Fafnir3MM9124WIDULSuper-Precision Angular Contact Ball Bearing Duplex Pair, 120 mm Bore, 180 mm OD, 28 mm Width, 25 Degree Contact Angle, Light Preload, ABEC 7 / P4S

Product Description

What this part is

Fafnir 3MM9124WI-CR-DUL matched duplex pair of super-precision single-row angular contact ball bearings, universally ground. Bore: 120 mm (4.724 in). Outside Diameter: 180 mm (7.087 in). Bearing Width: 28 mm (1.102 in) per bearing. Total Width: 56 mm (2.205 in) as a pair. Series: Fafnir 9100WI spindle series, ISO 7024 envelope. Timken World Part Number: 7024E-T-P4S-DUL. GTIN: 087796073210. Rolling Elements: steel balls. Bearing Material: chrome steel. Cage Type: CR — Phenolic Outer Land Riding Cage. Cage Material: phenolic textile laminate. Closure Type: open. Number of Rows: 1 per bearing.

Decoding the designation

Contact Angle: 25°. Precision Rating: ISO P4S (ABEC 7/9). Preload: Light. 3MM is the Fafnir super-precision prefix at the 25° angle, and the MM prefix carries the P4S build. The Fafnir 91xx block maps to the ISO 70xx dimension series, so 9124 is the 7024 envelope at 120 x 180 x 28 mm. WI identifies the super-precision angular contact spindle family with a low shoulder on both rings. CR is the phenolic cage riding on the outer ring land. DUL is a duplex pair, universally ground, at light preload. Searchable forms of the number include 3MM9124WI-DUL, 3MM9124WIDUL, 3MM9124WICRDUL, 3MM-9124-WI-CR-DUL, 3MM 9124 WI CR DUL and 7024-E.

What these specs mean in practice

Dynamic Load Rating (C1, Timken 1M revs, set): 105 kN / 23,600 lbf. Dynamic Load Rating (C1 ISO, per row): 95.6 kN / 21,500 lbf. Static Load Rating (C0): 103.2 kN / 23,200 lbf. Limiting Speed, grease: 6,900 rpm. Limiting Speed, oil: 12,400 rpm. A 25° contact angle carries substantially more thrust than a 15° bearing of the same envelope and gives a stiffer axial response, in exchange for top speed. Light preload runs with the lowest torque and the least heat of the three grades, which suits the higher end of the speed range, and it gives up some axial stiffness against medium and heavy settings. The phenolic outer-land-riding cage, at roughly a fifth the density of brass, loads itself far less under centrifugal force, and the laminate holds a small oil reserve; outer-land riding keeps the cage guided by the outer ring so it stays concentric at speed.

Mounting dimensions

Shaft Backing Shoulder Diameter: 132.5 mm (5.220 in). Housing Backing Shoulder Diameter: 168.3 mm (6.630 in). Maximum Shaft Fillet Radius: 2 mm (0.079 in). Outer Ring To Clear Radius: 2 mm (0.079 in). Bore Type: straight.

Quantity and configuration

Unit Quantity: 2 Pcs, one matched duplex pair. Rows per set: duplex. Item Weight: 9.62 lbs for the pair, 4.81 lbs per bearing. Universal grinding lets the pair clamp back-to-back for two-direction thrust and the widest effective bearing spread, face-to-face for a narrower spread, or in tandem to double one-direction thrust, each arrangement developing the specified light preload when clamped solid.

Interchange guidance

A same-specification equivalent duplex pair is the SKF 7024 ACD/P4ADGA. Timken’s own world part number for this set is 7024E-T-P4S-DUL, and E denotes the 25° angle in that scheme. The 15° 2MM9124WI-CR-DUL shares the envelope at a different contact angle, and the DUM and DUH suffixes are the same pair at medium and heavy preload; all three are related sizes rather than substitutions, because contact angle and preload set the stiffness and speed behaviour of the mounting.