Fafnir2MM210WICR-DUMSuper Precision Angular Contact Ball Bearing 50 x 90 x 20 mm, 15° Contact Angle, ABEC 7/9, Phenolic Cage, Medium Preload

Product Description

What this part is

One Fafnir (now Timken) 2MM210WICR super precision angular contact ball bearing, 50 mm bore × 90 mm outside diameter × 20 mm wide, with a phenolic cage and a 15° contact angle. It is from the 200 light series, the ISO 7210 envelope, ground to ABEC 7/9 and universally flush ground so it butts up against a second bearing to form a back-to-back, face-to-face or tandem set. Made in USA. This is a machine tool spindle bearing.

Designation breakdown

2: Timken code for a 15° contact angle, written C in ISO. MM: super precision, between ABEC 7 (ISO P4) and ABEC 9 (ISO P2), ISO equivalent code P4S. 210: 200 light series, bore code 10 (10 × 5 = 50 mm). WI: angular contact with a low shoulder on the outer ring only. CR: phenolic (composition) outer-land-riding cage, Timken’s standard for this family, written T in ISO. DUM: universally flush ground duplex bearings at medium preload. DU means the part was made and sold as a matched pair. M is the medium preload step between L (light) and H (heavy).

Specifications in practice

15° is the high-speed, lower-thrust option, giving the highest speed capability and the least axial stiffness of the standard angles. The 25° version (Timken 3MM, ISO E) trades speed for thrust capacity. Medium preload sits in the middle of the preload trade-off: more preload buys stiffness and running accuracy under load, and costs speed, friction and heat. At this size the published back-to-back speed drops from 12,500 rpm on grease at light preload to 9,600 rpm at medium and 6,400 rpm at heavy, while axial stiffness climbs from 64.19 to 95.67 to 139.57 N/µm. The phenolic cage is light, runs quiet, holds oil in the resin, and tolerates momentary lubrication starvation better than a steel cage. Its ceiling is near 93 °C (200 °F), above which machined bronze is the usual substitute.

Published ratings

Figures from the Timken Fafnir Super Precision Bearings for Machine Tool Applications catalogue (order 5918), 15° steel-ball columns. Basic dynamic radial load rating C: 47,400 N (10,700 lbf). Basic static radial load rating C0: 31,700 N (7,130 lbf). Speed rating (Ng): 16,000 rpm for a single grease-lubricated spring-preloaded bearing. Ball complement: 14 steel balls, 12.70 mm (1/2 in) diameter. Bearing weight: 0.457 kg (1.01 lb). Preload as a matched pair: DUM 560 N (125 lbf), DUX 130 N, DUL 220 N. Back-to-back speed at medium preload: 9,600 rpm grease, 16,300 rpm oil. Stiffness at medium preload: 95.67 N/µm axial, 496.89 N/µm radial. The preload and paired-speed figures are published for a pair.

Mounting data

Maximum shaft fillet radius: 1.0 mm. Suggested shaft shoulder diameter: 57.9 / 57.4 mm. Suggested housing shoulder diameter: 83.3 / 82.8 mm. Grease fill: 2.15 g (10 %) to 3.20 g (15 %) at high speed, 4.80 g (25 %) to 7.60 g (40 %) at low to moderate speed. The outer ring is etched THRUST on one face. The WI construction has a low shoulder on the outer ring only, so the bearing carries thrust in one direction. The ring also carries 01P USA LOT #15707, a factory lot reference. The bearing is sealed in its original factory poly bag, with no carton.

Interchange guidance

The 50 × 90 × 20 mm, 15°, phenolic-cage, ABEC 7/9 combination is ISO 7210C-T-P4S. Timken’s own catalogue prints the pairing as 2MM210WICR / 7210C-T-P4/P4S. Same-envelope super precision bearings from other makers include NSK 7210CTRDUMP4, FAG B7210C.T.P4S.UM, SKF 7210 CD/P4A and NTN 7210CT1GD2GLP4. Preload class and cage are matched to the application, and none of these is a Timken-published interchange. Fafnir is a retired brand name: Fafnir super precision became Timken super precision, and the current-production part is ordered as a Timken 2MM210WICRDUM.