn settings for 3 mm plywood.
Run a test. Cut a small box first (for example 40 × 40 × 30 mm inside) on scrap before you commit a large sheet.
Dry fit every panel before you glue.
Glue and clamp. Thin line of PVA wood glue on the fingers, assemble, wipe off squeeze-out, and clamp with rubber bands or tape for 15–30 minutes.

Pro tip: Cut a small test box with your standard settings every time you change material or sheet batch. A sheet of plywood from a new supplier can differ by 0.2 mm in thickness, which is enough to change the fit from snug to loose.

Choosing the thickness

Thickness	Good for	Notes
3 mm	Gift boxes, small organisers, jewellery boxes up to about 150 mm	Most popular, cuts fast, even on diode lasers
4 mm	Medium boxes, desk organisers	Good balance of looks and strength
6 mm	Large boxes, storage, toolboxes	Slow on diodes; may need several passes or a CO2
8–10 mm	Heavy-duty or rustic boxes	CO2 territory, wider kerf and edge taper

Check what your laser can actually cut. A 10 W diode does not cut 6 mm comfortably, but a 40 W CO2 does it in a pass or two. See laser cutting plywood for types and thickness.

What a snug fit feels like (and how to fix the rest)

A good finger joint goes together with firm finger pressure, stays together without glue, and does not leave visible gaps. Use this table to tune.

What you see	Likely cause	What to change
Fingers need a hammer, wood splits	Kerf set too low, or plywood thicker than selected	Raise kerf by 0.02–0.05 mm, or choose a thickness that matches
Fingers slide and fall apart	Kerf too high, or plywood thinner	Lower kerf by 0.02–0.05 mm
Some joints tight, some loose	Uneven focus or warped sheet	Flatten the sheet, refocus, cut again
Gaps at the corners	Burnt and charred edges	Reduce passes, use air assist, sand lightly
Panels bow in the middle	Thin plywood on a big box	Use 4 or 6 mm for large panels

Common mistake: Leaving kerf at 0 on the first run and then blaming the plywood. Zero kerf only suits a laser that cuts with practically no loss, which does not exist. Enter at least a realistic value.

Add a lid, decoration and finish

The lid option gives you a panel that closes the top. For a hinged or sliding lid, you can modify the exported file in your editor. Decorations are easy: open the SVG in your software, add your engraving on a separate layer (black fill for engraving, red hairline for cuts, like our ornaments), and keep the generated cut paths intact. A hearts pattern on the lid or a name on the front turns a plain box into a gift.

For the finish, lightly sand the edges, wipe off the char with a damp cloth, and then add oil, wax or clear spray. If you plan to put in food, use food-safe finishes and check local rules for food contact.

Mistakes people make with finger joint boxes

Entering outside dimensions when the generator wants the inside.
Forgetting that plywood thickness varies from the label.
Cutting the sheet with the grain so that thin fingers are fragile and snap off; keep the longest finger rows across the grain if you can.
Scaling the file after export, which changes joint sizes. Never resize a finished box file.
Not testing on scrap.

Pro tip: Leave 2–3 mm of spare room around your content. Boxes that are exactly the size of what goes inside look smart, and annoy you as soon as the item has a case or sticker.

Ideas for boxes you can make today

A finger joint box is a small project with a big payoff. Because the generator accepts any inside size, you can build exactly what you need.

Box	Rough inside size (mm)	Thickness
Tea bag or jewellery box	100 × 70 × 40	3 mm
Pen and desk organiser	120 × 80 × 90	3–4 mm
Gift box for an ornament set	130 × 130 × 40	3 mm
Card deck box	95 × 65 × 25	3 mm
Small tool box	250 × 150 × 100	4–6 mm

Our ornaments fit nicely inside: the reindeer ornament is 90 × 124 mm, so a 100 × 135 mm inside box holds it flat, and a few cut-and-engraved pieces become a boxed gift set.

Fitting several boxes on one sheet

If you cut several boxes, arrange the panels tightly to save plywood, leaving about 2–3 mm between parts. Nesting software does this automatically and can save a good share of your material on production runs.

Next step

Open the box generator, enter a small box such as 80 × 50 × 30 mm inside, 3 mm thickness and your kerf, then export SVG and cut it from scrap plywood. When the joints click, scale up to the box you really want.