7221B bearing: complete specifications & equivalents
The 7221B is a ISO 15 radial bearing sized 105 x 190 x 36 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 105 mm |
| Outer diameter D | 190 mm |
| Width B | 36 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel, stamped ribbon (J-type) |
| Basic dynamic load rating C | 157 kN |
| Basic static load rating C0 | 129 kN |
| Fatigue load limit Pu | 8.05 kN |
| Limiting speed (mechanical) | 3200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3870 g |
| Manufacturer designation | NTN 7221B |
| 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 | 4.134 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 1.417 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 42.5 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) | 22 of 36 |
| Bore above smallest 7200-series size | 95 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 7221B | ISO 15 | full Dimensions and internal design equivalent — standard interchange. | ISO 15 boundary-dimension envelope; standard interchange — confirm clearance class and precision with the supplier. |
Interchange levels: full standard interchange · partial verify parameters · verify manual confirmation required. Links resolve to the equivalent model's specification page where available.
How the 7221B model number is decoded
The medium-duty 7200 single-row family entry 7221B carries a 105 mm bore in a 190 mm outside diameter, 36 mm wide envelope. Reading the code: 72 is the single-row dimension series (medium-duty 7200 single-row family), 21 encodes the 105 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 40 deg contact angle is the lever that turns the 129 kN static rating into useful one-direction thrust capacity. Selection starts from the thrust share: as axial load grows past roughly half the radial load, an angular-contact position of this section usually outlives a deep-groove one. Set preload or end-play with the pair as a unit and lock the adjustment; a single angular-contact bearing cannot run free like a deep-groove one.
Typical equipment & failure modes
Common applications
- rolling-mill and metalworking drive shafts
- large pump, fan and compressor rotor shafts
- crane and hoist gearbox shafts
- paper-machine roll and calendar drives
Known failure patterns
- impact brinelling dents on the 30 deg contact path after a shaft-side hammer blow during mounting, because axial shock travels straight through the contact angle
- loss of preload after housing-fret or shaft creep, leaving the pair loose — ball skidding, cage rattle and a falling natural frequency follow
- resin-cage cracking on the 7900-series sizes after hot, dry running or solvent attack on the polymer
- contamination-induced denting — hard particles rolled into the contact ellipse become the initiation points for surface fatigue
- edge loading and early spalling from housing bores that are out of round or shoulders that are too small for the ring face
Selection pitfalls — read before you substitute
- Bearings of 105 mm bore arrive heavy enough that handling damage (dents from slings, tilting on the shaft) is a real failure precursor — use proper lifting and heating kit.
- 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.
- Never use a four-point or double-row bearing as a like-for-like swap for a single 7221B without re-checking axial float, heat and housing width — the kinematics differ.
- The 3,200 r/min speed figure assumes the catalogue lubrication state and a correctly set pair; real limits drop fast with excess grease fill or heavy preload.
- A 7221B mounted the wrong way round still turns smoothly by hand; the failure shows up weeks later as raceway flaking on the unloaded-looking side.
- The 157/129 kN ratings and 8.05 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 7221B; 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 7221B?
7221B is a single-row angular contact ball bearing to ISO 15: 105 mm bore, 190 mm outside diameter, 36 mm width (4.134 x 7.48 x 1.417 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 157 kN, C0 129 kN and a 8.05 kN fatigue load limit Pu; the grease limiting speed is 3,200 r/min and the oil rating 4,300 r/min; mass about 3870 g.
How is the 7221B designation structured?
72 is the single-row dimension series (medium-duty 7200 single-row family); 21 encodes the 105 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 190 mm OD and 36 mm width follow the ISO 15 boundary-dimension plan for that series.
Which axial direction does 7221B support?
One 7221B 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 7221B?
Per NTN Ball and Roller Bearings CAT.No.2203E, the grease limiting speed is 3,200 r/min and the oil rating 4,300 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 7221B?
The 105/190/36 mm envelope is ISO 15 interchangeable, but internal geometry — contact angle, osculation, cage and shoulder details — is maker-specific. Re-verify C 157 kN / C0 129 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.