Understanding Kerf: How to Account for Material Loss

Kerf is one of the most important concepts in laser cutting, and understanding it will save you frustration and failed parts. Kerf is the width of material that the laser removes as it cuts—typically 0.003" to 0.005" depending on material, focus, and laser settings. For most projects, kerf is negligible. But for precise assemblies or fitted parts, accounting for kerf is essential.

What Is Kerf Exactly?

The laser beam has finite width. As it follows a cut path, it removes material from both sides of the path. This removed material is kerf. For a 0.004" kerf on a cut, the total material removed is 0.004", but it's distributed across both sides of the path (0.002" on each side). Understanding this distribution helps you design accurately.

When Kerf Matters

For simple cuts or engravings, kerf is invisible—you'll never notice it. But if you're designing interlocking parts, dovetail joints, or pieces that need to fit together precisely, kerf affects dimensions. If you design a slot to be exactly 0.250" and kerf removes 0.004", the actual slot opening will be 0.246"—half a kerf on each side. If a tab is designed to be 0.250" and kerf removes 0.004", the tab will be 0.254" (kerf adds to each side). Parts won't fit as intended.

How to Account for Kerf

There are two approaches. First, test on prototype material with your specific laser and settings. Cut a few test pieces and measure. If you discover a kerf of 0.004", you now know how to adjust your design. Second, ask your laser shop upfront what their typical kerf is for your material and thickness. They can tell you and suggest design adjustments.

Kerf Direction Matters

When kerf is removed, does it come off the inside of your intended cut or the outside? For slots that something will fit into, kerf makes the slot slightly narrower. For tabs that fit into slots, kerf makes tabs slightly wider. Designing with this in mind prevents fits that are too tight or too loose.

Testing and Refinement

Always test fit before full production on precision work. Cut one set of parts and verify they fit as intended. Tolerance issues reveal themselves immediately. Once you've confirmed fit, you can confidently move to full production knowing parts will fit correctly.

Designing precision laser-cut parts? American Laser Cutter can advise on kerf accounting and help you achieve proper fits. Visit americanlaserco.com to discuss your specifications.