NSKSuper-Precision Angular Contact Ball Bearing 55x100x21 mm 15° Contact Angle ABEC 7

Product Description

What this part is

An NSK 7211CTYP4 super-precision single-row angular contact ball bearing, 55 mm bore by 100 mm outside diameter by 21 mm width. It is a spindle-grade bearing for machine tools, grinding heads, high-speed gearboxes and precision rotary equipment.

Decoding the designation

7211 — single-row angular contact ball bearing, 55 x 100 x 21 mm, 72-series sectionC — 15° contact angle in the NSK schemeP4 — ABEC 7 precision class

What these specs mean in practice

The 15° contact angle is the high-speed end of the super-precision range. A shallower angle puts more of the ball load radially and less axially, which reduces centrifugal loading on the ball-to-raceway contact and lowers heat generation at speed. Grinding spindles, high-rpm milling heads and any spindle whose limit is thermal rather than structural use 15° for exactly that reason.

The trade-off is thrust: a 15° bearing carries substantially less axial load and offers lower axial stiffness than a 25° or 30° bearing of the same envelope. Where the cut generates heavy axial force, the steeper angle is the correct specification.

ABEC 7 holds bore, outside diameter and running accuracy to super-precision limits. That is what allows a spindle built on these bearings to hold runout to a few microns, and it is only realised if the shaft and housing seats are machined to a comparable standard.

Published specifications

Bore: 55 mmOutside diameter: 100 mmWidth: 21 mmRows: 1Contact angle: 15°Precision class: ABEC 7 / ISO P4Closure: openRolling elements: steel balls

Quantity and configuration

This listing supplies one bearing. It carries no matched-set or preload designation, so it is supplied as a single bearing rather than as half of a ground pair. Spacer rings, lock nuts and housings are not included.

Fitting notes

The high shoulder on the outer ring marks the contact angle direction, which sets the arrangement when more than one bearing is used. Back-to-back carries moment load and is the usual spindle configuration; face-to-face tolerates slight misalignment; tandem doubles thrust capacity in one direction. Mounting pressure goes on the ring faces rather than through the balls, and shaft and housing seats held to matching roundness and cylindricity limits are what preserve the ABEC 7 accuracy.

Interchange guidance

Genuine equivalents are 7211-envelope super-precision bearings at 15° and P4 class from other makers, such as SKF 7211 CD/P4A, FAG B7211C.TPA.P4, RHP 7211CTP4 and Fafnir 2MM211WI. The 7211A5 at 25°, 7211A at 30° and 7211B at 40° share the same 55 x 100 x 21 mm envelope but are different parts — they change spindle stiffness and thrust capacity. Bearings of this envelope at P0 or P5 class are also a specification change.