Fafnir3MM211WITULAngular Contact Ball Bearing – 55 mm ID, 100 mm OD, 21 mm Width, Open, 25°, Light Preload, Universal Triplex Set

Product Description

What this part is

Fafnir 3MM211WITUL super-precision angular contact ball bearing, supplied as a universally ground matched triplex set of three. Bore 55 mm, outside diameter 100 mm, width 21 mm per bearing, 63 mm across the set. ISO equivalent size 7211. Fafnir is a Timken brand.

Decoding the designation

The 3MM prefix gives a 25° contact angle, and the MM series is built to P4S, equivalent to ABEC 7 bore and outside-diameter tolerances with ABEC 9 running accuracy. 211 is the ISO 200-series size, so 7211. WI is the super-precision angular contact execution. CR is the phenolic outer-land-riding cage. TUL is a triplex universal set at light preload.

What these specs mean in practice

A 25° contact angle carries substantially more thrust than a 15° bearing of the same size and gives higher axial stiffness, at the cost of speed capability. Three bearings in one stack raise thrust capacity and stiffness further in the loaded direction. Light preload keeps heat generation low, which suits continuous high-speed spindle duty. Limiting speed 18,000 rpm; the phenolic cage sets the upper temperature limit at 121 °C.

Quantity and configuration

Three bearings, matched as one set. Universal grinding means the stack can be arranged as tandem-plus-one opposed, triple tandem, or back-to-back combinations, with preload established as the ground faces are clamped together.

Preload and clearance

Light preload, ground into the ring faces. A preloaded matched set carries no operating radial internal clearance, so clearance classes such as CN do not apply.

Fitting notes

Each outer ring carries a V mark across the outside diameter; the marks are aligned in the intended stack order. Shaft and housing seats are held to precision tolerances, and the three bearings are clamped as a single unit against a common shoulder.

Interchange guidance

FAG B7211-E-T-P4S-TUL is a same-specification interchange — the E on a B70 designation is a 25° contact angle, T is the phenolic cage, and TUL matches the triplex universal light-preload arrangement. NSK 7211A5TRSUV1V3 is the same size and angle as universal singles, so three are needed to build the equivalent stack. SKF 7211 ACD/P4A is the same envelope and angle as a universal single, a related arrangement rather than a drop-in for a matched triplex.