... Depth 0.5 0~0.7mm Nitrided Brittleness above 2 stage Surface Roughness Ra0.4 Screw straightness 0.015mm Hardess of ... of screw Gradual type,mutant type,wave type,barrier type,double screen type,shunt type,separation type,exhaust type,pin type,mixed type,double-head type,three-head type,multi head type etc. Specification ...