Fafnir2MM220WISULSuper Precision Angular Contact Spindle Bearing Matched Pair 100 x 180 x 34 mm 15 Degree Contact Angle ABEC 7/9 P4S Light Preload Phenolic Cage

Product Description

What this part is

A matched pair of Fafnir super-precision angular contact ball bearings from the 200WI machine-tool spindle range, 100 mm bore × 180 mm outside diameter × 34 mm width each, 68 mm total width as a clamped set. This is a heavy-duty spindle bearing built for the working end of a machine tool: milling and boring spindle noses, grinding wheel heads, large rotary tables and precision gear-drive spindles. Fafnir became Torrington-Fafnir and is now the Timken Fafnir super-precision line, so the carton brand, the catalogue brand and the current supplier are three different names for the same bearing.

Decoding the designation

2MM is Timken/Fafnir’s code for a 15° contact angle; in this scheme 2MM is 15° and 3MM is 25°, and Timken’s own world part number for this bearing, 7220C-T-P4S-DUL, carries C for 15° in the universal scheme. 220: 200WI series, 100 mm bore. WI: the Fafnir super-precision spindle bearing range (9300WI, 9100WI, 200WI, 300WI). CR: phenolic outer-land-riding cage, with Timken listing the cage material as MBR. DU: duplex, universally ground, describing how two bearings behave together. L: light preload, with L light, M medium and H heavy. P4S: Timken publishes this bearing as ISO P4S, ABEC 7/9, and the carton itself is stamped ABEC 7; P4S is the tighter specification and is what Timken’s catalogue carries today.

What a 15° contact angle trades away

A 15° bearing carries its load closer to the radial plane than a 25° one. The payoff is speed and radial capability: a shallower angle means less centrifugal and gyroscopic loading on the balls, less ball spin at the contact, less heat, and a higher speed ceiling, here 8,000 rpm on grease and 16,000 rpm on oil. The cost is thrust capacity and axial stiffness, so the spindle deflects more axially under the same cutting thrust than a 3MM (25°) bearing of the same size. Thrust-dominated spindles use the 3MM equivalent.

Why the phenolic cage is worth paying for

The CR suffix means a machined phenolic cage that rides on the outer ring land rather than being guided by the balls. Phenolic is light and self-lubricating, so cage inertia stays low at speed, ball-to-pocket loads stay low, and the cage tolerates marginal or starved lubrication instead of galling, which is why phenolic never left the machine-tool spindle market even after polyamide took over general-purpose bearings. Land-riding rather than ball-riding guidance stabilises the cage at high speed and improves oil distribution through the bearing. That combination is what lets a 15° bearing reach 16,000 rpm on oil.

Preload class

On a duplex spindle set the preload class does as much work as the precision class. Light preload (DUL) runs cooler, draws less power, tolerates more thermal growth in the shaft and housing, and reaches higher speed. It delivers the least stiffness of the three classes, so the spindle deflects more under cutting load. Medium and heavy trade the other way. The class is matched across a stack, since an L clamped against an M comes up to a preload neither bearing was designed for.

What universal grinding lets you do

Universally ground, the U in DUL, means the ring faces are ground to a controlled offset so the pair comes up to its intended preload when clamped together, in any orientation, with no shims and no measuring. Arrangements: back-to-back (DB) for maximum moment stiffness and thrust in both directions, face-to-face (DF) where misalignment tolerance matters more than rigidity, tandem (DT) to double thrust capacity in one direction. The original Fafnir mounting instruction card for the WI series is included with this pair and shows the arrangements.

Published ratings

All figures below are from Timken’s own catalogue entry for 2MM220WICRDUL.

Bore 100 mm. Outside diameter 180 mm (7.087 in). Bearing width 34 mm (1.339 in) each; total width of the set 68 mm (2.677 in). Contact angle 15°. Precision rating ISO P4S (ABEC 7/9). Preload: light. Rows per set: duplex. Dynamic radial load rating C1, 1 million revolutions: 165,200 N (37,100 lbf) for the set. C1 ISO dynamic radial rating, per row: 150,000 N (33,700 lbf). Static radial load rating C0: 126,800 N (28,500 lbf). Limiting speed, grease: 8,000 rpm. Limiting speed, oil: 16,000 rpm. Ball type: steel. Cage: CR phenolic outer-land-riding, MBR cage material. Timken manufacturing part number: 2MM220WI DUL. Timken world part number: 7220C-T-P4S-DUL.

Quantity and configuration

This listing ships two bearings, one matched DUL pair. The photographs show two individually wrapped bearings alongside the Torrington-Fafnir carton and the original Fafnir WI-series mounting instruction card.

Condition

New old stock, made in USA, in the original Torrington-Fafnir carton with the factory label and the WI-series mounting instruction card. The bearings are unused and still in their factory wrappers. There is factory grease staining on the rings and inside the wrappers, which is normal on stored precision stock. The outer rings carry the factory THRUST marking that identifies the thrust-carrying face.

Mounting data

Maximum shaft fillet radius the bearing corners will clear: 2.1 mm (0.079 in). Outer ring “to clear” radius: 2.1 mm (0.079 in). Shaft backing shoulder diameter: 114.4 mm (4.510 in). Housing backing shoulder diameter: 166 mm (6.540 in).

Shaft and housing seats are ground to a tolerance and roundness consistent with a P4S bearing, since seat error transfers straight into spindle runout. The factory THRUST marking identifies the thrust-carrying face for orientation.

Interchange guidance

Fafnir became Torrington-Fafnir and then part of Timken, so a Fafnir part number search in a live catalogue works under Timken. Timken’s own world part number is 7220C-T-P4S-DUL, and the manufacturing part number is 2MM220WI DUL. Same-envelope 100 x 180 x 34 mm, 15°, P4-class universally ground light-preload pairs are also made by Schaeffler/FAG (B7220-C-T-P4S-DUL), NSK (7220CTYNDULP4) and SKF (7220 CD/P4ADGA). The sister designation 2MM220WICRDUM is the same bearing at medium preload, and 3MM220WICRDUL is the 25° version for thrust-dominated spindles. A substitution matches contact angle, preload class and tolerance class, and keeps one preload class within a stack.