RHPSuper Precision Angular Contact Ball Bearing Duplex Pair – 140 mm ID, 210 mm OD, 33 mm Width, 25° Contact Angle, P4, Light Preload, Open

Product Description

What this part is

RHP 7028ETDULP4 super precision angular contact ball bearings, supplied as a factory matched duplex pair. Bore: 140 mm (5.512 in). Outside diameter: 210 mm (8.268 in). Width: 33 mm (1.299 in) per bearing, 66 mm across the pair. Series: 70, ISO dimension series 10. Single row each, open, straight bore, universally faced. Manufactured in the United Kingdom.

Decoding the designation

Contact Angle: 25°. Cage: machined laminated phenolic resin, outer ring guided. Grouping: DU, paired unit. Preload: Light. Precision Grade: P4, equivalent to EP7, ABEC 7 and ISO Class 4.

What these specs mean in practice

Dynamic Load Rating: 125 kN per bearing. Static Load Rating: 138 kN per bearing. Limiting speed: 8,400 rpm on oil/air lubrication and 5,500 rpm on grease for a single bearing. A 25° contact angle carries more thrust and less speed than a 15°, which suits spindles with a heavy axial component. P4 holds tighter running accuracy, which lowers runout and vibration: inner ring radial runout 5 µm maximum, outer ring radial runout 10 µm maximum.

Preload and stiffness

Axial preload for this light-preload pair: 1,570 N. Axial stiffness at light preload: 413 N/µm. Mounted back-to-back, the recommended limiting speed for a light-preload pair is 0.80 of the single-bearing figure, giving 6,720 rpm on oil/air and 4,400 rpm on grease. Preload is set at manufacture, so no internal clearance value applies.

Quantity and configuration

Two pieces, a factory matched duplex pair. Universal face control means the rings are pre-adjusted, so the pair mounts back-to-back, face-to-face or in tandem at the marked light preload without ground spacers.

Mounting data

Inner ring abutment diameter d1: 150 mm minimum. Outer ring abutment diameters D1 and D2: 200 mm and 204 mm maximum. Fillet radii r and r1: 2.5 mm and 1.0 mm minimum. Effective load centre a: 57.3 mm. Lubrication jet pitch circle diameter: 165.7 mm. Internal free volume: 141.0 cm3 per bearing. Maximum recommended operating temperature: 120 °C. Rings and balls: SAE 52100 through-hardened chrome bearing steel. Mass: 3.414 kg (7.53 lb) each, 6.828 kg (15.05 lb) for the pair.

Interchange guidance

Carton designations: 7028ETDULP4, 7028-E-T-DUL-P4, B-7028-X3-T-UL-EP7, 3MM9128WICRDUL. Fafnir 3MM9128WICRDUL is the 25° light-preload duplex equivalent. NSK 7028A5TRDULP4 is the current-scheme equivalent at 25° with the same outer-ring-guided phenolic cage. SKF 7028 ACD/P4ADGA is a 25° light-preload equivalent.