FafnirSuper Precision Angular Contact Ball Bearing 40x80x18 mm, 25° Contact Angle, Phenolic Cage, ABEC 7, Universally Ground

Product Description

What this part is

A Fafnir 3MM208WI super-precision angular contact ball bearing with a phenolic cage, 40 mm bore x 80 mm outside diameter x 18 mm wide — the 7208 envelope. Bore Diameter: 40 mm. Outside Diameter: 80 mm. Width: 18 mm. Contact Angle: 25°. Number Of Rows: 1. Precision Class: ABEC 7. Cage Material: Phenolic laminated fabric, outer-land riding (CR). Bore Type: Straight. Closure Type: Open. It carries radial load plus thrust in one direction.

Decoding the designation

3 – in Timken/Fafnir super-precision numbering the numeric prefix names the contact angle: 3MM = 25°, 2MM = 15°.

MM – Fafnir super-precision tolerance, ABEC 7 (ISO P4). A single M is ABEC 3.

208 – 200 series, bore code 08, so a 40 mm bore.

WI – low shoulder on both rings, the duplex form.

CR – composition retainer: a phenolic laminated-fabric cage.

What these specs mean in practice

Contact Angle: 25°. This is the middle of the contact-angle range and the most broadly useful choice. Against a 15° bearing it gives noticeably more thrust capacity and axial stiffness; against a 40° bearing it gives more speed capability and less heat. It suits boring heads, milling spindles and precision drive shafts that see cutting thrust as well as speed, which is why 3MM is the most commonly stocked Fafnir super-precision prefix.

Precision Class: ABEC 7, which controls bore, outside diameter, width and above all radial and axial runout, so the ring can be fitted in any rotational orientation. Cage Material: phenolic, light, self-lubricating and quiet, rated for continuous service to roughly 120 °C.

Mounting data

Bore Diameter (d): 40 mm. Outside Diameter (D): 80 mm. Width (B): 18 mm. Rows: 1. Closure: open, no seals or shields. The high shoulder faces the thrust load, and a single angular contact bearing locates the shaft in one axial direction.

Quantity and configuration

Unit Quantity: 1 Pc. A single bearing, not a factory-matched duplex set. The WI series is universally ground, so two clamp face-to-face, back-to-back or in tandem and develop a repeatable preload. Factory-matched pairs carry the DUL, DUM and DUH designations to a named preload class.

Interchange guidance

Fafnir is now sold by Timken. Cross-Reference 1: SKF 7208 ACD/P4A. Cross-Reference 2: NSK 7208A5TYNP4. Cross-Reference 3: FAG B7208-E-T-P4S. All three are 40 x 80 x 18 mm at a 25° contact angle (SKF AC, NSK A5 and FAG E are the 25° codes).

Cross-Reference 4: NSK 7208A, the same size at a 30° contact angle. Cross-Reference 5: NSK 7208CTYNP4, the same size at 15°. Cross-Reference 6: Fafnir 2MM208WI, the same size at 15°. The B7208-E-T-DUL-P4 form that has travelled with this record names a duplex pair and is kept as a search term; this listing is one bearing.