JIS standard for steel balls
Rolling bearings - Balls JIS B 1501 excerpt
Terms and definitions
- Single ball diameter, Dws
- The distance between two parallel planes tangential to the actual surface of a ball.
- Deviation from spherical form
- The radial distance between the smallest circumscribed sphere and the greatest inscribed sphere, with their centers common to the least squares sphere centre.
- Ball lot
- A definite quantity of balls manufactured under conditions presumed uniform and which is considered as an entity.
- Ball grade （G）
- A specific combination of dimensions, form, surface roughness and sorting tolerances. Ball grade is indentified by the letter G and a number.
Measuring methods
- Mean diameter of a ball and ball diameter variation
- The diameter necessary for determining the mean diameter of a ball and the ball diameter variation shall be measured with the ball placed between the horizontal plane and the stylus applied vertical to it from different directions.
- Deviation from spherical form
- The method of evaluating the deviation from spherical form of a steel ball shall be in accordance with JIS B 1501 appendix A.
- Surface roughness
- "For the surface roughness, measure the roughness around the equators of the steel ball with the instrument specified in JIS B 0651, as a rule, and take the center line mean roughness."
Unit：1μm＝1/1000mm
| Grade (Ｇ) |
Applicable range of ball size (mm) |
Ball diameter variation (μm) |
Sphericity (μm) |
Surface roughness Ra (μm) |
Lot diameter variation (μm) |
|---|---|---|---|---|---|
| 3 | 0.3～12 | 0.08 | 0.08 | 0.010 | 0.13 |
| 5 | 0.3～12 | 0.13 | 0.13 | 0.140 | 0.25 |
| 10 | 0.3～25 | 0.25 | 0.25 | 0.020 | 0.5 |
| 16 | 0.3～25 | 0.4 | 0.4 | 0.025 | 0.8 |
| 20 | 0.3～38 | 0.5 | 0.5 | 0.032 | 1 |
| 24 | 0.3～38 | 0.6 | 0.6 | 0.040 | 1.2 |
| 28 | 0.3～38 | 0.7 | 0.7 | 0.050 | 1.4 |
| 40 | 0.3～50 | 1 | 1 | 0.060 | 2 |
| 60 | 0.3～65 | 1.5 | 1.5 | 0.080 | 3 |
| 100 | 0.3～65 | 2.5 | 2.5 | 0.100 | 5 |
| 200 | 0.3～65 | 5 | 5 | 0.150 | 10 |