material: 38CrMoAlA

B240-280 hardness after quenching and tempering

diameter: Φ15mm-Φ300mm

L/D: 4-35

HV900-1000 hardness after nitridation

0. 5-0. 6mm depth of nitrided layer

brittleness after nitridation: ≤second level

urface roughness： RaO. 4 u m

straightness: 0. 015mm/m

<0. 02mm inside&outside diameter tolerance

circular run-out≤0. 04mm

screw length tolerance≤O. 03mm

key& spine tolerance grade:Grade 7

Screw type:

Gradual type, mutant type, wave type, barrier type, double barrier type, shunt type, venting type, pin type, mixing type, double-start type, multi-start type, granulating type, etc.