Fafnir3MM307WIDUHSuper Precision Spindle Angular Contact Ball Bearing 35x80x21 mm, 25 Degree Contact Angle, Phenolic Outer-Land-Riding Cage, Duplex Universal Heavy Preload, ISO P4S

Product Description

What this part is

Fafnir 3MM307WICRDUH super-precision spindle angular contact ball bearing. 35 mm bore, 80 mm outside diameter, 21 mm width. Contact Angle: 25 degrees. Precision Class: ISO P4S (running accuracy to ABEC 9 / ISO P2). Cage Material: Phenolic composition, outer-ring-land riding, rated to 93°C. This is the heavy-section 73-series, carrying more load than a 70- or 72-series bearing of the same bore. Mounted as a duplex pair the set occupies 42 mm of shaft length.

Decoding the designation

3MM denotes the 25 degree super-precision spindle series; 2MM is the 15 degree series. 307 is the 73-series bore code for 35 mm bore in the 80 mm outside-diameter envelope. WI is angular contact geometry with full inner-ring shoulders and a low outer-ring shoulder, non-separable, carrying thrust one direction. CR is the composition (phenolic) cage riding on the outer-ring land. DUH is a flush-ground duplex pair at heavy preload; the series runs DUX extra-light, DUL light, DUM medium, DUH heavy.

What heavy preload means in practice

Heavy preload gives the greatest axial and radial stiffness of the four duplex classes and the tightest positional accuracy under varying load, which suits a rigid boring or heavy milling spindle. The mounted-pair speed at heavy preload runs at roughly 40 percent of the single-bearing figure, and the bearing generates more heat than a lighter preload class. Preload class is ground into the bearing and is fixed at manufacture.

Published ratings and mounting data

Dynamic Load Rating: 44,500 N (10,000 lbf). Static Load Rating: 24,700 N (5,600 lbf). Rolling Elements: 10 steel balls, 14.29 mm diameter. Preload Force (DUH): 1,560 N. Limiting Speed: 17,300 rpm single bearing; DUH pair mounted back-to-back, 6,930 rpm grease, 11,790 rpm oil. Assembled pair width: 42 mm.

Quantity and configuration

DUH designates a matched pair ground as a set. Unit Quantity: 2 Pcs, one flush-ground duplex pair. Bearings from a common original set reproduce the specified 1,560 N preload when clamped together. Mounting Arrangement: universal, mountable back-to-back, face-to-face or in tandem.

Interchange guidance

ISO world number: 7307E-T-P4S-DUH. Schaeffler format: B7307-E-T-P4S-DUH. The 15 degree sibling 2MM307WI CR DUH shares the 35 x 80 x 21 mm envelope and carries its own contact angle and load ratings. Fafnir spindle bearings are now branded Timken.