1. Material: 65Mn or 50# spring steel 2. Heat treatment: HRC42-48 3. Finish: Oxidation treatment or Dichromate Plated.Thread size d ST3.9 ST4.8 ST6.3 Pitch p 1.4 1.6 1.8 d1 3 3.8 5 d3 5 6 7 l 16 20 25 20 25 20 25 W 12 13 13 e 9 12 18 12 16 14 t 0.4° - 0.04 0.6° - 0.05 0.8° - 0.07 K 1.8 2.8 1.8 2.8 1.8 2.8 1.8 2.8 1.8 2.8 1.8 2.8 Technical terms:Material: Mn65; Heat treatment: HRC42-48, Surface is to be oxidation
