What Kerf means
Kerf is the material destroyed by the cut itself. On a fibre laser it is narrow — commonly in the region of 0.1–0.5 mm depending on material, thickness, focal position and assist gas — and it is not a constant, because a thicker section needs a wider kerf to clear molten metal.
Why it matters on the shop floor
Two consequences follow. First, the finished profile is offset from the programmed path by half the kerf, which the nesting software compensates for. Second, on a punched part the kerf becomes the clearance between punch and die, and that clearance is what controls the burr height and the edge quality.
In practice
Kerf matters most at the small end of a design. A hole or slot whose width approaches the kerf of the process cannot be cut cleanly, and internal corners are always finished with a radius equal to roughly half the kerf — a sharp internal corner is geometrically impossible to cut with a round tool.
What to remember
- Kerf widens with material thickness and with the amount of power needed to pierce.
- Internal corner radii on a laser-cut part are at least about half the kerf; design them larger and the corner costs nothing extra.
- Cut-edge quality, dross and heat input all move together with kerf — a tight kerf is usually a cleaner edge.