RHP7918CTDUMP4Angular Contact Ball Bearing Matched Pair – Straight Bore, 90 mm ID, 125 mm OD, 18 mm Width, Open, 15° Contact Angle, Medium Preload

Product Description

What this part is

RHP 7918CTDUMP4 super precision angular contact ball bearings, supplied as a matched duplex pair. Series: 7900, ISO dimension series 19. Bore: 90 mm. Outside diameter: 125 mm. Width: 18 mm each bearing, 36 mm assembled. Straight bore, open on both faces, ball rolling elements in chrome bearing steel to SAE 52100. Country of origin as recorded: United Kingdom.

Decoding the designation

Contact Angle: 15°. Cage: laminated phenolic resin, machined and outer-ring guided. Grouping: DU, paired unit. Preload: M, medium. Precision Grade: P4, equal to RHP EP7 and ABEC 7. Searchable forms include 7918CTDUMP4, 7918-C-T-DUM-P4, 7918 C T DUM P4, the ISO form 71918C, the RHP B-series form 7918X2 and the Fafnir cross 2MM9318WICR-DUM.

What these specs mean in practice

Dynamic Load Rating: 41.5 kN per bearing. Static Load Rating: 46.0 kN per bearing. Limiting speed for a single bearing: 9,500 rpm with grease, 15,400 rpm with oil/air. As a medium-preload back-to-back pair those figures carry a 0.60 factor, giving 5,700 rpm and 9,240 rpm. A 15° contact angle runs faster and carries less thrust than a 25° bearing on the same envelope, which is why it is the usual choice on high-speed spindles. Medium preload raises stiffness to 156 N/µm at 740 N of axial preload. The ISO 19 section is the thinnest of the three super precision series, so this bearing fits a large shaft in a small housing envelope.

Quantity and configuration

Two bearings, a matched duplex pair. Universal face control means they mount back-to-back, face-to-face or in tandem at the same medium preload, set at manufacture. The high point of radial runout is marked with a burnished spot on the inner ring face and a V line on the outer diameter.

Fitting notes

Abutment diameters from the RHP super precision tables: shaft shoulder d1 minimum 97 mm, housing shoulder D1 maximum 118 mm, D2 maximum 120 mm. Fillet radius r minimum 1.5 mm, r1 minimum 0.6 mm. Effective load centre a = 23.4 mm. Internal free volume 25.6 cm³ per bearing. Lubrication jet pitch circle 102.8 mm. Mass 0.559 kg per bearing, 1.118 kg for the pair.

Interchange guidance

Same-specification equivalents at 15° and medium preload: SKF 71918 CD/P4ADGB, Fafnir 2MM9318WICR-DUM, NSK 7918CTRDUMP4, FAG B71918-C-T-P4S-UM. RHP 7918A5TDUMP4 is a related size at 25°.