What are the big differences in measuring small diameter balls?

On balls of approximately one quarter inch ( ¼", 0.25", 8mm ) diameter and larger, the ball diameter is measured on three precisely orthogonal ( 90 degree ) diameters and the measurements are arithmetically averaged by a computer automatically. Small balls do not lend themselves to the normal orthogonal diameter measurement procedure. The small diameter of these balls simply precludes the accurate orthogonal indexing of a single ball.

On smaller diameter balls, multiple random measurements of single balls can be made or a single measurement of multiple balls can be performed. Either of these methods will yield equally good results. To minimize any possible human errors in the diameter measurement of balls, we have written computer software that interfaces with the Heidenhain laser scale measuring equipment that we use to measure all but the very large diameter balls. The mathematical algorithm used in this software arithmetically averages three individual ball measurements and prints out the results.

This procedure is repeated at least three times and the data is stored with reference to the original work order number. If the final data does not correspond to the customer purchase order specifications, no shipping documents or mailing labels will be printed by the computer, so an out of tolerance order simply can not be shipped. When the diameter of a ball is measured, by physically contacting it with the surfaces of the gaging device, there will be hertzine elastic deformations that must be compensated for. As a general principal the smaller the ball diameter the greater the elastic deformation will be.