FafnirSuper-Precision Angular Contact Ball Bearing 65 x 120 x 23 mm, Phenolic Cage, Open, Single

Product Description

What this part is

A Fafnir MM213WI-CR super-precision angular contact ball bearing, 65 mm bore by 120 mm outside diameter by 23 mm wide, open on both faces, with a phenolic cage riding on the outer ring land. Fafnir is Timken’s super-precision spindle bearing line and WI is its single-row angular contact spindle family. The ISO equivalent envelope is the 7213 size.

Decoding the designation

MM — P4 precision, ABEC 7 on dimensional and running tolerances. With no 9 ahead of the size block the bearing sits in the ISO 72 dimension series and the bore code 213 gives 65 mm. WI identifies the super-precision angular contact family and CR the phenolic outer-land-riding cage. There is no SU or DU block in the designation, so the bearing is furnished as a single unit rather than as part of a ground matched set.

What these specs mean in practice

P4 is a machine-tool class: form and running accuracy are held tight enough that the bearing itself is not the limit on spindle runout. The one-piece phenolic cage running on the outer ring land is light, quiet and self-lubricating, which is what allows the family to run at spindle speeds, and it sets a lower temperature ceiling than a brass cage would. Angular contact geometry takes radial load together with thrust in one direction, so the bearing is located axially by whatever opposes it in the spindle.

Quantity and configuration

1 Pc. Single bearing, not a ground matched set, and supplied without preload spacers or a mating bearing.

Interchange guidance

A direct interchange has to match this size, the P4 class and the contact angle marked on the ring. The 7213 envelope is also produced in 15°, 25° and 40° angles, and those are related sizes rather than substitutions because the split between radial and axial capacity moves with the angle. The Fafnir 2MM213WI is the 15° version of this size and the 3MM213WI the 25° version.