QJ-308-N2PHAS bearing: complete specifications & equivalents
The QJ-308-N2PHAS is a ISO 15 radial bearing sized 40 x 90 x 23 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 40 mm |
| Outer diameter D | 90 mm |
| Width B | 23 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer |
| Basic dynamic load rating C | 78 kN |
| Basic static load rating C0 | 64 kN |
| Fatigue load limit Pu | 2.7 kN |
| Limiting speed (mechanical) | 14000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 780 g |
| Manufacturer designation | QJ 308 N2PHAS |
| Standard | ISO 15 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018) |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018)); SKF® and SKF Explorer® are trademarks of AB SKF, used here for identification only — mpnbase is not an authorized SKF distributor. Boundary dimensions are ISO 15 interchangeable; current production values may differ, verify at skf.com.
Dimensions in inches & QJ300-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 3.543 in |
| Width B | 0.906 in |
| ISO bore code | — |
| Radial section height (D−d)/2 | 25 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) | 6 of 27 |
| Bore above smallest QJ300-series size | 23 mm |
Cross references & equivalents
| Equivalent model | Brand | Match level | Note |
|---|---|---|---|
| 7308-BE-2RZP | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope, but catalogue C/C0 differ between executions (78/64 kN vs 46.2/30.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 7308-BEP | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope, but catalogue C/C0 differ between executions (78/64 kN vs 46.2/30.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 7308-BECBP | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope, but catalogue C/C0 differ between executions (78/64 kN vs 50/32.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 7308-BEGAPH | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope, but catalogue C/C0 differ between executions (78/64 kN vs 50/32.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 7308-BECBM | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope, but catalogue C/C0 differ between executions (78/64 kN vs 50/32.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 7308-BECBY | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope, but catalogue C/C0 differ between executions (78/64 kN vs 53/35.5 kN) — boundary dimensions match, not a load-rating equivalent. |
| 7308-ACCBM | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | Same 40×90×23 mm envelope, but catalogue C/C0 differ between executions (78/64 kN vs 56/36 kN) — boundary dimensions match, not a load-rating equivalent. |
| QJ-308-N2MA | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 40×90×23 mm envelope with catalogue ratings within 10 %; QJ 308 N2MA is the brass cage, open arrangement, four-point split-inner-ring execution of this size — boundary dimensions interchangeable, execution differs. |
| QJ-308-MA | SKF | full Dimensions and internal design equivalent — standard interchange. | Same 40×90×23 mm envelope with catalogue ratings within 10 %; QJ 308 MA is the brass cage, open arrangement, four-point split-inner-ring execution of this size — boundary dimensions interchangeable, execution differs. |
| 7308 | SKF | partial Main dimensions match; tolerances, seals or internal clearance differ. | SKF SKF 7308 BEP shares the 40×90×23 mm angular-contact envelope, but catalogue C/C0 differ (78/64 kN vs 46.2/30.5 kN) — envelope match, not a load-rating equivalent. |
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 QJ-308-N2PHAS model number is decoded
QJ 308 N2PHAS is SKF's 40 mm-bore QJ four-point contact ball bearing of the QJ300 series, 40×90×23 mm, with a two-piece inner ring for bidirectional axial location beside a radial bearing. QJ identifies a four-point contact ball bearing with a two-piece inner ring: the gothic-arch raceways seat each ball at four points, giving axial location in both directions while a paired radial bearing carries the radial load. N2 marks two locating slots, 180° apart, in one outer-ring side face: pins or dogs engage the slots to stop the outer ring turning in its radially-clear housing bore. glass-fibre reinforced PEEK cage, outer-ring-centred with lubrication grooves in the guiding surfaces (suffix PHAS), for very high-speed oil-air or grease lubrication. Envelope 40×90×23 mm (1.575×3.543×0.906 in), 25.0 mm radial section height, C 78 kN, C0 64 kN, Pu 2.7 kN.SKF publishes only the 14,000 r/min limiting speed for this execution, catalogue mass 780 g. At the printed limiting speed of 14,000 r/min the mean pitch diameter dm ≈ 65.0 mm implies a dn value around 910k mm·r/min; only the limiting speed is published for this execution. The 2.7 kN fatigue load limit is the equivalent-load floor for long-life adjustment; with 78/64 kN ratings and 780 g mass this execution carries about 1.95 kN of C per millimetre of bore. Speed-ratio note for this exact unit: no thermal reference speed is listed (seal/grease life governs), so the 14,000 r/min limiting value is the single published ceiling. Locating-slot execution: the two N2 notches are milled into one outer-ring side face exactly 180 degrees apart and engaged by housing dogs or headed pins during assembly; verify dog engagement by hand before the cover goes on, deburr the slot edges after any housing rework, and re-inspect the slot roots for fretting marks at each overhaul because a dog that rides only one slot lets the outer ring walk. The slots identify this order number unmistakably: the plain MA/PHAS execution of the same bore has no notches and must be secured differently.
