Fafnir2MM218WIDULSuper Precision Angular Contact Ball Bearing 90 x 160 x 30 mm 15 Degree ABEC 7 Light Preload Phenolic Cage

Product Description

What this part is

A single-row super-precision angular contact ball bearing in the Fafnir 200WI spindle series, 90 mm bore × 160 mm outside diameter × 30 mm width. The ISO equivalent designation is 7218 C.

Decoding the designation

2MM — 15° contact angle, Fafnir super-precision spindle bearing.
218 — 200 dimension series, bore code 18, giving a 90 mm bore.
WI — spindle angular contact ball bearing, universally ground faces.
CR — phenolic cage riding on the outer ring land.
SU — single bearing, universally ground for matching.
L — light preload.

The MM prefix on a Fafnir spindle bearing carries P4S tolerances — ABEC 7 dimensional accuracy with ABEC 9 running accuracy.

What these specs mean in practice

A 15° contact angle biases the bearing toward speed and radial rigidity, and carries less thrust than a 25° bearing in the same envelope. Light preload keeps ball-to-race contact loads and heat generation low, which suits high-speed spindles where thermal growth rather than stiffness sets the limit. A medium or heavy preload in the same envelope trades that speed headroom for axial stiffness. Phenolic places the working temperature ceiling near 120 °C.

Published specifications

Bore: 90 mm (3.5433 in)
Outside diameter: 160 mm (6.2992 in)
Width: 30 mm (1.1811 in)
Contact angle: 15°
Precision class: ABEC 7 / ISO P4S
Preload: light (L)
Rows: 1
Cage: phenolic, outer-land-riding
Rolling elements: steel balls
Closure: open, both faces
ISO equivalent: 7218 C

Quantity and configuration

Single bearing, 1 Pc. Universal grinding allows it to be stacked back-to-back, face-to-face or in tandem with matching bearings of the same designation.

Fitting notes

Mounting is an interference fit on the shaft and a close fit in the housing bore, both held to super-precision spindle limits. Faces seat against square ground shoulders, and a runout error at the shoulder transfers directly into the raceway.

Interchange guidance

Same-spec 15° P4 equivalents in other schemes are the SKF 7218 CD/P4A, FAG B7218-C-T-P4S and NSK 7218CTR, matched for light preload. The 3MM218WI is a 25° bearing in the same envelope, and the SUM and SUH variants differ in preload — those are related sizes rather than interchanges.