... style hole, the sleeve material adopted wear-resist 1.1 Screw: The screw diameter Φ62.4 mm, L/D=40 1, designed ... toy bricks principle. The material of screw core axle is 40 CrNiMoA, the material of screw element adopted high speed tool steel ... : 6WMO5Cr4V2, with high temperature vacuum quenching heat treatment. The screw element and core axle is connected by involute structure with ...