Fafnir3MM9118WI-DULSuper Precision Angular Contact Ball Bearing Matched Pair 90 x 140 x 24 mm, 25° Contact Angle, P4S / ABEC 7 Class, Duplex Light Preload, 2 Pieces

Product Description

What this part is

Fafnir 3MM9118WI-DUL super-precision angular contact ball bearing, supplied as a universally ground duplex pair. Bore: 90 mm. Outside Diameter: 140 mm. Bearing Width: 24 mm. Total Width: 48 mm. Series: Fafnir 9100WI spindle series, ISO 7018 envelope. Timken World Part Number: 7018E-T-P4S-DUL. Rolling Elements: steel balls. Cage Type: CR – Phenolic Outer Land Riding Cage. Cage Material: phenolic. Closure Type: open on both faces.

Decoding the designation

3MM is the Fafnir super-precision prefix. Contact Angle: 25°. Precision Rating: ISO P4S (ABEC 7/9). The Fafnir 91xx block maps to the ISO 70xx dimension series, so 9118 is the 7018 envelope at 90 x 140 x 24 mm. WI identifies the super-precision angular contact spindle family. DUL is duplex, universally ground, light preload. Preload: Light. Searchable forms of the number include 3MM9118WI-DUL, 3MM9118WIDUL, 3MM-9118-WI-DUL and 3MM 9118 WI DUL.

What these specs mean in practice

Dynamic Radial Load Rating (C1, set): 75.2 kN / 16,900 lbf. Dynamic Radial Load Rating (C1, per row): 68.5 kN / 15,400 lbf. Static Radial Load Rating (C0): 65.8 kN / 14,800 lbf. Limiting Speed, grease: 8,300 rpm. Limiting Speed, oil: 16,600 rpm. The 70xx series is the thin-section spindle family, a slim ring for a 90 mm bore, which keeps mass and outside diameter down and lets the bearing run faster than a heavier 72xx section. A 25° contact angle is the middle setting: against a 15° bearing it carries more thrust and gives a stiffer axial response, and against a 30° or 40° bearing it runs faster and cooler. Light preload brings less internal friction, less heat and higher permissible rpm, at the cost of some stiffness against cutting load. Universal grinding is what makes these usable as a set: the ring faces are ground so that clamping any two of them together produces a known, repeatable preload.

Mounting dimensions

Shaft Backing Shoulder Diameter: 99.7 mm (3.930 in). Housing Backing Shoulder Diameter: 130.9 mm (5.160 in). Maximum Shaft Fillet Radius: 1.5 mm (0.059 in). Outer Ring To Clear Radius: 1.5 mm (0.059 in).

Quantity and configuration

Two bearings, one duplex pair. Unit Quantity: 2 Pcs. Universal grinding lets the pair mount back to back for maximum moment stiffness and thrust in both directions, face to face where the housing bores may be slightly out of line, or in tandem to double thrust capacity in one direction. The light preload develops when the pair is clamped between the shaft shoulder and the locknut.

Interchange guidance

Fafnir super precision is supplied under the Timken brand. Same-envelope 25° equivalents include NSK 7018A5, FAG B7018-E-T-P4S-UL, SKF 7018 ACD/P4A, RHP 7018-E-T-DUL-P4 and NTN 7018 in the matching precision grade. Timken’s own world part number for this bearing is 7018E-T-P4S-DUL, and E denotes the 25° angle in that scheme. The 7018-C reference also carried on this listing shares the 90 x 140 x 24 mm envelope and is a dimensional cross-reference; C denotes 15°. The 15° sibling of this bearing is 2MM9118WI, a related size rather than a substitution.