When it comes to laser-cut joinery, precision is key, and that precision hinges largely on the correct kerf settings. Kerf is the material vaporized by the laser beam during the cutting process. It’s like the width of the cut made by a saw blade, but for laser cutters, the width of the laser beam determines the amount of material removed.
Getting exact dimensions on a single piece of material isn’t particularly difficult, but joining two laser-cut pieces together poses a unique challenge. That’s why achieving a tight, potentially glue-free fit is my target. No matter the software you use, like Lightburn or any other laser cutting program, kerf adjustment is a standard feature. I will illustrate this using Lightburn as an example.

I will provide a file for laser cutting with ready-to-use components for plywood thicknesses of 3mm, 1/8″, 3.6mm, 4mm, 3/16″, 5mm, 6mm, and 1/4″. This file will allow you to fine-tune the kerf for the precise assembly of models.
Link to download the files: here
Load the file into Lightburn, select the components that correspond to the thickness you’re working with, and delete the rest. Assign a cut layer to them and double-click that layer to edit its settings. If it’s a cut layer (as opposed to an engraving layer), you will see a kerf adjustment option. Ensure this is enabled and set to a value appropriate for your laser cutter. This is the setting we’ll be tweaking each time we send a job to the laser. Every laser cutter is unique, so this setting will differ from machine to machine. For instance, I achieve quite good results with my laser using the following settings:
2.5″ lens: 0.095mm kerf width
3″ lens: 0.12mm kerf width
Now’s a good time to make a note of the settings you’re using.
Cut Your First Set
With your vector shape prepped and your kerf set to “on” with a specified value, send the cutting job to the laser. Don’t forget to check your power and speed settings to ensure they’re adequate to cut through the material.
After the cut, join the freshly cut pieces together to gauge the fit. Depending on your kerf setting, the pieces may be:
Too loose: Increase the kerf setting and try again.
Too tight: Decrease the kerf value and re-cut.
Just right: Congratulations if you’ve got it perfect on the first attempt!
A useful mnemonic for kerf adjustment is “Lower equals Looser.”
Document Your Results
I’ve performed this task enough times and forgotten my process mid-way to know that keeping notes on all settings for each cutting job is essential. It’s a bit of extra work, but it simplifies the process immensely. Just jot down your kerf value and note whether the fit was too loose, too tight, or just right.
Repeat the cutting process with new kerf settings until you achieve a snug fit. Once perfected, document your kerf value and material thickness for future reference.
Now, with the optimal kerf setting identified, you’re all set to create finely joined pieces with precision, whether for functional use or aesthetic pleasure.