Abbott semi-precision balls are used in a wide variety of applications where the higher tolerances and cost of precision balls is not necessary. 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 grades 50 and below are considered precision balls and grades 100 and above are semi-precision. Abbott conforms to ABMA standards, which dictate the specific parameters associated with the grade of a ball.
Surface Integrity is defined as the surface smoothness and freedom from defects such as flats, pits, soft spots and cuts. Semi-precision balls must be free of such defects when inspected without magnification.
Size is the mean diameter, measured between two parallel planes on the ball surface. Tolerances for semi-precision balls are ±0.0005 (grade 100) up to ±0.005 (grade 1000).
Sphericity is defined as the deviation (out-of-round condition) from a true spherical form. The normal range of sphericity for semi-precision balls is between ±0.0001 (grade 100) and ±0.001 (grade 1000).