QJ324 bearing: complete specifications & equivalents
The QJ324 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 | 360 kN |
| Basic static load rating C0 | 765 kN |
| Fatigue load limit Pu | 23.8 kN |
| Limiting speed (mechanical) | 2100 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 15900 g |
| Manufacturer designation | NTN QJ324 |
| 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 & QJ300-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 QJ300-series | 17 mm |
| Largest outer diameter in QJ300-series | 400 mm |
| Width range across QJ300-series | 14–78 mm |
| Bore position in QJ300-series (smallest first) | 21 of 28 |
| Bore above smallest QJ300-series size | 103 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| QJ324 | 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 QJ324 model number is decoded
In NTN Ball and Roller Bearings CAT.No.2203E, QJ324 appears as a heavy-duty QJ300 four-point family bearing of 120 mm bore, 260 mm outside diameter and 55 mm width. Decoding QJ324: QJ3 is the four-point dimension series (heavy-duty QJ300 four-point family), with the last two digits 24 give the bore by the standard code table (120 mm); there is no suffix — the split inner ring and 35 deg contact angle are inherent to the QJ design. The radial section height here is 70.0 mm, and the catalogue couples that with C 360 kN / C0 765 kN. 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. Grease quantity matters as much as grade at 2,100 r/min: fill about a third of the free space and let the bearing purge on first run.
Typical equipment & failure modes
Common applications
- large pump and turbine auxiliary shafts
- steel-plant conveyor and table roll drives
- wind-turbine and heavy-machinery auxiliaries
- heavy industrial gearbox main shafts
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
- loss of preload after housing-fret or shaft creep, leaving the pair loose — ball skidding, cage rattle and a falling natural frequency follow
- machined-cage land scoring when a high-speed spindle runs past its grease rating and the cage runs dry on its guidance surface
- edge loading and early spalling from housing bores that are out of round or shoulders that are too small for the ring face
- current-erosion pitting on VFD-driven motor shafts, first visible as a grey frosted band across both raceways
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 QJ split inner ring must be clamped by the shaft nut/shoulder on both halves — assembling it against a single small shoulder leaves one half-ring free to walk.
- Do not pair two random QJ324 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.
- The C0 of 765 kN is a static rating, not a permissible running thrust — sizing continuous axial load from C0 alone is a recurring drawing-office error.
- A single-row angular contact left loose on the shaft to "help assembly" will fret the seat: the contact angle keeps driving the ring axially under load.
- The 360/765 kN ratings and 23.8 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for QJ324; 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 QJ324?
QJ324 is a four-point 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 360 kN, C0 765 kN and a 23.8 kN fatigue load limit Pu; the grease limiting speed is 2,100 r/min and the oil rating 2,800 r/min; mass about 15900 g.
How is the QJ324 designation structured?
QJ3 is the four-point dimension series (heavy-duty QJ300 four-point family); the last two digits 24 give the bore by the standard code table (120 mm); there is no suffix — the split inner ring and 35 deg contact angle are inherent to the QJ design. The 260 mm OD and 55 mm width follow the ISO 15 boundary-dimension plan for that series.
Which axial direction does QJ324 support?
QJ324 is a four-point contact bearing: the split inner ring lets each ball touch the raceways at two points, so one bearing locates the shaft in both axial directions at its 35 deg contact angle. It is normally mounted with slight radial clearance against the housing as the axial-locating member.
What lubrication speeds does NTN print for QJ324?
Per NTN Ball and Roller Bearings CAT.No.2203E, the grease limiting speed is 2,100 r/min and the oil rating 2,800 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 QJ324?
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 360 kN / C0 765 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.