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 — 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, confirms it: C is 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. Timken lists the cage material as MBR.
DU — duplex, universally ground. This describes how two bearings behave together; see the quantity section.
L — light preload. L light, M medium, H heavy.
P4S — Timken publishes this bearing as ISO P4S, ABEC 7/9. The carton itself is stamped ABEC 7. Both markings are genuine; 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: shallower angle means less centrifugal and gyroscopic loading on the balls, less ball spin at the contact, less heat, and a materially 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 would. If your spindle is speed-limited, 15° is the right choice; if it is thrust-limited and you are chasing axial rigidity, the 3MM equivalent is the bearing you actually want.

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. Two things follow. First, 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 exactly why phenolic never left the machine-tool spindle market even after polyamide took over general-purpose bearings. Second, land-riding rather than ball-riding guidance stabilises the cage at high speed and improves oil distribution through the bearing. This is the combination that lets a 15° bearing reach 16,000 rpm on oil, and it is a spec that surplus records almost never state.

Why the preload class matters more than the precision class:
Buyers read P4S and stop, but on a duplex spindle set the preload class does more work. Light preload (DUL) runs cooler, draws less power, tolerates more thermal growth in the shaft and housing, and reaches higher speed. It also 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 cannot be mixed within a stack: clamp an L against an M and you get a preload neither bearing was designed for, unloading one and overloading the other, and it shows up as heat and short life rather than as an obvious assembly fault. If you are replacing one bearing of an existing set, match the class.

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 simply clamped together, in any orientation, with no shims and no measuring. Mount back-to-back (DB) for maximum moment stiffness and thrust in both directions, face-to-face (DF) where misalignment tolerance matters more than rigidity, or in 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 and mounting data

All figures below are from Timken’s own catalogue entry for 2MM220WICRDUL — manufacturer data, not a distributor mirror.

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
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)
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. We photographed and counted them, because it matters: DUL describes how two bearings behave together, and duplex sets get split in surplus all the time, leaving one bearing in a carton still marked DUL. That has not happened here. The photographs show two individually wrapped bearings alongside the Torrington-Fafnir carton and the original Fafnir WI-series mounting instruction card. A buyer expecting a matched pair receives a matched pair. If you need a single, or a triplex or quadruplex stack, ask before ordering rather than assuming.

Correcting the source data

The previous description carried a dynamic load rating of 146 kN and a static rating of 153 kN. Both were wrong, and the static figure was implausibly higher than the correct dynamic one. Timken publishes 165.2 kN dynamic for the set, 150 kN dynamic per row, and 126.8 kN static. Those are now the published values. The precision rating was also given as ABEC 7 / P4 alone; Timken catalogues the bearing as P4S, ABEC 7/9, and we now state both that and the ABEC 7 stamp on the carton. A maximum operating temperature of 120 °C was quoted; Timken does not publish a temperature limit for this bearing, so it has been removed rather than repeated. The record also said nothing about the phenolic cage, the total set width, the limiting speeds or the pair configuration.

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 and is disclosed here rather than glossed over. The outer rings carry the factory THRUST marking that identifies the thrust-carrying face — use it when you orient the pair.

Fitting notes

Keep the pair together; splitting a universally ground set across two machines discards the reason it was bought. Observe the THRUST marking and the included Fafnir mounting card when orienting the rings. Shaft and housing seats must be ground to a tolerance and roundness worthy of a P4S bearing — installing an ABEC 7/9 bearing into an out-of-round or worn housing throws away the accuracy, and is the most common reason a rebuilt spindle still will not hold size. Respect the published abutment data: shaft backing shoulder 114.4 mm, housing backing shoulder 166 mm, and fillet radii no larger than 2.1 mm, or the bearing will sit on its corners instead of its faces. Press only on the ring taking the interference fit, never through the balls, clamp uniformly so preload comes up evenly, and lubricate to your spindle specification before running — note the large gap between the 8,000 rpm grease limit and the 16,000 rpm oil limit when you choose.

Interchange guidance

Fafnir became Torrington-Fafnir and then part of Timken, so a Fafnir part number search in a live catalogue only works under Timken — that obsolescence trail is the single most common reason buyers cannot find this bearing. 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). Note the sister designation 2MM220WICRDUM, which is the same bearing at medium preload — stiffer, hotter, slower — and 3MM220WICRDUL, which is the 25° version for thrust-dominated spindles. Match contact angle, preload class and tolerance class before substituting, and never mix preload classes inside one stack.