RHP7924CTDUMP4Super Precision Angular Contact Ball Bearing – 120 mm ID, 165 mm OD, 22 mm Width, Open, 15° Contact Angle, Phenolic Cage, Duplex Universal Medium Preload Pair

Product Description

What this part is

RHP 7924CTDUMP4 super precision angular contact ball bearing. Series: 7900, extra light section. ISO designation 71924. Bore: 120 mm. Outside Diameter: 165 mm. Width: 22 mm. Contact Angle: 15°. Single row, open, universally ground and matchable. Also written 7924-C-T-DUM-P4, 7924 C T DUM P4 and 71924CTDUMP4.

Decoding the designation

C: 15° contact angle. T: machined laminated phenolic cage, outer ring land riding, rated to 120 °C. DUM: duplex pair, universally ground, medium preload. P4: EP7, equivalent to ABEC 7. Carton cross designations 7924X2 and Fafnir 2MM9324WICRDUM carry the same 15° angle.

What these specs mean in practice

Basic Dynamic Load Rating: 90.5 kN per bearing. Basic Static Load Rating: 81.0 kN per bearing. Permissible Axial Load: 50.5 kN. The 7900 extra light section puts a large bore inside a small outside diameter, which is what a compact high speed spindle needs. A 15° contact angle favours speed and radial stiffness. Limiting speed runs to 8,100 rpm on grease and 12,300 rpm on oil or oil-air lubrication. The phenolic cage is light and self lubricating and holds ball guidance steady to 120 °C.

Preload and rigidity

Medium preload, 1,288 N across a back-to-back or face-to-face pair, giving 199 N/µm axial rigidity and 35 µm measured axial clearance. Effective Load Center a: 30.1 mm. Medium preload sits between the light setting’s low heat generation and the heavy setting’s stiffness, and it is the usual choice for a general purpose spindle position.

Quantity and configuration

Two bearings, supplied as a universally ground duplex pair at medium preload. Universally ground rings mount back-to-back, face-to-face or in tandem, with the preload set by the ground ring faces.

Fitting notes

Diameter of Shaft Abutment, da min: 127 mm. Diameter of Housing Abutment, Da max: 158 mm and Db max: 160 mm. Radius of Shaft or Housing Fillet, ra max: 1 mm, rb max: 0.6 mm. Bearing chamfer r min: 1.1 mm, r1 min: 0.6 mm. Recommended grease quantity: 7.3 g per bearing.

Interchange guidance

ISO base number 71924. Direct equivalents at the same 15° angle, P4 class and medium preload: NSK 7924CTRDUMP4, SKF 71924 CD/P4ADGB, FAG B71924-C-T-P4S-DUM, Fafnir 2MM9324WICRDUM.