NU324 bearing: complete specifications & equivalents
The NU324 is a ISO 15 radial bearing sized 120 x 260 x 55 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 120 mm |
| Outer diameter D | 260 mm |
| Width B | 55 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | steel |
| Basic dynamic load rating C | 500 kN |
| Basic static load rating C0 | 510 kN |
| Fatigue load limit Pu | 51 kN |
| Limiting speed (mechanical) | 2700 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 12500 g |
| Manufacturer designation | NTN NU324 |
| 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 & NU300-series range
| Bore d | 4.724 in |
|---|---|
| Outer diameter D | 10.236 in |
| Width B | 2.165 in |
| ISO bore code | 24 |
| Radial section height (D−d)/2 | 70 mm |
| Smallest bore in NU300-series | 17 mm |
| Largest outer diameter in NU300-series | 620 mm |
| Width range across NU300-series | 14–109 mm |
| Bore position in NU300-series (smallest first) | 21 of 34 |
| Bore above smallest NU300-series size | 103 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| NU324-ECP | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 120×260×55 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 NU324 model number is decoded
NU324 belongs to the NTN cylindrical roller range in NTN Ball and Roller Bearings CAT.No.2203E: line-contact rollers between ground raceways for a 500 kN dynamic rating in the 120 mm bore. On the NTN nameplate NU states which ring carries the ribs, which determines whether NU324 floats or locates; the numeric remainder is the ISO 15 series and 120 mm bore reference, not a fit or clearance instruction. NTN prints the raceway diameters for this size — Fw 154 mm and Ew 226 mm — the envelope inside the 120/260 mm bore/OD where the rollers actually run. Thermal planning around the 2,700 r/min grease ceiling should include the cage type (a pressed sheet-steel cage) and oil-flow option to 3,200 r/min for continuously high-duty 120 mm positions. Provide axial location with an adjacent locating bearing rather than expecting the float cylindrical set to hold thrust on the 120 mm shaft.
Typical equipment & failure modes
Common applications
- mining SAG/ball-mill drive shafts
- offshore drawworks and winch drums
- heavy press and large gearbox main shafts
- rolling-mill work-roll and backup-roll positions
Known failure patterns
- roller smearing (microwelding) at start-up before the oil film builds under insufficient radial load
- pressed-steel cage pocket wear when rollers skid at light load or too-thin lubricant
- micro-pitting when the EHL film falls below the composite roughness at high specific load
- edge loading from shaft deflection beyond the 3–4 arc-minute alignment limit
- electrical pitting on VFD-driven motor shafts without grounding protection
Selection pitfalls — read before you substitute
- At 120 mm bore, oil-lubricated arrangements toward 3,200 r/min need positive flow and drain design; the 12500 g NU324 ring stores enough heat that grease-only duty needs a careful relubrication calculation.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 500/510 kN pair here belongs to NU324 as printed, not to the bare size.
- Never press either ring through the roller complement when fitting: mounting force goes through the ring faces, or the 260 mm race brinells and releases as vibration within hours.
- The EA high-capacity roller complement changes the load figure versus the basic execution of the same number; the 500/510 kN pair here belongs to NU324 as printed, not to the bare size.
- The NU rib arrangement is not interchangeable with another prefix on the same 120 mm seat: outer ring ribbed, inner ring ribless. Swapping NU for NJ changes axial location behaviour even though the 260×55 mm envelope matches.
- The 500/510 kN ratings, 51 kN Pu and 12500 g mass are NTN Ball and Roller Bearings CAT.No.2203E values for NU324 (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 NU324?
NU324 is an NTN NU single-row cylindrical roller bearing to ISO 15: 120 mm bore, 260 mm OD and 55 mm width (4.724 × 10.236 × 2.165 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 500 kN, C0 510 kN, Pu 51 kN, grease limiting speed 2,700 r/min, oil 3,200 r/min, mass about 12500 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. NU324 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. NU324 is supplied in the standard open execution shown in the table.
Can NU324 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 NU324?
Fw is the inner sub-assembly raceway/roller-set envelope diameter and Ew the outer-ring raceway diameter printed for geometric checks: Fw 154 mm, Ew 226 mm. The nominal bore/OD remain 120/260 mm; Fw/Ew describe the rolling-contact path, and speeds still run to 2,700 r/min grease / 3,200 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.