FafnirM209KDeep Groove Ball Bearing 45x85x19 mm, ABEC 3 / P6 Precision, Open Both Sides

Product Description

What this part is

A Fafnir M209K single-row deep groove ball bearing, 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. Open on both sides: no seals, no shields, no snap ring.

Decoding the designation

M – Fafnir tolerance class ABEC 3, equivalent to ISO P6. Read this letter carefully: 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 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 both sides.

What these specs mean in practice

A deep groove ball bearing takes radial load plus moderate thrust in both directions, which is why it is the default wherever a shaft simply needs supporting. The reason to specify this one is the tolerance grade. ABEC 3 / P6 tightens bore, outside diameter, width and running accuracy 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, indexing heads and instrument shafting. In an ordinary pump or fan position a standard 6209 does the same job; specify P6 when running accuracy or repeatable fit-up is what the machine is being judged on.

Published dimensions

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

Quantity and configuration

Sold as one bearing — inner ring, outer ring, ball complement and cage as a single non-separable unit. Not a matched set and not preloaded; a deep groove bearing has no ground face offset, so there is 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. 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. Grease to roughly a third fill for higher-speed service.

Interchange guidance

Fafnir is now sold by Timken, so Timken M209K and Fafnir M209K are the same part. The 45 x 85 x 19 mm open deep groove envelope is an ISO standard, so SKF 6209, NSK 6209, FAG 6209, NTN 6209, Koyo 6209 and MRC 209S all describe the same envelope. Naming the difference that matters: those plain numbers are normal (P0) tolerance, so they are dimensional substitutes but not precision ones — for like-for-like ask for NSK 6209P6 or FAG 6209-P6. Within Fafnir, 209K is the same bearing in standard tolerance, M209KCR is this bearing with a phenolic cage, and 9109K is the thinner 6009 envelope rather than this one.