QJ311 bearing: complete specifications & equivalents
The QJ311 is a ISO 15 radial bearing sized 55 x 120 x 29 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 55 mm |
| Outer diameter D | 120 mm |
| Width B | 29 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 118 kN |
| Basic static load rating C0 | 170 kN |
| Fatigue load limit Pu | 7.3 kN |
| Limiting speed (mechanical) | 4600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1760 g |
| Manufacturer designation | NTN QJ311 |
| 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 | 2.165 in |
|---|---|
| Outer diameter D | 4.724 in |
| Width B | 1.142 in |
| ISO bore code | 11 |
| Radial section height (D−d)/2 | 32.5 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) | 9 of 28 |
| Bore above smallest QJ300-series size | 38 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| QJ311 | 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 QJ311 model number is decoded
NTN QJ311 belongs to the heavy-duty QJ300 four-point family: the catalogue boundary dimensions read 55 / 120 / 29 mm (bore / OD / width). Decoding QJ311: QJ3 is the four-point dimension series (heavy-duty QJ300 four-point family), with the last two digits 11 give the bore by the standard code table (55 mm); there is no suffix — the split inner ring and 35 deg contact angle are inherent to the QJ design. Catalogue dynamic rating C is 118 kN against C0 170 kN — a C0/C ratio of 1.44 that is typical of an angular-contact contact ellipse. Where the same envelope must also be sealed, or where mounting mistakes are likely, compare with the double-row 52/53 catalogue pages before fixing the bill of materials. Heat-mounting to 80-90 deg C is the clean route onto a 55 mm shaft; drive-fits through the balls transmit force through the contact ellipse and can brinell it.
Typical equipment & failure modes
Common applications
- conveyor drive and tension-drum shafts
- agricultural gearbox and PTO shaft supports
- printing-press cylinder and folder shafts
- machine-tool spindle cartridges and driven tooling
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
- resin-cage cracking on the 7900-series sizes after hot, dry running or solvent attack on the polymer
- lubricant starvation scoring at the ball/raceway contact when grease volume or relubrication interval is guessed instead of calculated
- current-erosion pitting on VFD-driven motor shafts, first visible as a grey frosted band across both raceways
Selection pitfalls — read before you substitute
- In this size class the common miss is lubrication interval, not fit — a 55 mm spindle at the catalogue speeds needs a calculated relubrication plan, not a calendar one.
- 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.
- The C0 of 170 kN is a static rating, not a permissible running thrust — sizing continuous axial load from C0 alone is a recurring drawing-office error.
- Never use a four-point or double-row bearing as a like-for-like swap for a single QJ311 without re-checking axial float, heat and housing width — the kinematics differ.
- Substituting the B (40 deg) execution for the standard 30 deg bearing changes the axial/radial load split — the shaft position and the mating bearing see different forces even though the envelope is identical.
- The 118/170 kN ratings and 7.3 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for QJ311; 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 QJ311?
QJ311 is a four-point contact ball bearing to ISO 15: 55 mm bore, 120 mm outside diameter, 29 mm width (2.165 x 4.724 x 1.142 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 118 kN, C0 170 kN and a 7.3 kN fatigue load limit Pu; the grease limiting speed is 4,600 r/min and the oil rating 6,100 r/min; mass about 1760 g.
How is the QJ311 designation structured?
QJ3 is the four-point dimension series (heavy-duty QJ300 four-point family); the last two digits 11 give the bore by the standard code table (55 mm); there is no suffix — the split inner ring and 35 deg contact angle are inherent to the QJ design. The 120 mm OD and 29 mm width follow the ISO 15 boundary-dimension plan for that series.
Which axial direction does QJ311 support?
QJ311 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 QJ311?
Per NTN Ball and Roller Bearings CAT.No.2203E, the grease limiting speed is 4,600 r/min and the oil rating 6,100 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 QJ311?
The 55/120/29 mm envelope is ISO 15 interchangeable, but internal geometry — contact angle, osculation, cage and shoulder details — is maker-specific. Re-verify C 118 kN / C0 170 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.