Fafnir2MM9111WISuper-Precision Spindle Angular Contact Ball Bearing – 55 mm ID, 90 mm OD, 18 mm Width, Open, 15° Contact Angle, ABEC 7/9

Product Description

What this part is

Fafnir 2MM9111WI super-precision spindle angular contact ball bearing. Bore: 55 mm. Outside Diameter: 90 mm. Overall Width: 18 mm. Number Of Rows: 1. Rolling Elements: Ball. Bore Type: Straight. Closure Type: Open. Bearing Material: chrome bearing steel. Series: 9100WI, the Fafnir spindle series that maps to ISO 70xx, so this size is a 7011. Item Weight: 0.84 lb (0.38 kg).

Decoding the designation

Contact Angle: 15°, set by the 2MM prefix of the 2MM9100WI series. Precision Class: P4S, equivalent to ABEC 7/9. Cage Material: laminated phenolic. Cage Type: machined, outer-ring land-riding. Bore code 9111 maps to ISO 7011, a 55 mm bore. Searchable forms of the number: 2MM9111WI, 2MM-9111-WI-CR, 2MM 9111 WI CR, 7011-C.

Load ratings and speed

Dynamic Load Rating: 37.8 kN (8,500 lbf). Static Load Rating: 28.6 kN (6,420 lbf). Limiting Speed: 14,700 rev/min. Maximum Operating Temperature: 120 °C, set by the phenolic cage.

What these specs mean in practice

A 15° contact angle favours speed and radial rigidity over thrust capacity, which is the standard choice for a machine-tool spindle rather than a heavily thrust-loaded position. P4S is a step tighter than P4: ABEC 7 dimensional tolerances with ABEC 9 running accuracy, which is what holds a spindle’s radial and axial runout down at speed. The phenolic cage rides on the outer ring land, so the cage is guided by a stationary surface at high speed and the material’s low mass and self-lubricating character keep cage friction and heat down.

Quantity and configuration

Unit Quantity: 1 Pc. Mounting Arrangement: single universal. The rings are universally ground, so any two of these bearings clamp together back-to-back or face-to-face at the rated preload and share load equally in tandem. Internal Clearance: N/A. A universally ground super-precision bearing is preload-set rather than clearance-set.

Fitting notes

Lubricant: grease or oil. The high point of radial runout is marked on the rings; aligning those marks between paired bearings and opposing them to the shaft or housing eccentricity minimises assembled runout.

Interchange guidance

Carton designation carried on this part: 7011 C TR/TY P4/P4Y. Same-envelope 15° super-precision executions in other schemes: SKF 7011 CD/P4A, NSK 7011CTRSU, RHP 7011CTSUL and FAG B7011-C-T-P4S-UL. A 3MM9111WI carries a 25° contact angle in the same 55 x 90 x 18 mm envelope, which makes it a related size rather than a substitution.