Ball Grade Chart
| Grade | Sphericity | Basic Diameter Tolerance |
|---|---|---|
| 3 | .000003″ | +/- .00003″ |
| 5 | .000005″ | +/- .00005″ |
| 10 | .000010″ | +/- .0001″ |
| 25 | .000025″ | +/- .0001″ |
| 50 | .000050″ | +/- .0002″ |
| 100 | .0001″ | +/- .0005″ |
| 200 | .0002″ | +/- .0010″ |
| 500 | .0005″ | +/- .002″ |
| 1000 | .001″ | +/-.005″ |
GRADE
The guaranteed sphericity expressed in millionths of an inch. For example, a grade 25 ball is spherically accurate within 25 millionths of an inch.
SPHERICITY
The difference between the largest diameter and the smallest diameter on a single ball.
BASIC DIAMETER TOLERANCE
The maximum allowable deviation from the basic diameter.