ABEC ratings have to do with the quality and precision of the bearing. It is an industry accepted standard developed by the Annular Bearing Engineering Committee (ABEC) of the American Bearing Manufacturers Association (ABMA). There are five (5) ABEC classifications 1, 3, 5, 7, and 9; the higher the number, the more precise the bearing.
ABEC 7 bearings are also referred to as “Super Precision Bearings” and are equivalent to ISO P4. These bearings are specifically designed for machine tool applications. Typically they are purchased in matched sets or quad sets. HST always uses ABEC 7 or ABEC 9 (Super High Precision, ISO P2) bearings.
Amongst other factors ABEC classifications relate to the eccentricity of the bearing.
- ABEC 1: 0.0075 mm (0.000295″)
- ABEC 3: 0.0050 mm (0.000197″)
- ABEC 5: 0.0035 mm (0.000138″)
- ABEC 7: 0.0025 mm (0.000098″)
- ABEC 9: 0.0012 mm (0.000047″)
When assembling Super Precision Bearings the manufacturer matches the balls to the races using a very tight tolerance. Although assembled on high speed equipment each Super Precision Bearing is a “custom” assembly. Each race is individually measured to better than 1 µm and then assembled with balls that exactly match the race variation. That is just one of the factors that influence the price of the ABEC 7 bearings. It is not uncommon for bearings in a medium size spindle to cost over $2000.
In the past HST only used matched set bearings. These are bearings that are ground together in the same operation. There is a move in the industry to use P4Y or equivalent bearings. These bearing are universally ground to very tight tolerances. In theory, deviation from any individual bearing to any other bearing is within the tolerance for a matched set. Prior to assembly our technicians test each bearing set to verify proper loading. Our technicians have had several P4Y bearings sets that have not passed their scrutiny. Our bearing suppliers complain that we reject more bearings than all their other customers combined. Well, the customer sees our name on the repair not the bearing manufacturer. None the less, manufacturing processes continue to improve and we believe that matched sets will be phased out in favor of P4Y bearings or similar designation. In any event, HST will continue to test and inspect every set of bearings that we receive to make sure they are within our tolerance. We will only use the finest components available.