How to Set Up a Slitterhead for Three Perfect 355mm Cuts

One wrong blade position and your entire roll of material is scrap. Here is exactly how to set up a slitterhead to cut three strips of 355mm from an incoming web width of 1155mm — every number, every step. A slitterhead takes a wide roll of material — steel, film, paper — and slices it into narrower strips using pairs of spinning blades. Think of it like slicing a long sub sandwich into equal portions. Each blade pair has an upper knife and a lower knife that overlap slightly and pinch through the material like scissors, shearing it clean. Start with the width math. Three strips at 355mm each equals 1065mm of usable material. Subtract that from 1155mm and you get 90mm of total waste, split equally as 45mm of trim on each edge. That 45mm number anchors every blade position. Blade pair one sits at 45mm from the left edge; blade pair two at 400mm; blade pair three at 755mm. The remaining 45mm on the right falls away as trim. Now the two adjustments that determine cut quality. First, vertical overlap — how far the upper and lower blades cross each other. For standard medium-gauge material around 0.3 to 0.5mm thick, start at 0.5mm of overlap. Too much overlap creates heat and drag that dulls blades fast and deforms the cut edge. Dial it to spec, not just "enough to touch." Second, horizontal clearance — the tiny sideways gap between the blade faces. Set it to five to ten percent of material thickness. For 0.3mm material, that is roughly 0.015mm to 0.030mm, thinner than a human hair. Too wide gives a rough, jagged edge. Too tight scores and wears the blades. For setup: torque all arbor spacers to manufacturer spec, confirm both blade shafts are perfectly parallel with a dial indicator showing wobble under 0.02mm, thread the web, and set tension to ten to fifteen percent of the material's yield strength. A gap thinner than a human hair, held to a hundredth of a millimeter, repeated millions of times at speed, is the only reason that wide roll ever becomes something useful.