### How to Identify Bearings by Bearing Number - Calculation

31/07/2018· The third and fourth digit of bearing patter number indicates the bore size of bearing. It is the inner diameter of the bearing and measured in millimeters. In general, the bore size is equal to five times the third and forth digit of bearing's patter number. However, from '0' to '3', this formula does not imply. The bore size indicated by '0' to '3' are : Fig. 4 – Bore