There are several methods of cutting nonwoven material; the two most common being shear slitting and score (sometimes called crush) cutting. The shear slitting method is similar to the way sissors work. The upper thin blade shears the fibers against a heavier bottom blade. Shear cut knives are more difficult to set properly because there are three settings involved. The knife holder is pneumatically operated and the penetration shown as “Y” in the drawing is adjustable. Once the knife lowers, it will move sideways a short distance to snug against the lower knife. It is important that the lower knife is set so that the upper knife engages it sideways so there is no gap left between the two blades. Lastly, there is an adjustment called “cant angle” as shown in the lower drawing. This angle is usually about 2 degrees. Without this slight angle, there would be no shearing action.
KNIVES ARE DANGEROUS—BE CAREFUL