Shaft material: Seamless high tensile pipe, conforms to ASTM A500 GRADE B or Customized. 
  Helices material: ASTM A36 hot rolled plate. 
  Corrosion protection: ASTM A153, hot dipped zinc coating. 
  Leading edge of helices beveled 45 degrees. 
  Greater section modulus strength to resist twisting and deflection. 
  Greater load capacities.