FafnirM9307KMBRSpindle-Quality Deep Groove Ball Bearing 35 x 72 x 17 mm, Machined Bronze Cage, Open

Product Description

What this part is

A Fafnir M9307K-MBR spindle-quality deep groove ball bearing, 35 mm bore by 72 mm outside diameter by 17 mm wide, open on both faces with a machined bronze cage. Fafnir is Timken’s precision ball bearing line, and the 9100K, 200K and 300K blocks are its spindle deep groove ball bearing families — deep groove geometry built to spindle-grade accuracy rather than angular contact. The size sits in the 6207 envelope.

Decoding the designation

The M prefix marks the precision-ground spindle grade. The 9307 size and series block places the bearing in the spindle deep groove family, and K identifies that family in the Fafnir scheme. MBR is a machined bronze cage. There is no closure letter, so the bearing is open on both faces, and no clearance suffix, so it carries the family’s standard internal clearance.

What these specs mean in practice

Deep groove geometry takes radial load with thrust in either direction, which is what separates this family from an angular contact spindle bearing that takes thrust one way only. Built to spindle accuracy, it is used where a shaft needs low runout and quiet running without the axial stiffness of a preloaded angular contact set — grinder wheelheads, precision gear trains and instrument drives. A machined bronze cage is stiffer and far more heat-tolerant than a phenolic or polyamide cage, and it tolerates oil-mist and marginal lubrication better, at the cost of weight and top speed.

Quantity and configuration

1 Pc. Single bearing, open, with no seals, shields, snap ring or spacers.

Fitting notes

Mounting force is applied to whichever ring takes the tight fit, square to the ring face and never through the balls. Both rings seat fully against their shoulders. Spindle-grade fits are held tighter than general-purpose practice, and the bearing goes in clean and lubricated to its final oil or grease specification.

Interchange guidance

Interchange is on the 6207 envelope at a precision class and cage that match: an SKF or FAG 6207 in P5 or P6 with a machined cage is the nearest same-specification substitution. A standard commercial 6207 with a pressed steel cage shares the envelope but not the accuracy or the cage, so it is a related size. A 7207 angular contact bearing occupies the same envelope and is a different part entirely, since it takes thrust in one direction only.