Finding the size of a ball bearing in need of replacement, before purchase a new one, may save money. You also will have the correct replacement part the first time and avoid a return trip to the store. Determine ball bearing size by making a few measurements in millimeters. Ball bearings allow objects to move or rotate freely. Each disk shaped bearing contains a number of balls that roll. (See Reference 1) Ball bearings are used in industrial equipment as well as many types of wheels.
Measure the total diameter of the ball bearing in millimeters, as viewed from its circular side. Diameter measure the width of a circle along a line that passes through its center. (See Reference 2)
Determine the diameter, in millimeters, of the central hole in the bearing. This will ensure the replacement bearing fits onto its shaft.
Measure the thickness of the bearing as viewed from its edge in millimeters. You now have all relevant dimensions of the ball bearing.