... 1,Surface Roughness :Ra 0.4 2,Screw Straightness :0.015mm Technical Specification1,Hardness After ... Than Grade 15,Surface Roughness :Ra 0.46,Screw Straightness :0.015mm7,Surface Chromium-Plating’s Hardness After ... Resistance Bimetal Spraying Process7,Horniness screw (HTP1:abrasion HTP2:corrosion resistance,HTP3:abrasion and corrosion resistance) Conical twin screw &barrel for plastic extruder