RHP7211CTDUMP2Super Precision Angular Contact Ball Bearing Matched Pair – Straight Bore, 55 mm ID, 100 mm OD, 21 mm Width, Open, 15° Contact Angle, Medium Preload, ABEC 9

Product Description

What this part is

RHP 7211CTDUMP2 matched pair of single-row super-precision angular contact ball bearings, made in England. Bore: 55 mm. Outside Diameter: 100 mm. Overall Width: 21 mm. Contact Angle: 15°. Precision Class: P2, equivalent to ABEC 9, to BS292 EP9 and to ISO 492 Class 2. Number Of Rows: 1 per bearing. Rolling Elements: Balls. Bearing Material: Carbon chrome bearing steel to BS970 534A99/535A99, equivalent to SAE 52100, through hardened. Series: 7200, ISO dimension series 02. RHP is an NSK brand.

Decoding the designation

Reading 7211-C-T-DUM-P2: 7 is a single-row angular contact ball bearing, 2 is ISO dimension series 02, the bore code 11 gives a 55 mm bore, C is the 15° contact angle, T is the laminated phenolic resin cage, DU marks a paired unit, M is medium preload and P2 is the precision grade. The carton also carries the Fafnir cross 2MMV211WI CR DUM, where 2MM is 15° and CR the phenolic outer-land-riding cage.

What these specs mean in practice

Dynamic Load Rating: 53.0 kN per bearing. Static Load Rating: 40.0 kN per bearing. Limiting Speed, oil-air lubrication: 23,000 rpm. Limiting Speed, grease lubrication: 14,200 rpm. Those figures are for a single bearing under light spring preload. Mounted as a back-to-back medium-preload pair the limiting speeds are multiplied by 0.60, giving 13,800 rpm on oil-air and 8,520 rpm on grease.

What the P2 accuracy class buys

Precision Class: P2, the tightest grade RHP builds in this range. Radial Runout Of The Assembled Inner Ring: 2.5 µm. Reference Face Runout With Bore: 1.3 µm. Radial Runout Of The Assembled Outer Ring: 3.8 µm. Deviation Of Mean Bore Diameter: 0 to −3.8 µm. P2 sits a full grade above the P4 that covers most spindle work, and buys lower runout, closer shaft location and quieter running at speed.

Cage and temperature

Cage Material: Laminated phenolic resin. Cage Type: Outer-ring guided. Maximum Operating Temperature: 120 °C, the limit set by the phenolic cage.

Preload and stiffness

Preload: Medium. Axial Preload: 780 N for the mounted pair. Axial Stiffness: 117 N/µm. RHP publishes exactly four preload grades: extra light, light, medium and heavy. Medium buys rigidity and positional accuracy at the cost of speed capability.

Mounting data

Bore Type: Straight. Closure Type: Open. Minimum Shaft Abutment Diameter: 64 mm. Maximum Housing Abutment Diameter: 91 mm. Maximum Outer Ring Abutment Diameter: 94 mm. Chamfer r min: 1.5 mm. Chamfer r1 min: 1.0 mm. Effective Load Centre a: 20.9 mm. Internal Volume: 27.8 cm³. Pitch Circle Diameter Of Lubrication Jets: 72.0 mm. The rings are universally faced, so the pair mounts back-to-back or face-to-face without altering the preload value.

Quantity and configuration

Unit Quantity: 2 Pcs. Arrangement: DU, a universally matched pair. Item Weight: 1.206 kg (2.66 lb) for the pair, 0.603 kg (1.33 lb) each.

Interchange guidance

Cross-references with the same 15° angle and medium preload: FAG B7211-C-T-P2S-UM, Fafnir 2MMV211WI CR DUM and SKF 7211 CDGC/P2. The designation is also written 7211CTDUMP2, 7211 C T DUM P2 and 7211-C-T-DUM-P2. A 7211 at a 25° contact angle shares this 55 x 100 x 21 mm size but carries different ratings and speeds, so it is a related size rather than a substitution.