Typical equipment & failure modes
Common applications
- clutch and brake assemblies
- textile machinery traverse drives
- gearbox shafts where one QJ locates axially in both directions beside a radial bearing
Known failure patterns
- axial over-travel when the outer ring is clamped instead of left with radial clearance and a small end-play gap
- two-piece inner-ring separation damage if the split ring is pressed or heated unevenly during mounting
- locating-slot root fretting or dog wear when only one N2 notch carries the anti-rotation torque
- edge loading from shaft deflection or housing misalignment
- mounting score marks when the bearing is cocked over a burr or keyway
Selection pitfalls — read before you substitute
- Engage the N2 slots with housing dogs at assembly — a radially loose outer ring without positive anti-rotation creeps its seat
- Provide a minimum axial load (spring preload is common) so the balls stay correctly seated at speed and light-load conditions; otherwise they skid.
- Apply the Fa/Fr ≥ 1,27 condition: at lower ratios the balls contact both sides of a raceway, increasing friction and shortening life — the paired radial bearing should carry the radial share.
- Anti-rotation is built into QJ-308-N2PHAS: check the two N2 slot faces and the engaging housing dogs at every refit, and never rely on cover friction to stop the radially loose outer ring.
- The PHAS PEEK cage of QJ-308-N2PHAS is outer-ring-centred with lubrication grooves: feed clean oil-air or appropriate grease to the guide land and inspect groove filling at overhaul.
- Catalogue ratings are SKF PUB BU/P1 17000 figures for QJ 308 N2PHAS as the qj slotted execution; the other order numbers of the QJ 308 size are different products and may carry different ratings — always quote the full designation when purchasing.
Frequently asked questions
What are the dimensions and catalogue data of QJ-308-N2PHAS?
QJ 308 N2PHAS measures 40 mm bore × 90 mm OD × 23 mm width (1.575 × 3.543 × 0.906 in), mass about 780 g. SKF 17000 ratings: C 78 kN, C0 64 kN, Pu 2.7 kN, SKF publishes only the 14,000 r/min limiting speed for this execution.
What does the N2PHAS suffix mean?
QJ identifies a four-point contact ball bearing with a two-piece inner ring: the gothic-arch raceways seat each ball at four points, giving axial location in both directions while a paired radial bearing carries the radial load. N2 marks two locating slots, 180° apart, in one outer-ring side face: pins or dogs engage the slots to stop the outer ring turning in its radially-clear housing bore. glass-fibre reinforced PEEK cage, outer-ring-centred with lubrication grooves in the guiding surfaces (suffix PHAS), for very high-speed oil-air or grease lubrication.
What minimum axial load does QJ-308-N2PHAS require?
Like angular-contact bearings the QJ needs a minimum axial load to keep the balls seated — spring preload against the outer ring is typical — and the load ratio Fa/Fr ≥ 1,27 keeps contact on one inner-ring raceway and the opposite outer-ring side.
How is a QJ four-point bearing mounted?
As a thrust/locating bearing with radial clearance in the housing, paired with a separate radial bearing (commonly a cylindrical roller bearing): the QJ locates the shaft axially in both directions, the radial bearing carries radial load. Keep the outer ring unclamped with a small end-play gap; N2 slot executions use dogs to stop the outer ring turning.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018) on 2026-09-27. Read our editorial & correction policy.