7211B bearing: complete specifications & equivalents
The 7211B is a ISO 15 radial bearing sized 55 x 100 x 21 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 55 mm |
| Outer diameter D | 100 mm |
| Width B | 21 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 51.5 kN |
| Basic static load rating C0 | 36 kN |
| Fatigue load limit Pu | 2.74 kN |
| Limiting speed (mechanical) | 6100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 612 g |
| Manufacturer designation | NTN 7211B |
| Standard | ISO 15 |
| Catalog version | NTN Ball and Roller Bearings CAT.No.2203E |
| Last verified | 2026-10-01 |
Source: catalog reference (NTN Ball and Roller Bearings CAT.No.2203E) · extracted 2026-10-01
Parameters extracted from the official NTN Ball and Roller Bearings catalogue (NTN Ball and Roller Bearings CAT.No.2203E); NTN® is a trademark of NTN Corporation, used here for identification only — mpnbase is not an authorized NTN distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at ntnglobal.com.
Dimensions in inches & 7200-series range
| Bore d | 2.165 in |
|---|---|
| Outer diameter D | 3.937 in |
| Width B | 0.827 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 22.5 mm |
| Smallest bore in 7200-series | 10 mm |
| Largest outer diameter in 7200-series | 540 mm |
| Width range across 7200-series | 9–85 mm |
| Bore position in 7200-series (smallest first) | 12 of 36 |
| Bore above smallest 7200-series size | 45 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 7211B model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, 7211B appears as a medium-duty 7200 single-row family bearing of 55 mm bore, 100 mm outside diameter and 21 mm width. Two fields make up the code — 72 is the single-row dimension series (medium-duty 7200 single-row family) and 11 encodes the 55 mm bore (bore code x 5), and the trailing B marks the 40 deg contact-angle execution (the no-letter standard bearing works at 30 deg). The oil rating of 8,200 r/min sits 2,100 r/min above the 6,100 r/min grease figure — a 1.34x step that says how much headroom oil cooling buys. When axial load reverses, specify the bearing as a matched pair (DB, DF or DT) instead of two random singles — the catalogue right-hand columns give the paired ratings for exactly this reason. Shaft and housing shoulders must clear the ring corners yet support enough face — the catalogue abutment diameters for the 55 mm bore give the working limits.
Typical equipment & failure modes
Common applications
- gearbox input shafts under helical-gear thrust
- electric motor shafts with axial locating duty
- conveyor drive and tension-drum shafts
- agricultural gearbox and PTO shaft supports
Known failure patterns
- false brinelling on the raceway contact ellipses when a preloaded spindle sits vibrating at standstill — visible as evenly spaced flute-like wear at ball pitch
- thermal runaway from excessive preload: the pair runs hot, grease darkens and the contact ellipse spreads until the raceways smear
- machined-cage land scoring when a high-speed spindle runs past its grease rating and the cage runs dry on its guidance surface
- flaking that starts at the raceway shoulder on the thrust-loaded side when axial load repeatedly exceeds the design share
- contamination-induced denting — hard particles rolled into the contact ellipse become the initiation points for surface fatigue
Selection pitfalls — read before you substitute
- In this size class the common miss is lubrication interval, not fit — a 55 mm spindle at the catalogue speeds needs a calculated relubrication plan, not a calendar one.
- The 40 deg B-execution raises axial capacity but lowers the speed ceiling — do not copy the standard-bearing speed and preload settings onto it.
- Grease rated for deep-groove motor duty is not automatically right at 6,100 r/min with preload; check the grease speed factor against the catalogue figure.
- Do not pair two random 7211B bearings from stock and expect catalogue paired ratings — matched-set grinding is what makes DB/DF/DT preload behave, and NTN sells those as separate order numbers.
- Grease rated for deep-groove motor duty is not automatically right at 6,100 r/min with preload; check the grease speed factor against the catalogue figure.
- The 51.5/36 kN ratings and 2.74 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 7211B; internal geometry legitimately differs between manufacturers, so re-verify ratings, contact angle and suffix before substituting another make on a rated drive.
Frequently asked questions
What are the dimensions and catalogue ratings of NTN 7211B?
7211B is a single-row angular contact ball bearing to ISO 15: 55 mm bore, 100 mm outside diameter, 21 mm width (2.165 x 3.937 x 0.827 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 51.5 kN, C0 36 kN and a 2.74 kN fatigue load limit Pu; the grease limiting speed is 6,100 r/min and the oil rating 8,200 r/min; mass about 612 g.
How is the 7211B designation structured?
72 is the single-row dimension series (medium-duty 7200 single-row family); 11 encodes the 55 mm bore (bore code x 5), and the trailing B marks the 40 deg contact-angle execution (the no-letter standard bearing works at 30 deg). The 100 mm OD and 21 mm width follow the ISO 15 boundary-dimension plan for that series.
Which axial direction does 7211B support?
One 7211B alone takes thrust in one direction only, along its 40 deg contact angle; reversing thrust calls for a second bearing or a factory-matched DB/DF/DT pair (the catalogue right-hand columns list the paired ratings). Radial load is always carried as a combined load through the angled contact.
What lubrication speeds does NTN print for 7211B?
Per NTN Ball and Roller Bearings CAT.No.2203E, the grease limiting speed is 6,100 r/min and the oil rating 8,200 r/min. These are catalogue ceilings for a correctly mounted bearing with the stated lubricant; preload, fill quantity, ambient heat and paired arrangements all move the real limit.
What should be checked before substituting another make for 7211B?
The 55/100/21 mm envelope is ISO 15 interchangeable, but internal geometry — contact angle, osculation, cage and shoulder details — is maker-specific. Re-verify C 51.5 kN / C0 36 kN, the speed figures, contact angle and suffix meaning against the donor catalogue before swapping on a rated drive.
Reviewed & verified by the MPN Base engineering desk against source catalog NTN Ball and Roller Bearings CAT.No.2203E on 2026-10-01. Read our editorial & correction policy.