Fafnir3MM209WICRDUHSuper-Precision Angular Contact Ball Bearing 45x85x19 mm 25° ABEC 7/9 Heavy Preload Phenolic Cage

Product Description

What this part is

A Fafnir 3MM209WICR-SUH super-precision single-row angular contact ball bearing, 45 mm bore by 85 mm outside diameter by 19 mm width. It is a spindle bearing for machine tools, precision grinders, high-speed gearboxes and rotary tables, ground so that it can be built into a matched multi-bearing stack.

Decoding the designation

3MM — 25° contact angle in the Fafnir scheme; the MM prefix also denotes P4S precision, ABEC 7/9209 — 72-series envelope, 45 x 85 x 19 mmWI — Fafnir super-precision angular contact ball bearing seriesCR — machined phenolic cage, riding on the outer ring landSU — single universally groundH — heavy preload

What these specs mean in practice

The 25° contact angle gives high thrust capacity and high axial stiffness while still supporting fast running, which is what a milling or drilling spindle needs when the cut loads the shaft along its axis as well as across it.

Heavy preload is a deliberate stiffness choice. It raises the spindle’s axial and radial stiffness and improves running accuracy under load, and it raises operating temperature and lowers the safe speed ceiling relative to light or medium preload. It belongs where cut accuracy under load matters more than maximum spindle speed.

The phenolic outer-land-riding cage is light, self-lubricating and quiet, and riding on the outer land keeps the cage stable at speed. Phenolic carries a lower temperature ceiling than machined brass, so it belongs in oil-mist, oil-air or light-grease systems.

P4S is a tighter precision grade than P4: bore, outside diameter and running accuracy are held to ABEC 7 limits with ABEC 9 running accuracy. That is what keeps measured spindle runout to a couple of microns.

Published specifications

Bore: 45 mmOutside diameter: 85 mmWidth: 19 mmRows: 1Contact angle: 25°Precision class: P4S, ABEC 7/9Preload: heavyCage: machined phenolic, outer-land ridingClosure: open

Quantity and configuration

This listing supplies one bearing. Building a matched pair or triplet requires additional bearings of the same designation. Spacer rings, lock nuts and housings are not included.

Fitting notes

The high shoulder on the outer ring shows the contact angle direction and sets the arrangement. Back-to-back carries moment load and is the usual spindle configuration; face-to-face tolerates slight misalignment; tandem doubles thrust capacity in one direction. Universal grinding means any two bearings of this designation form a set at the tabulated heavy preload without shimming. P4S accuracy survives only on shaft and housing seats held to matching roundness and cylindricity limits, and the rings are pressed on by their faces rather than through the balls.

Interchange guidance

Genuine equivalents are 7209-envelope super-precision bearings at 25° with heavy preload and P4S class, including the ISO-scheme 7209A5 form and equivalents such as NSK 7209A5TRSUH and SKF 7209 ACD/P4A in its heavy-preload single-ground variant. The 2MM209WICR-SUH is a different part — the 2MM prefix is a 15° contact angle. Light and medium preload forms (SUL, SUM) and the duplex-ground DUH form are related variants rather than substitutions.