Steel balls are the basic elements of ball bearings. They are made from through hardened rolling bearing steel in accordance with DIN 17 230 and have a hardness of at least 740 HV10. The dimensions and tolerances conform to DIN 5 401/ISO 3 290.

The balls are available in the grades G5, G10, G16, G20, G28, G40. The largest and smallest deviation and the geometrical tolerance are defined as a function of the diameter. The suffixes correspond to the class designations.

Balls manufactured under identical conditions (batches) are sorted within a class into ball sorts with a very small diameter tolerance according to the mean batch diameter D_wmL.

Each sort is packed separately and the mean deviation is marked on the packaging.

One pack contains balls of one sort only.

In a delivery of balls of the same nominal dimension and class comprising several packs, the sort may differ from one pack to another.

Preferred sort range in grades G10 to G40: +6 to –6.

The sort designation is printed on the packaging:

• N for zero
• P for a positive value (stating the value)
• M for a negative value (stating the value).

Balls of only one sort should be used in one bearing arrangement.

The mass in the dimension tables is calculated on the basis of ρ = 7,85 kg/dm³ (DIN 5 401).

Balls are available by agreement in other sizes and made from other materials, such as special steels and ceramic.

Balls are used:

• in rolling bearings where moderate to high speeds occur and moderate to high axial forces and radial forces must be supported, for example in deep groove ball bearings, slewing rings, rotor bearings and linear guidance systems
• in the automotive industry, in machine building, in the electrical, DIY and household appliances industries as well as in toys and games
• in constant velocity joints and as valve balls.

Suffixes for available grades: see table.