Fafnir2MM9102WI DULSuper-Precision Angular Contact Ball Bearing Matched Pair 15 x 32 x 9 mm, 15° Contact Angle, Light Preload, Open, ISO P4S

Product Description

What this part is:

A matched pair of Fafnir super-precision single-row angular contact ball bearings, spindle grade, in the 9100WI series. Bore: 15 mm (0.5906 in). Outside diameter: 32 mm (1.2598 in). Width: 9 mm (0.3543 in) per bearing. Total width: 18 mm (0.7087 in) across the pair. The pair is universally ground so it can be clamped back-to-back, face-to-face or in tandem, and it develops a light preload when the ring faces are clamped solid. The 9100WI series carries the metric 70-series envelope, so this size corresponds to a 7002 dimensionally.

Decoding the designation:

2MM: 15° initial contact angle in the Fafnir WI spindle scheme. MM prefix: super-precision grade, ISO P4S (ABEC 7/9). 9102: 9100WI series, bore code 02, the 15 x 32 x 9 mm envelope. WI: Fafnir spindle angular contact ball bearing family. DU: duplex universal grinding, so any two bearings of the designation form a matched set. L: light preload.

Verified performance data:

Contact angle: 15°.

Dynamic radial load rating C1: 7,300 N (1,630 lbf) per bearing.

Static radial load rating C0: 3,600 N (820 lbf) per bearing.

Limiting speed, grease: 48,800 rpm.

Limiting speed, oil: 97,200 rpm.

Precision class: ISO P4S (ABEC 7/9).

Cage type: Phenolic, outer-land-riding.

Rolling elements: Steel balls.

Number of rows: single row per bearing, two rows per set.

Bore type: Straight.

Seal type: Open.

What these specs mean in practice:

A 15° contact angle is the speed-biased end of the spindle-bearing range: less axial capacity and axial stiffness per row than a 25° bearing of the same envelope, lower ball-to-race friction, less preload-driven heat rise, and a higher usable speed. Fafnir describes the 2MM-WI types as intended to run at the lowest practical temperature across a wide span of speeds and loads. Light preload extends that further, trading a measure of radial and axial rigidity for thermal headroom. P4S running accuracy holds runout tight enough for grinding and boring spindles, where the bearing tolerance rather than the shaft dominates the achievable concentricity.

Quantity and configuration:

Duplex universal matched pair, light preload, two bearings supplied as one set. The C1 and C0 ratings above are stated per bearing.

Preload and clearance:

Internal clearance: preloaded, light preload developed as the universally ground ring faces are clamped solid.

Mounting data:

Universal grinding means the ring faces are finished so that either mating orientation produces the published preload once the faces are clamped solid against square, ground abutments. Back-to-back gives the greatest moment stiffness and accepts thrust in both directions; face-to-face tolerates differential shaft and housing growth; tandem shares thrust in one direction between the two rows. Adding shims between the pair alters the developed preload away from the light setting. Lubricant: grease or oil.

Interchange guidance:

Dimensionally this set occupies the 7002 envelope, so the equivalent super-precision 15° light-preload pairs from other schemes are the SKF 7002 CD/P4ADGA, FAG 7002-C-T-P4S-DUL and NSK 7002CTYNDBLP4. Related sizes sharing the 15 x 32 x 9 mm envelope but differing in contact angle, preload or grinding — 3MM9102WI at 25°, 2MM9102WI-DUM at medium preload, 2MM9102WI-SUL as a single bearing — are different parts.