Type W - steel, not hardened
Type H - steel, hardened
DIN1804 Slotted Locknut, Steel, Hardened or Unhardened
On these slotted lock nuts, DIN1804, the ground surface d3 stands proud and should be used as a mating surface.
Sizes M45x1,5 to M60x1,5 have 6 slots.
Type W - Steel ST, Tensile strength class 5.8 (500 N/mm2), not hardened, blackened.
Type H - Steel ST, Tensile strength class 5.8 (500 N/mm2), hardened HRC 60 ± 2 (thread not hardened). Mating surface ground or fine turned.
Compatible C spanners DIN1810 are also available.