Method of chopping unwound items

A method of separating long lengths of unwound item(s) selected from the group consisting of fibers, fiber strands, string, yarn, wire, tape and ribbon into segments of at least 25 mm long comprising feeding one or more said item(s) in an unwound form into a chopper at a speed exceeding about 305 MPM comprising a rotatable backup roll having an elastomeric peripheral working layer with a peripheral working surface and a chopping width on the peripheral working surface, a rotatable blade roll having a plurality of blades spaced apart around its periphery for contact with said unwound item(s) and into the peripheral working layer of the backup roll, the improvement comprising using a blade roll comprising a blade holder having a plurality of slots spaced apart around the periphery of the blade holder and a plurality of chopper blades spaced apart with one or more blade holding slots between each pair of chopper blades, each chopper blade residing in one of the plurality of slots in the blade holder, and a dummy blade slot filler, having a center portion and an end portion adjacent each end of the center portion, located in each of the slots between each pair of chopping blades, each dummy blade slot filler comprising a slot filler section in the center portion of a length of the dummy blade slot filler having a height that is equal to or within about 0.5 mm of the depth of the slot it is intended to fill, the length of the center portion being at least as long as the chopping width on the peripheral working surface on the backup roll of the chopper that the dummy blade slot filler will engage when used to chop said item(s), each dummy blade slot filler having a chopping blade edge and a tapered section on each end portion of the dummy blade slot filler, and chopping said item(s) into lengths of at least about 25 mm.