Semi-Precision Balls

Abbott’s 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 both ABMA and ISO 3290 standards, which dictate the specific parameters associated with the grade of 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.


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).


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).