QJ208 bearing: complete specifications & equivalents
The QJ208 is a ISO 15 radial bearing sized 40 x 80 x 18 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | NTN |
| Bore diameter d | 40 mm |
| Outer diameter D | 80 mm |
| Width B | 18 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 49 kN |
| Basic static load rating C0 | 70.5 kN |
| Fatigue load limit Pu | 3.05 kN |
| Limiting speed (mechanical) | 6900 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 450 g |
| Manufacturer designation | NTN QJ208 |
| 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 & QJ200-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.15 in |
| Width B | 0.709 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 20 mm |
| Smallest bore in QJ200-series | 15 mm |
| Largest outer diameter in QJ200-series | 360 mm |
| Width range across QJ200-series | 11–58 mm |
| Bore position in QJ200-series (smallest first) | 6 of 29 |
| Bore above smallest QJ200-series size | 25 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the QJ208 model number is decoded
At 40 x 80 x 18 mm, NTN QJ208 sits in the medium-duty QJ200 four-point family of the angular-contact programme. NTN builds the number from QJ2 is the four-point dimension series (medium-duty QJ200 four-point family), then the last two digits 08 give the bore by the standard code table (40 mm); there is no suffix — the split inner ring and 35 deg contact angle are inherent to the QJ design. NTN prints 49 kN dynamic and 70.5 kN static for this size and a 3.05 kN fatigue load limit Pu. For a 40 mm shaft with combined load, the practical shortlist is this series, its neighbouring dimension series, and — where thrust reverses — a back-to-back pair rather than a single row. Mount with the thrust against the marked face: the contact angle runs from the low shoulder of the inner ring to the high shoulder of the outer ring, and reversing it throws the capacity away.
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
- 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
- pressed-steel cage pocket wear and rivet loosening after repeated ball skid at light load and high speed
- lubricant starvation scoring at the ball/raceway contact when grease volume or relubrication interval is guessed instead of calculated
- flaking that starts at the raceway shoulder on the thrust-loaded side when axial load repeatedly exceeds the design share
Selection pitfalls — read before you substitute
- In this size class the common miss is lubrication interval, not fit — a 40 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.
- On a 40 mm shaft, an interference fit eats internal clearance; skipping the clearance/preload recalculation is the classic cause of a new bearing running 20 deg C hotter than the drawing suggests.
- The 6,900 r/min speed figure assumes the catalogue lubrication state and a correctly set pair; real limits drop fast with excess grease fill or heavy preload.
- Never use a four-point or double-row bearing as a like-for-like swap for a single QJ208 without re-checking axial float, heat and housing width — the kinematics differ.
- The 49/70.5 kN ratings and 3.05 kN Pu here are NTN Ball and Roller Bearings CAT.No.2203E figures for QJ208; 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 QJ208?
QJ208 is a four-point contact ball bearing to ISO 15: 40 mm bore, 80 mm outside diameter, 18 mm width (1.575 x 3.15 x 0.709 in). From NTN Ball and Roller Bearings CAT.No.2203E: C 49 kN, C0 70.5 kN and a 3.05 kN fatigue load limit Pu; the grease limiting speed is 6,900 r/min and the oil rating 9,200 r/min; mass about 450 g.
How is the QJ208 designation structured?
QJ2 is the four-point dimension series (medium-duty QJ200 four-point family); the last two digits 08 give the bore by the standard code table (40 mm); there is no suffix — the split inner ring and 35 deg contact angle are inherent to the QJ design. The 80 mm OD and 18 mm width follow the ISO 15 boundary-dimension plan for that series.
Which axial direction does QJ208 support?
QJ208 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 QJ208?
Per NTN Ball and Roller Bearings CAT.No.2203E, the grease limiting speed is 6,900 r/min and the oil rating 9,200 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 QJ208?
The 40/80/18 mm envelope is ISO 15 interchangeable, but internal geometry — contact angle, osculation, cage and shoulder details — is maker-specific. Re-verify C 49 kN / C0 70.5 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.