What is kerf on a laser cutter?

Kerf is the width of material the beam vaporizes as it cuts — usually 0.05 to 0.2mm depending on the machine, material, power, and speed. It matters because it shaves material off both walls of a slot and both sides of a tab, which is exactly what leaves finger joints loose.

How do I measure my laser's kerf?

Cut a test comb from the exact stock you'll use, measure a slot with calipers, subtract the nominal width in your file, and divide by two. That's your per-edge kerf offset. Never pull a number off a forum — kerf changes with material, thickness, and cut settings.

What is a typical kerf for 3mm plywood?

On a 60W laser, 3mm ply usually lands around 0.10 to 0.18mm. Treat that as a starting point, not gospel — always verify on your own machine, because it varies by a lot.

Do I have to recalibrate kerf every time?

No. Store the offset against that machine-and-material combo once and the Box Maker applies it automatically on every export. Cut once, fit clean.

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LaserJune 18, 2026· JP T

Dialing in kerf for press-fit joints

A five-minute calibration that turns loose, rattly finger joints into a satisfying tap-together fit.

Every laser cuts a slightly different kerf — the width of material the beam vaporizes. Ignore it and your finger joints come out loose. Overcompensate and nothing fits at all.

Cut a test comb

Cut the calibration comb from the same stock you'll use for the real part. Same material, same thickness, same power and speed. Kerf changes with all of them.

Measure the slot width with calipers.
Compare it to the nominal width in your file.
The difference, divided by two, is your per-edge kerf offset.

Apply it once

Store the offset against that machine + material combo and the Box Maker applies it automatically on every export. Cut once, fit clean.

Rule of thumb: 3mm ply on a 60W laser lands around 0.10–0.18mm kerf. Always verify — your mileage will vary by a lot.

Frequently asked questions

What is kerf on a laser cutter?: Kerf is the width of material the beam vaporizes as it cuts — usually 0.05 to 0.2mm depending on the machine, material, power, and speed. It matters because it shaves material off both walls of a slot and both sides of a tab, which is exactly what leaves finger joints loose.
How do I measure my laser's kerf?: Cut a test comb from the exact stock you'll use, measure a slot with calipers, subtract the nominal width in your file, and divide by two. That's your per-edge kerf offset. Never pull a number off a forum — kerf changes with material, thickness, and cut settings.
What is a typical kerf for 3mm plywood?: On a 60W laser, 3mm ply usually lands around 0.10 to 0.18mm. Treat that as a starting point, not gospel — always verify on your own machine, because it varies by a lot.
Do I have to recalibrate kerf every time?: No. Store the offset against that machine-and-material combo once and the Box Maker applies it automatically on every export. Cut once, fit clean.