Precision balls are used in critical aeronautical bearings, guidance system balls for space and military applications, precision valves, automotive bearings and other applications where higher precision is necessary. Precision balls are defined by grade: The lower the number of the grade, the more precision to which the ball is manufactured. The typical distinction between a precision ball and a semi-precision ball is between grades 50 and 100, wherein the grade 50 is considered a precision ball and the grade 100 is not. This definition arbitrarily varies by company. Abbott precision balls are available in grades 3 to grade 50, lap finished 300 series, 440C, 440CVM, 52100 Chrome, vacuum melt chrome balls and soft stainless steel grade 25 balls. Abbott conforms to ABMA standards, which dictate the specific parameters associated with the grade of a ball.
Sphericity - the better the grade of ball the closer to a perfect sphere a ball is made. Sphericity of a ball is critical for valve applications where the liquid passed through the valve requires tighter application to the tube, or nozzle. The normal range of sphericity for precision balls is from grade 3 at ±0.000003 to grade 50 ±0.00005.
Surface Integrity or Tribology of a ball is critical to the surface-to-surface and/or surface-to-lubricant circumstances. Precision balls are required to have a better surface finish to ensure that the coefficient of wear is such that the ball has limited surface defects effecting the rotation of the ball as it passes through the bearing or other application. The better the surface finish, the less "noise" from vibration during bearing rotation. Surface finish can also be critical to providing a tight valve seal.
Diameter - the better the grade of ball, the tighter the ball diameter tolerance: For example, an eighth-inch grade 3 ball has a diameter tolerance of ±0.00003, whereas an eighth-inch grade 200 semi-precision ball has a diameter tolerance of ±0.001. Diameter is critical for quiet bearings.