Measure the kerf of a laser cutter without a caliper! Instructions: To determine the kerf of your laser cutter: How it works: The width of the gauge (in the file) is stepped, starting at the width of the hole and increasing 0.004" at a time. The difference between the (physical) width of the hole and the gauge is 4 times the kerf (once for each side of the hole, and once for each side of the gauge). When the gauge fits snugly, the extra width of the gauge exactly compensates for the kerf. Made proudly at i3 Detroit.