FafnirM209KCRDeep Groove Ball Bearing 45x85x19 mm, Phenolic Cage, ABEC 3 / P6 Precision, Open — 3 Pcs

Product Description

What this part is

A Fafnir M209K single-row deep groove ball bearing with a composition (phenolic) cage, 45 mm bore x 85 mm outside diameter x 19 mm wide — the standard 6209 / 209 envelope, built to a precision tolerance class rather than the ordinary commercial grade. It is open on both sides: no seals, no shields, no snap ring.

Decoding the designation

M – Fafnir tolerance class ABEC 3, equivalent to ISO P6. Watch this letter: a single M is ABEC 3, a doubled MM is the ABEC 7 super-precision grade, and M with an FS6xxxx suffix is ABEC 5. One letter, three different answers, and it is the most misread element of Fafnir numbering.
209 – 200 series, bore code 09, so 45 mm bore.
K – Fafnir series code for a plain single-row deep groove (Conrad) radial ball bearing, open on both sides.
CR – composition retainer, i.e. a phenolic laminated-fabric cage. Fafnir stamps CR on the carton rather than on the ring, so the bearing itself may read only M209K.

What these specs mean in practice

A deep groove ball bearing takes radial load plus moderate thrust in both directions and is the default wherever a shaft simply needs supporting. What makes this one worth specifying is ABEC 3 tolerance together with a phenolic cage. ABEC 3 tightens bore, outside diameter, width and runout beyond a standard bearing, so shaft and housing fits land where the drawing says and the shaft runs truer — the grade used for machine spindles, precision gear drives and instrument shafting.

The phenolic cage is a high-speed feature. It is light, so cage inertia and cage-driven noise are low; it is self-lubricating, so it survives marginal lubrication; and it is soft enough that a ball skid polishes the pocket instead of galling it. The trade-off is heat and chemistry: phenolic does not like sustained temperature much above roughly 120 °C, and some synthetic lubricants and cleaning solvents attack the resin. Check the cage material against your lubricant, and do not steam clean it.

Published dimensions

Bore (d): 45 mm
Outside diameter (D): 85 mm
Width (B): 19 mm
Rows: 1
Type: deep groove (Conrad) radial ball bearing
Cage: phenolic / laminated fabric composition
Precision: ABEC 3 / ISO P6
Closure: open both sides, no seals or shields, no snap ring

Quantity and configuration

This listing supplies three bearings. Each is a complete, non-separable bearing — inner ring, outer ring, ball complement and cage. They are not a matched set: a deep groove bearing carries no ground face offset, so there is no supplied preload and no set orientation to preserve.

Fitting notes

Press or induction-heat onto the shaft against the inner ring only, and press into the housing against the outer ring only — never route mounting force through the balls, and never strike a phenolic cage. Grease to roughly a third fill for high-speed service; overpacking a phenolic-cage bearing is what cooks the cage. Because the bearing is open it relies entirely on the housing for sealing, so give it a shaft seal or a labyrinth in a dirty environment.

Interchange guidance

Fafnir is now sold by Timken, so Timken M209KCR and Fafnir M209KCR are the same part. The 45 x 85 x 19 mm open deep groove envelope is an ISO standard, so dimensional equivalents are SKF 6209, NSK 6209, FAG 6209, NTN 6209, Koyo 6209 and MRC 209S. Naming the difference that matters: a plain 6209 from any of those makers is normal (P0) tolerance with a pressed steel cage, so it is a dimensional substitute but not a precision or high-speed one. For like-for-like ask for the P6 / ABEC 3 grade with a phenolic or nylon cage — NSK 6209P6 or FAG 6209-P6. Adjacent Fafnir numbers: 209K is the same bearing in standard tolerance, and 9109K is the thin 6009 envelope, not this one.