USA Thin Section Bearing manufacturer Silverthin Precision Bearings part of Mechatronics Inc provides an insight into the effect of Precision Class in Thin Section Bearings.
What are ABEC / ISO and DIN grades?
ABEC stands for Annular Bearing Engineering Committee. ABEC is part of the American Bearing Manufacturers Association, which acts as the official governing body of the bearing industry in the United States. The bearing grades and tolerance specifications come in five classifications; 1, 3, 5, 7, and 9. European bearing precision classes are normally categorised under the ISO or DIN standards and follow a similar format to the American ABEC classes. Normal / P0, Class 6 / P6, Class 5 / P5, Class 4 / P4 and Class 2 / P2.
As the ABEC grades increase the tolerances tighten from least to the most precise. The ISO and Din systems work in reverse so that the tolerances tighten from most precise to least. The grades control tolerances from boundary dimensions such as bore and OD, to tolerances like axial run-out that impact rotating accuracy, and values like the dimension measured from the centre point of the raceway to the side faces of the bearing.
Classification does not govern all aspects of bearing quality. There are many critical design features of bearings that are not covered by classification classes, including: material, cage, retainer type, surface finish (smoothness) of the rolling elements and raceways, clearance, preload, ball precision grade, or anything to do with the ancillary components like seals, snap rings and lubricants. Classification also does not directly control noise level or torque. Precision classification classes also apply to specialist Thin Section Bearings.
The table below provides a useful reference to help interchange between the various classification systems. The exact tolerance bands are not identical but they offer a very good reference point.
|ABEC SYSTEM||ISO SYSTEM||DIN SYSTEM|
|ABEC 3||Class 6||P6|
|ABEC 5||Class 5||P5|
|ABEC 7||Class 4||P4|
|ABEC 9||Class 2||P2|
Why aren’t all bearings made to ABEC 9, Class 2 or P2?
As with most things in the manufacturing world, higher precision means higher cost, and the term “precision” is relative – one designer’s need for “precision” may actually require the higher end of the precision class and another may be satisfied with the lower end. There are also many cases where a problem with a bearing system cannot be solved simply by increasing the level of precision.
Deciding on a precision class boils down to a cost / benefit decision for the designer. A bearing made to mid-range P5 will have tolerances that are approximately half those of a P0 bearing, but it could cost two or three times as much.
Which precision class should I design into my application?
The grade specified for an application depends on the type of equipment and its function.
A mechanical inspection system for a silicon platter may require a reader head located very close to the surface of the wafer. It is critical to control the movement of the inspection system in the horizontal axis, which has direct correlation to the axial run-out of the bearing in the system. A bearing of at least ABEC-5 / Class 5 or P5 grade would be required to provide the necessary precision in this application.
A gun mount would require far less dimensional control or rotational accuracy. Preloading will impact the bearing’s performance far more as the bearing experiences heavy shock loads and external forces. Tolerances like axial run-out will have less impact on the accuracy of the system than the movements of the operator. Bearings in this application should be preloaded to increase system stiffness, but tolerances would be sufficient at an ABEC-1 / Normal / P0 level.
To determine the best precision classes for your design, why not Click Here to view the available options from the Silverthin product selector or alternately contact us to discuss your application with a Carter Bearings engineer.
A turntable is an application where higher rotating accuracy may not be critical, but the assembly steps of the unit are very important to the function of the system as a whole. Using an ABEC-5 / Class 5 or P5 bearing will result in consistent fit with the shaft, helping standardize the mounting forces and installation time for every assembly. A hybrid that has an ABEC-5 / Class 5 or P5 bore tolerance and ABEC-1 / Normal / P0 class for all other tolerances will prove to be cost effective and meet the requirements of the application. Silverthin is able to provide a flexible solution producing a hybrid bearing that only has tighter control of the specifically required dimension at a much lower cost point.
Turning “Revolutionary Ideas into Motion”
Carter Manufacturing Limited is the Silverthin European Master Distributor. The partnership between Carter and Silverthin allow flexibility and capacity to customize products to meet customers challenging and often demanding requirements with accuracy, value, and performance. The Silverthin product catalogue options are only the beginning of what can be provided for diverse applications.
From standard thin section bearings and high precision specials, to hybrid combinations of both precise and cost effective components.
Why not let Carter Manufacturing Limited help you specify the most appropriate thin section bearing for your application and then let Silverthin customize your bearing product to your requirements of accuracy, optimal value, and performance.
Precision Thin Section Bearings in the standard Silverthin catalogue are only the beginning of what we can provide for diverse solutions.
Contact Carter today to get a helping hand in turning your revolutionary ideas into motion. Tel: +44 (0)1865 821 720
Author: Martin Wakelin, Carter Manufacturing Limited