7324B bearing: complete specifications & equivalents
The 7324B 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 | brass |
| Basic dynamic load rating C | 249 kN |
| Basic static load rating C0 | 231 kN |
| Fatigue load limit Pu | 13.1 kN |
| Limiting speed (mechanical) | 2500 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 14700 g |
| Manufacturer designation | NTN 7324B |
| 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 & 7300-series range
| Bore d | 4.724 in |
|---|---|
| Outer diameter D | 10.236 in |
| Width B | 2.165 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 70 mm |
| Smallest bore in 7300-series | 10 mm |
| Largest outer diameter in 7300-series | 420 mm |
| Width range across 7300-series | 11–80 mm |
| Bore position in 7300-series (smallest first) | 24 of 32 |
| Bore above smallest 7300-series size | 110 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 7324B | 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 7324B model number is decoded
The heavy-duty 7300 single-row family entry 7324B carries a 120 mm bore in a 260 mm outside diameter, 55 mm wide envelope. The designation breaks down as 73 is the single-row dimension series (heavy-duty 7300 single-row family); 24 encodes the 120 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 3,300 r/min sits 800 r/min above the 2,500 r/min grease figure — a 1.32x 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. Heat-mounting to 80-90 deg C is the clean route onto a 120 mm shaft; drive-fits through the balls transmit force through the contact ellipse and can brinell it.
Typical equipment & failure modes
Common applications
- crusher and mill pinion shafts
- large pump and turbine auxiliary shafts
- steel-plant conveyor and table roll drives
- wind-turbine and heavy-machinery auxiliaries
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
- thermal runaway from excessive preload: the pair runs hot, grease darkens and the contact ellipse spreads until the raceways smear
- resin-cage cracking on the 7900-series sizes after hot, dry running or solvent attack on the polymer
- flaking that starts at the raceway shoulder on the thrust-loaded side when axial load repeatedly exceeds the design share
- lubricant starvation scoring at the ball/raceway contact when grease volume or relubrication interval is guessed instead of calculated
Selection pitfalls — read before you substitute
- At this size the shaft fit, shoulder geometry and preload procedure dominate the outcome; a 120 mm bore bearing forgives nothing in a poorly machined housing.
- 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.
- If the application vibrates at standstill (transport, idle machine next to a running line), specify protection: the contact ellipse of a preloaded bearing false-brinells faster than a loose one.
- Grease rated for deep-groove motor duty is not automatically right at 2,500 r/min with preload; check the grease speed factor against the catalogue figure.
- Grease rated for deep-groove motor duty is not automatically right at 2,500 r/min with preload; check the grease speed factor against the catalogue figure.
- The 249/231 kN ratings and 13.1 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for 7324B; 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 7324B?
7324B is a single-row angular contact ball bearing to ISO 15: 120 mm bore, 260 mm outside diameter, 55 mm width (4.724 x 10.236 x 2.165 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 249 kN, C0 231 kN and a 13.1 kN fatigue load limit Pu; the grease limiting speed is 2,500 r/min and the oil rating 3,300 r/min; mass about 14700 g.
How is the 7324B designation structured?
73 is the single-row dimension series (heavy-duty 7300 single-row family); 24 encodes the 120 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 260 mm OD and 55 mm width follow the ISO 15 boundary-dimension plan for that series.
Which axial direction does 7324B support?
One 7324B 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 7324B?
Per NTN Ball and Roller Bearings CAT.No.2203E, the grease limiting speed is 2,500 r/min and the oil rating 3,300 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 7324B?
The 120/260/55 mm envelope is ISO 15 interchangeable, but internal geometry — contact angle, osculation, cage and shoulder details — is maker-specific. Re-verify C 249 kN / C0 231 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.