Glossary · Technology
Kerf
The width of the material the laser burns away when cutting. It decides whether slot joints and puzzle pieces fit together precisely.
Explained in more detail
Kerf is the width of the cut. It depends on the focus spot, power, speed, material thickness and the material itself. With hobby lasers it is typically between about 0.1 and 0.3 mm in wood and acrylic. Because the beam is cone-shaped, the cut in thick sheets is often wider at the top than at the bottom. Without compensation, outer contours come out smaller by half the kerf and holes come out larger by half the kerf. In the software you compensate with a kerf offset, which shifts the path outwards or inwards by half the value.
Where does the term come from?
Kerf is an old English word for the cut of a saw and the width of the material removed by it. The term was transferred from sawing to laser, waterjet and plasma cutting.
In practice
- Measure the kerf yourself: cut ten strips of equal width, measure the total width and divide the shortfall down to a single cut.
- For push-fit joints, enter half the measured value in the kerf offset, not the whole value.
- The kerf changes with every material and every setting. Store the value per material and thickness in your material library.
- Thicker sheets easily get slanted edges. For exact fits, a focus set slightly lower helps.
Not to be confused
Kerf is not the focus size: the kerf is usually wider than the focus spot, because the material also burns or melts beside the beam.
Frequently asked questions
How wide is the kerf of a laser?
For diode and CO₂ lasers in wood and acrylic, usually 0.1 to 0.3 mm. It depends strongly on the material, thickness and settings, so it is worth running your own test.
Why don't my laser-cut connectors fit?
Usually the kerf compensation is missing, so tabs are too small and slots too large. Measure the kerf and enter half the value as the offset.