When deciding on the material to be used and the surface roughness of the mating surfaces, the conditions under which the bearing system is to operate are of considerable importance.

In most cases, soft carbon steels with polished surfaces will be adequate. For demanding applications, hardened mating surfaces with a minimum surface hardness of 50 HRC or featuring a surface treatment by hard chrome plating, nickel plating etc. are of great advantage. In these cases, R_a should not exceed 0.3 µm (12 µin) and R_z should not exceed
2 µm (80 µin).

Improved surface finishes will improve the running characteristics; poor surface finishes will increase wear.

Roughness measuring units R_a and R_z in accordance to
DIN ISO 4288