Fafnir2MM9111WI-DUMDuplex Super-Precision Angular Contact Bearing Pair – 55 mm ID, 90 mm OD, 18 mm Width, Open, 15° Contact Angle, Medium Preload, ABEC 7/9

Product Description

What this part is

Fafnir 2MM9111WI-DUM super-precision angular contact ball bearings, supplied as a duplex universally ground pair on the ISO 7011 C envelope. Bore: 55 mm. Outside Diameter: 90 mm. Overall Width: 18 mm per bearing. Contact Angle: 15°. Precision Class: P4S (ABEC 7/9). Cage Material: Phenolic. Cage Type: Machined. Preload: Medium. Mounting Arrangement: Duplex universal. Bore Type: Straight. Closure Type: Open. Number Of Rows: 1 per bearing. Rolling Elements: Balls. Bearing Material: Bearing steel. Series: 9100. Country of Origin: United States.

Decoding the designation

The 2MM prefix marks the Timken Fafnir super-precision range at a 15° contact angle, and it carries P4S tolerances. 9111 in the 9100WI series is Fafnir’s number for the ISO 70xx family, so 9111 is a 7011: 55 x 90 x 18 mm. DUM is the grouping and preload code: DU for a duplex universally ground set, M for medium preload. The carton also carries the forms 111HCDUM and 7011-C-T-DUM-P4.

What these specs mean in practice

Item Weight: 0.85 lb. Maximum Operating Temperature: 120 °C. Minimum Operating Temperature: -30 °C. Lubricant: grease or oil. A 15° contact angle carries more radial load and runs faster than a 25° or 40° angle, at lower thrust capacity, which is what suits it to machine-tool spindles and high-speed pump and gearbox positions. Medium preload sits between light and heavy: it buys more axial and radial stiffness than a light-preload set at the cost of some speed capability and a little more heat. The machined phenolic cage is light and quiet at speed, and it is what sets the 120 °C ceiling.

Quantity and configuration

Unit Quantity: 2 Pcs. DU marks a duplex universally ground set: both bearings have inner and outer rings of the same width with pre-adjusted faces, so the pair mounts back-to-back, face-to-face or in tandem and reaches the rated medium preload when clamped, with no ground spacer. New old stock.

Fitting notes

Bore Type: Straight, for an interference fit on the shaft with the inner ring rotating. Closure Type: Open, so lubricant is supplied from the housing. Harmonization Code: 8482.10.50.

Interchange guidance

Cross-Reference 1: SKF 7011 CD/P4ADGB, the same envelope at the same 15° contact angle with medium preload. Cross-Reference 2: 7011-C-T-DUM-P4. Cross-Reference 3: 111HCDUM. Searchable designation forms: 2MM9111WI-DUM, 2MM-9111-WI-DUM, 2MM9111WIDUM, 2 MM 9111 WI DUM, 2MM9111WI, 7011C and 7011-C.