Fafnir2MM9115WI-SULSuper-Precision Angular Contact Ball Bearing – 75 mm ID, 115 mm OD, 20 mm Width, Open, 15 Degree, Light Preload, Single Universally Ground

Product Description

What this part is

Fafnir 2MM9115WI-SUL super-precision angular contact ball bearing, 75 mm bore, 115 mm outside diameter, 20 mm width. Single bearing, universally ground, open on both faces, chrome steel rings and balls with a phenolic cage. The ISO equivalent is a 7015 at 15°.

Decoding the designation

The 2MM prefix marks a 15° contact angle in the Fafnir super-precision scheme, and the MM prefix itself carries the P4S precision class, ABEC 7/9. 9115 places the bearing in the 9100WI series, which maps to the ISO 70 light dimension family, giving a 7015 envelope. WI is the series designation. SUL is a single universally ground bearing at light preload.

What these specs mean in practice

A 15° contact angle favours speed and radial stiffness over thrust capacity, which is why the 9100WI series is standard in machine tool spindles and grinding heads. Dynamic load rating 47.4 kN, static load rating 28.2 kN, limiting speed 14,000 rpm, maximum temperature 121 °C. The phenolic cage is light and low friction, which is what supports that speed figure, and it prefers oil or oil-air lubrication. Light preload gives lower running heat and higher speed capability than a medium or heavy preload, at some cost in stiffness.

Quantity and configuration

One bearing, universally ground. A universally ground single can be paired with another of the same designation to make a back-to-back, face-to-face or tandem set, and the ground offset then establishes light preload across the pair. Because the bearing is preloaded rather than clearance-set, it carries no radial internal clearance value.

Fitting notes

Straight bore on an interference fit shaft seat, outer ring located in a bored housing. Preload comes from the ground ring offset, so no shims or spacers are required when two universally ground bearings are mounted together.

Interchange guidance

Same-specification equivalents at 15° in this envelope are the SKF 7015 CD/P4A, FAG B7015-C-T-P4S and NSK 7015CTYNP4. A 3MM9115WI shares the 75 x 115 x 20 mm envelope at a 25° contact angle, making it a related size rather than an interchange, and a DUL version of this number is a matched pair rather than a single.