Fafnir2MM9118WIDULSuper-Precision Angular Contact Ball Bearing – 90 mm ID, 140 mm OD, 24 mm Width, Open, 15° Contact Angle, Phenolic Cage, Light Preload, Duplex Pair

Product Description

What this part is

Fafnir 2MM9118WI-DUL super-precision angular contact ball bearing, 90 mm bore, 140 mm outside diameter, 24 mm width, in the 9100WI spindle series. Steel rings and balls in a phenolic cage, open on both faces, supplied as a universally ground duplex pair set to light preload.

Decoding the designation

2MM is the Fafnir super-precision prefix at a 15° contact angle, built to P4S tolerances. In the 9100WI series the last two digits are the bore code, so 18 is 90 mm, and the envelope corresponds to an ISO 7018. DUL breaks down as D for duplex, U for universally ground and L for light preload, which is why two bearings make one set.

What these specs mean in practice

The 15° contact angle favours speed and radial stiffness; a 25° bearing in the same envelope trades speed for thrust capacity. The phenolic cage is light, tolerant of momentary lubrication starvation and quiet at speed, and is the usual choice for oil-lubricated spindle work. Light preload keeps heat generation and thermal growth low, which is what allows the 10,000 rpm limiting speed. Dynamic radial rating is 70.3 kN (15,800 lbf) and static radial rating 73 kN (16,400 lbf) per bearing. P4S tolerances hold bore, outside diameter, width and runout to the grade machine tool spindles are built around.

Quantity and configuration

Two bearings, one duplex pair. Universal grinding lets the pair be mounted back to back, face to face or in tandem and reach the ground light preload when clamped solid. Sale unit is 2 Pcs.

Installation and setup notes

Preload is built into the ground ring faces, so the pair is clamped against square shoulders with no shims between the rings. Ring faces carry the match marking and the pair is stacked to suit the chosen arrangement. Oil lubrication matches the cage material and speed rating.

Interchange guidance

Direct equivalents at 90 x 140 x 24 mm with a 15° angle and light-preload duplex grinding are SKF 7018 CD/P4ADGA, NSK 7018CTYNDULP4, FAG B7018-C-T-P4S-DUL and SNR 7018CVDUJ74. The 3MM9118WI version of this number is a 25° bearing in the same envelope, a related size rather than a substitution, and a 71918 is a different envelope at 90 x 125 x 18 mm.