Fafnir2MM9117WIDUHSuper Precision Angular Contact Ball Bearing — 85 x 130 x 22 mm, 15° Contact Angle, Phenolic Cage, Duplex Heavy Preload, Open

Product Description

What this part is

A Fafnir 2MM9117WI-DUH super-precision angular contact ball bearing set, supplied as a duplex universally ground pair. Bore is 85 mm, outside diameter 130 mm and each ring width 22 mm. The bore is straight, both faces are open, and the cage is phenolic. The ISO equivalent is a 7017 C pair. Fafnir is Timken’s super-precision spindle bearing brand.

Decoding the designation

The leading 2MM sets a 15° contact angle, and the MM prefix carries the P4S precision grade, which is ABEC 7/9. The leading 9 in 9117 places the bearing in the ISO 70 light dimension series, so the ISO number is 7017; the bore code 17 gives 85 mm at five millimetres per unit. WI marks the super-precision spindle grind, CR marks the phenolic outer-land-riding cage, DU marks universally ground faces for duplex mounting, and the trailing H sets heavy preload, the stiffest of the L, M and H series.

What these specs mean in practice

A 15° contact angle keeps the ball path close to radial, which limits thrust capacity per row but raises the achievable speed and lowers heat generation; the 13000 rpm limiting speed on this size reflects that. Heavy preload trades in the other direction, buying axial and radial stiffness and tight positional repeatability at the cost of running torque and heat, so it belongs on a rigid spindle carrying real cutting load rather than on a lightly loaded high-speed head. The phenolic cage is light and self-lubricating and rides on the outer ring land, which carries oil through the pockets and keeps cage mass low at speed. It also sets the 121 °C upper temperature limit. Ratings for the pair are 75.4 kN (16951 lbf) dynamic and 76.5 kN (17198 lbf) static; the static figure exceeds the dynamic figure because pairing multiplies the two ratings by different factors, roughly 1.62 on dynamic and 2.0 on static.

Quantity and configuration

2 Pcs, a universally ground duplex pair at heavy preload, supplied open with no snap ring and no relubrication feature.

Mounting arrangement

Universal grinding allows back-to-back, face-to-face or tandem assembly with the specified preload delivered by the ground ring offsets. Back-to-back gives the widest effective spread and the best moment stiffness; face-to-face narrows the spread and tolerates slightly more seat misalignment; tandem stacks both rows for one-direction thrust at roughly double single-row axial capacity.

Fitting notes

Preload comes from the ground offsets, so no spacer grinding is needed at assembly. Rings take a light interference fit on the shaft and a close fit in the housing. Because the bearings are open, oil supply, drainage and sealing are functions of the spindle rather than of the bearing. Operating range is −30 °C to 121 °C.

Interchange guidance

SKF 7017 CD/P4ADGC, FAG B7017-C-T-P4S-DUH and NSK 7017CTYNDUHP4 are the same size, angle and heavy-preload duplex arrangement and are direct interchanges. A 3MM9117WI pair shares the envelope at a 25° contact angle and is a related size, since the angle change alters both thrust capacity and speed. 2MM9117WI-DUL and -DUM are the same bearing at light and medium preload and are different stiffness classes.