NU221 bearing: complete specifications & equivalents
The NU221 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 |
| Basic dynamic load rating C | 223 kN |
| Basic static load rating C0 | 241 kN |
| Fatigue load limit Pu | 26.1 kN |
| Limiting speed (mechanical) | 3600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 3870 g |
| Manufacturer designation | NTN NU221 |
| 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 & NU200-series range
| Bore d | 4.134 in |
|---|---|
| Outer diameter D | 7.48 in |
| Width B | 1.417 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 42.5 mm |
| Smallest bore in NU200-series | 15 mm |
| Largest outer diameter in NU200-series | 580 mm |
| Width range across NU200-series | 11–92 mm |
| Bore position in NU200-series (smallest first) | 20 of 36 |
| Bore above smallest NU200-series size | 90 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NU221-ECP | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 105×190×36 mm envelope per ISO 15; catalogue load ratings differ by >10% — re-rate the application before substituting. |
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 NU221 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, NU221 appears as a 105 mm bore single-row cylindrical roller bearing (223 kN C / 241 kN C0) with a pressed sheet-steel cage, listed to the ISO 15 boundary plan. The leading NU defines the rib arrangement (outer ring ribbed, inner ring ribless); the dimension-series digits and the two-digit bore code resolve to 105 mm, with 190 mm OD and 36 mm width from the ISO 15 general plan. The separable ring comes off without removing the roller assembly from the other ring, which eases inspection and lets the non-locating arrangement accommodate thermal shaft growth — the NU design floats on both sides. Mass 3870 g for the 105×190×36 mm NU221 execution covers the pressed-steel cage and full roller complement; substitute on mass plus rating, not envelope alone. Heat the inner ring to max 120 °C for the 105 mm interference fit and support the ring face square during fitting; cocking over a keyway brinells the raceway before first rotation.
Typical equipment & failure modes
Common applications
- cement and mining conveyor drive pulleys
- heavy industrial gearbox and reducer shafts
- large pump, turbine and compressor rotors
- rolling-mill auxiliary drive shafts
Known failure patterns
- roller smearing (microwelding) at start-up before the oil film builds under insufficient radial load
- cage wear accelerated when the EA high-capacity roller complement runs continuously above its thermal balance
- roller-end and raceway scoring from inadequate oil flow under heavy radial load
- false brinelling on standby machines exposed to external vibration
- hard-particle indentation of raceways in unfiltered oil or open arrangements
Selection pitfalls — read before you substitute
- Induction-heat the 105 mm inner ring (max 120 °C) and mount it before fitting the outer ring; the ring mass makes square guidance essential — driving through the rollers brinells the 190 mm raceway.
- Minimum radial load is frequently missed in oversized motor and fan selections: an underloaded NU221 skids at 3,600 r/min and fails by smearing long before L10 fatigue.
- Wide (22/23) and light (10/49) executions at 105 mm bore share bore but not OD/width; check the full NU200 series code before substituting, because housing and shoulder geometry will not interchange.
- If the shaft must be located both ways, do not use NU221 alone: pair it with a locating bearing or specify the NUP execution with the matching loose rib ring from the 2203E table.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 223/241 kN pair here belongs to NU221 as printed, not to the bare size.
- The 223/241 kN ratings, 26.1 kN Pu and 3870 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NU221 (standard execution); other makes sharing the ISO 15 envelope revise internal geometry without changing the order number, so keep the 2203E reference with the specification for critical drives.
Frequently asked questions
What are the dimensions and catalogue data of NU221?
NU221 is an NTN NU single-row cylindrical roller bearing to ISO 15: 105 mm bore, 190 mm OD and 36 mm width (4.134 × 7.48 × 1.417 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 223 kN, C0 241 kN, Pu 26.1 kN, grease limiting speed 3,600 r/min, oil 4,300 r/min, mass about 3870 g. It is open, with a pressed sheet-steel cage.
What is the difference between NU, NJ, NUP, N and NF cylindrical roller bearings?
The prefix states the rib arrangement: NU has two outer-ring ribs and a ribless inner ring (float, no axial load); NJ adds ribs for one-direction location; NUP adds a loose L-ring to locate both directions; N has two inner-ring ribs and a separable outer ring; NF has one rib per ring for one-direction guidance. NU221 is two integral ribs on the outer ring and a ribless, separable inner ring — a non-locating bearing that lets the shaft float axially.
What do the EA, E and ＊ suffixes mean on NTN cylindrical roller bearings?
EA is NTN's high-capacity design with a pressed sheet-steel cage and optimised roller complement in the same ISO 15 envelope; E marks the high-capacity design at the larger bores; the ＊ symbol printed before the code in the NTN catalogue marks the ULTAGE new-generation specification and is not typed as part of the order number. NU221 is supplied in the standard open execution shown in the table.
Can NU221 take axial load and locate a shaft?
the NU design carries no axial load and floats axially on both sides. Provide axial location with an adjacent locating bearing (angular-contact, deep-groove or a paired NJ/NUP set).
What do Fw and Ew mean for NU221?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 126.8 mm, Ew 168.8 mm. The nominal bore/OD remain 105/190 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 3,600 r/min grease / 4,300 r/min oil.
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.