NSK7211CTRDUMP4YSuper-Precision Angular Contact Spindle Bearing, 55x100x21 mm, 15° Contact Angle, Universally Ground Single, Medium Preload, ABEC 7 (P4)

Product Description

What this part is

This is a single super-precision angular contact ball bearing in the 55 mm bore x 100 mm outside diameter x 21 mm width envelope — the ISO 7211 size.

Decoding the designation

Reading the suffixes: C is a 15 degree contact angle, TR denotes the cage type, M is medium preload, and P4 is ABEC 7 precision.

Quantity and configuration

One bearing is supplied. Note on the part number, because it matters when you cross-check against the box: the original NSK carton is marked 7211CTRDUMP4Y, where DUM means duplex universal medium preload — a factory-matched pair. This listing is a single bearing from such a set, so it is offered as SUM (single universal medium) to describe what actually ships. Both designations are given here so the listing is findable either way.

Fitting notes

Because the rings are universally ground, this bearing can be mounted alone, or paired with another universally ground bearing of the same designation and preload class back-to-back (DB), face-to-face (DF) or in tandem (DT), reaching the specified preload with no shimming or custom grinding — the three arrangements shown on the NSK leaflet supplied with the bearing.

Why the preload class matters

Medium preload sits between light and heavy: more axial rigidity and tighter shaft location than light, without the heat generation that limits heavy preload at speed. A 15 degree contact angle favours speed and radial capacity over pure thrust.

Interchange guidance

Made in England at the plant NSK inherited from RHP, so RHP and NSK designations cross-reference directly. Typical duty is machine-tool spindles, precision grinders, high-speed motion control and instrument spindles.