Single Screw for Extrusion Machine Hardness after hardening and tempering HB240 â?? 280 Nitride hardness HV850 â?? 1000 Screw Diameter Φ20mm-Ï?250mm Nitride Brittleness less than grade 2 Hardness of nitration HV900-1060 (HRc56°-65°) Screw straightness 0.015mm/m