RHPSuper-Precision Angular Contact Ball Bearing – Thin Section, Straight Bore, 90 mm ID, 125 mm OD, 18 mm Width, Open, 15° Contact Angle, Light Preload, Universally Matchable Single, 1 Pc.

Product Description

What this part is: An RHP 7918CTSULP4 super-precision angular contact ball bearing, a single universally matchable bearing set to light preload. Bore 90 mm, outside diameter 125 mm, width 18 mm. One row of balls, open on both faces, running in a fabric-base phenolic laminate cage guided on the outer ring land. In ISO terms this is a 71918C, a thin-section design in the 719 dimension series. RHP is the British super-precision line now part of NSK. Decoding the designation: The carton carries four designations for the same bearing, and each one independently confirms the 15° contact angle. In the RHP scheme 7918-C-T-SUL-P4 reads: C is 15°, T is the phenolic laminate cage, SU is single and universally ground, L is light preload, P4 is precision class ABEC 7. The ISO number 71918C carries the same C. The RHP B-series number 7918X2 uses X2 for 15°, where X3 would be 25°. The Timken/Fafnir number 2MM9318WI CR SUL uses 2MM for 15°, where 3MM would be 25°, and CR for the outer-land-riding phenolic cage; the 9300WI series maps to the ISO 719xx family, so 9318 is a 71918. What these specs mean in practice: A 15° contact angle directs load closer to the radial plane, which favours speed and radial stiffness; a 25° bearing on the same envelope carries more thrust and runs slower. The 719 series is a thin section, so it fits a large bore into a small outside diameter and a narrow width, which is why it suits compact spindle noses and rotary tables where radial space is short. Light preload holds running accuracy and prevents ball skidding while keeping friction and heat low. The phenolic laminate cage is light, self-lubricating and quiet at speed. Load ratings on this envelope: The static rating exceeds the dynamic rating on this bearing, at 41.5 kN static against 39.0 kN dynamic. That is normal for a thin-section 719-series bearing, which carries a large number of small balls: the many contact points raise permissible static load while the small ball diameter limits dynamic capacity. SKF publishes the same relationship on its 71918 on this envelope. Quantity and configuration: One bearing. Universal grinding of the ring faces means it can be paired with another bearing of the same designation in a back-to-back, face-to-face or tandem set, with the ground offsets producing the specified light preload once the rings are clamped solid. Used alone it runs as a single-row angular contact bearing taking thrust in one direction. Because the bearing is preloaded when matched rather than clearance-set, radial internal clearance does not apply. Fitting notes: Thrust is carried in one direction only, so the bearing locates axially against a shoulder or an opposing bearing. Preload in a matched set is established by clamping the ground ring faces solid; no shim stack or spacer is required. Shaft and housing seats held to ISO 4 or better preserve the running accuracy the P4 class buys. Grease fill for a preloaded phenolic-caged spindle bearing is typically 15 to 20 percent of free space. Interchange guidance: Same-specification 15° light-preload bearings on this envelope include the SKF 71918 CDGA/P4A and the FAG B71918-C-T-P4S-UL. The SKF 71918 ACD/P4A and the Fafnir 3MM9318WI share the 90 x 125 x 18 mm envelope at a 25° contact angle, which makes them a related size rather than a substitution. A 7918CTRDULP4 is the duplex-pair version of this designation.