RHP7203CTDUMP4Super Precision Angular Contact Ball Bearing 17x40x12 mm, 15 Degree Contact Angle, Phenolic Cage, Duplex Universal Medium Preload

Product Description

What this part is

A super-precision angular contact ball bearing in the 72-series, 17 mm bore × 40 mm outside diameter × 12 mm width, ground to duplex universal standard at medium preload with a 15° contact angle. A small machine tool spindle bearing, typical of grinding spindles, high-frequency spindles and precision instrument drives.

Decoding the designation

7203 — ISO 72-series angular contact, 17 × 40 × 12 mm.
C — 15° contact angle.
T — machined laminated phenolic cage, outer-ring guided.
DUM — duplex universal ground, medium preload. Universal grinding means the two bearings can be stacked back-to-back, face-to-face or in tandem and the specified preload is produced by simply clamping them together, with no shims or measurement.
P4 — ISO tolerance class 4, equivalent to ABEC 7.

What these specs mean in practice

A 15° contact angle biases the bearing toward radial load and speed rather than thrust. It runs cooler than a steeper-angle bearing at the same rpm, holds radial running accuracy better, and reaches a higher limiting speed — which is exactly why grinding and high-frequency spindles specify it. The trade is axial capacity and axial stiffness, so a 15° set is the wrong choice for a drilling or boring spindle carrying heavy one-way thrust.

Medium preload raises stiffness and positional accuracy above a light-preload set, at the cost of some heat and speed headroom. Because the preload is ground into the ring faces it cannot be adjusted during assembly — specifying the class correctly at purchase is the whole decision.

Published ratings and mounting data

Manufacturer-published single-bearing figures for the 7203C super-precision bearing at 15°:

Dynamic load rating Cr — 13.7 kN
Static load rating Cor — 5.85 kN
Limiting speed — 40,000 rpm grease, 50,000 rpm oil-air

Ball count and ball diameter are not published for this designation. The catalogued speeds are quoted against the polyamide-cage version of the C-type bearing; a machined phenolic cage is a different thermal case, so treat them as indicative for the envelope rather than certified for this cage variant.

Quantity and configuration

DUM describes a matched pair. Surplus duplex stock is regularly split, so no pair-count claim is published on this listing — confirm the piece count against your requirement before ordering. Where multiple pieces are held, only bearings ground as one original set will produce the specified preload when clamped together; two unrelated halves will not.

Fitting notes

Keep matched rings together and align the etched face markings as ground. Observe thrust direction — a single angular contact bearing carries thrust one way only, and reversing it leaves the bearing effectively unloaded under working load. Bearings ship coated with preservative rather than charged with service lubricant; degrease and apply the spindle grease or oil-air feed your machine specifies.

Interchange guidance

The RHP legacy form of this bearing is 7203X2TADUMEP5-family nomenclature, in which X2 confirms the 15° angle and TA denotes the one-piece outer-ring-centred phenolic cage. World-number format is 7203C-T-P4S-DUM; Schaeffler format is B7203-C-T-P4S-DUM. The Fafnir 15° equivalent envelope is the 2MM203WI family. RHP super-precision production passed to NSK, which remains the source for a new-build equivalent.