The miniature and instrument bearing normally takes the form of a deep groove ball bearing with a bore below 10mm. Miniature bearings ironically carry the largest sizes as the following features are normally specified:

• Shielding or sealing options
• Cage or retainer type
• Precision
• Radial Clearance
• Lubrication type (and sometimes quantity)

Typical miniature aerospace bearing manufacturers include NHBB/NMB, RMB. GRW, WIB, Barden and Timken (MPB). All of these manufacturers have their own means of identifying bearing sizes and their features but most of them follow a general pattern that can quickly be identified.

Miniature and instrument bearings usually have exacting tolerance, radial clearance and lubrication requirements. These requirements should never be deviated from as even the smallest changes in bearing specification can yield differing results with instrumentation.

AHR has a vast range of interchanges against many OE miniature-bearing references including interchanges against Bendix, AIM, Collins, Lear Siegler, Electric Gyro, Aireitalia and Air Search.