QJ-324-N2MA bearing: complete specifications & equivalents

Specification table

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.

Cross references & equivalents

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-324-N2MA model number is decoded

QJ 324 N2MA is SKF's 120 mm-bore QJ four-point contact ball bearing of the QJ300 series, 120×260×55 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. machined brass cage, outer-ring-centred (suffix MA), which guides on the outer ring rather than on the balls. Envelope 120×260×55 mm (4.724×10.236×2.165 in), 70.0 mm radial section height, C 415 kN, C0 530 kN, Pu 16.3 kN.SKF publishes only the 4,500 r/min limiting speed for this execution, catalogue mass 16000 g. Speed planning distinguishes the two published ceilings mechanically: the cage and balls tolerate 4,500 r/min and no separate thermal reference is published; at dm ≈ 190.0 mm the corresponding dn is approximately 855k mm·r/min. Sizing arithmetic on the 120 mm bore: 415 kN C divided by the 70.0 mm radial section height gives 5.9 kN per section millimetre; the 16000 g mass and 4 % Pu/C share frame the light-load floor for the adjusted-life check. Speed-ratio note for this exact unit: no thermal reference speed is listed (seal/grease life governs), so the 4,500 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

Selection pitfalls — read before you substitute

• Provide a minimum axial load (spring preload is common) so the balls stay correctly seated at speed and light-load conditions; otherwise they skid.
• The inner ring is two-piece: handle both halves together, mount square, and do not separate the split ring unless the fitting procedure requires it.
• The inner ring is two-piece: handle both halves together, mount square, and do not separate the split ring unless the fitting procedure requires it.
• Anti-rotation is built into QJ-324-N2MA: 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 MA brass cage of QJ-324-N2MA is outer-ring-centred: its guide land needs an uninterrupted oil film, so check lubricant reach when the bearing is used purely as a thrust location.
• Catalogue ratings are SKF PUB BU/P1 17000 figures for QJ 324 N2MA as the qj slotted execution; the other order numbers of the QJ 324 size are different products and may carry different ratings — always quote the full designation when purchasing.