1. Nominal ball diameter: it’s generally used to identify the diameter of the ball.
Note: nominal ball diameter is each nominal size of steel balls’ diameter(standard diameter), which can be repaired by the 4 decimal point.
2. Single ball diameter: the distance between the two parallel planes that are tangent to the actual surface of the steel ball.
3. Mean ball diameter: the arithmetic mean of the maximum and minimal single diameter of the steel ball.
4. Variation of ball diameter: the difference between the maximum and minimal single diameter of the ball.
5. Deviation from spherical form: all kinds of deviations from the surface of the ideal steel ball, which are evenly distributed or unevenly distributed and emerge repeatedly across the entire spherical form.
Note: these deviations are caused by:
-- deviation from spherical form;
-- surface roughness;
-- surface defect.