QJ-304-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-304-N2MA model number is decoded

QJ 304 N2MA is SKF's 20 mm-bore QJ four-point contact ball bearing of the QJ300 series, 20×52×15 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 20×52×15 mm (0.787×2.047×0.591 in), 16.0 mm radial section height, C 32 kN, C0 21.6 kN, Pu 0.93 kN.SKF publishes only the 24,000 r/min limiting speed for this execution, catalogue mass 180 g. Selection figures for QJ 304 N2MA: the static-to-dynamic ratio C0/C is 0.68, Pu 0.93 kN is about 3 % of C, and catalogue mass works out to roughly 9 g per millimetre of bore. Envelope economics: the 15 mm width over a 16.0 mm section yields 0.94 mm of ring width per section millimetre, and the bearing weighs 180 g for 32 kN of dynamic capacity — about 6 g per rated kN. Bore-to-OD planning: OD 52 over bore 20 is a 2.60× step for this size, and the 15 mm width gives a bore/width ratio of 1.33; use these ratios when housing space around the 20 mm shaft is the first constraint. 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

• 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.
• Run the QJ as a thrust bearing with radial clearance in the housing, paired with a separate radial bearing; the QJ outer ring must not be radially clamped.
• Anti-rotation is built into QJ-304-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-304-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 304 N2MA as the qj slotted execution; the other order numbers of the QJ 304 size are different products and may carry different ratings — always quote the full designation when purchasing.