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Kerf in Laser Cutting: What It Is, Why It Matters

Kerf is the width of material the laser actually removes as it cuts. Your design says 'cut here'; the laser removes a strip about 0.1–0.3 mm wide centered on that line. For most signs and decorative cuts, kerf doesn't matter. For tight-fit parts — finger joints, inlays, mechanical assemblies — it matters a lot.

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Why kerf exists

The laser beam isn't infinitely thin. The focused spot at the focal point is typically 0.1–0.3 mm depending on the lens and material. As the beam moves along the cut path, it vaporizes a strip of material equal to that spot size.

When kerf matters

Finger joints, tab-and-slot assemblies, inlays, gears — anywhere two cut parts need to fit each other. Without kerf compensation, every tab is undersized by half the kerf on each side; every slot is undersized by half the kerf on each side. The cumulative slop adds up fast.

What Lazrit does about kerf today

Lazrit does not currently apply automatic kerf compensation. The exported SVG matches the design — the laser will remove its kerf inside the path. This is fine for signs and decorative work, but you'll need to compensate manually for tight-fit parts. Kerf compensation is on the Lazrit roadmap.

How to compensate manually

In Inkscape or LightBurn, offset all cut paths outward by half the measured kerf. Measure the kerf empirically by cutting two squares from the same sheet and measuring the gap between them.

fundamentalskerfprecision

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