Fafnir3MM212WIDUHSuper Precision Angular Contact Ball Bearing Matched Duplex Pair 60 x 110 x 22 mm 25 Degree ABEC 7 Heavy Preload

Product Description

What this part is

A matched duplex pair of super-precision angular contact ball bearings in the Fafnir 200WI spindle series, each 60 mm bore × 110 mm outside diameter × 22 mm width. The ISO equivalent designation is 7212 A, also written 7212-A5 in the NSK scheme.

Decoding the designation

3MM: 25° contact angle, Fafnir super-precision spindle bearing. 212: 200 dimension series, bore code 12, giving a 60 mm bore. WI: spindle angular contact ball bearing, universally ground faces. CR: phenolic cage riding on the outer ring land. DU: duplex, a factory-matched set of two. H: heavy preload. The MM prefix carries P4S tolerances — ABEC 7 dimensional accuracy with ABEC 9 running accuracy.

Specifications

Bore: 60 mm (2.3622 in). Outside Diameter: 110 mm (4.3307 in). Overall Width: 22 mm (0.8661 in) per bearing. Total Width: 44 mm (1.7323 in) across the duplex pair. Contact Angle: 25°. Precision Class: ABEC 7 / ISO P4S. Preload: Heavy (H). Number Of Rows: 1 per bearing. Cage Material: Phenolic, fabric-reinforced laminate. Cage Type: Outer-land-riding. Rolling Elements: Steel balls. Closure Type: Open, both faces. Bore Type: Straight. Material: High carbon chrome steel. Design Units: Metric. Series: 200WI. Base Number: 7212. Dynamic Load Rating: 61.8 kN (13,900 lbf). Static Load Rating: 53.4 kN (12,000 lbf). Limiting Speed: 14,000 rpm. Running Accuracy, Radial and Axial Runout: 0.0025 mm. Lubricant: Oil or grease. Item Weight: 1.76 lb. Harmonization Code: 8482.10.5028. UNSPSC: 31171504.

What these specs mean in practice

A 25° contact angle carries substantially more thrust and gives higher axial stiffness than a 15° bearing in the same envelope, and gives up speed capability in exchange. Heavy preload pushes axial and radial stiffness higher again, at the cost of friction and heat, which places this combination on rigid, well-cooled spindles handling significant thrust rather than on the highest-speed grinding heads. The phenolic cage places the working temperature ceiling near 121 °C.

Quantity and configuration

Matched duplex pair, 2 Pcs. The two bearings are ground as a set, and the pair carries the heavy preload as supplied.

Interchange guidance

Same-spec 25° P4 duplex equivalents in other schemes are the SKF 7212 ACD/P4ADGB, FAG B7212-E-T-P4S-DUH and NSK 7212A5TRDUH. The 2MM212WI is a 15° bearing in the same envelope, and the DUL and DUM variants differ in preload — those are related sizes rather than interchanges.