The invention relates to a replaceable blade piece of a working cylinder of a screen crusher. A blade piece—has a frame portion and a blade portion, the longitudinally opposite front surfaces of which form work surfaces. The frame portion has a through hole extending in the longitudinal direction of the blade portion. A channel-like section is formed on opposite sides of the frame portion containing the hole and extends in the vertical direction of a frame portion, between the edge areas of the side with the hole. The invention further relates to a replaceable blade piece holder having a U-shaped frame portion including arm portions, through which extends a longitudinal hole of the frame portion, and a bottom portion. On the opposite surfaces of the arm portions, onto their middle area is formed a bulge, which extends in the vertical direction of the arm portion.