QJ-309-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-309-N2MA model number is decoded

QJ 309 N2MA is SKF's 45 mm-bore QJ four-point contact ball bearing of the QJ300 series, 45×100×25 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 45×100×25 mm (1.772×3.937×0.984 in), 27.5 mm radial section height, C 100 kN, C0 83 kN, Pu 3.55 kN.SKF publishes only the 12,000 r/min limiting speed for this execution, catalogue mass 1050 g. Mass and section check: 1050 g inside the 45×100×25 mm outline leaves a 27.5 mm radial section, and the 83 kN static rating is 0.83× the dynamic rating — plan static safety and minimum load against those numbers rather than against sister executions. At the printed limiting speed of 12,000 r/min the mean pitch diameter dm ≈ 72.5 mm implies a dn value around 870k mm·r/min; only the limiting speed is published for this execution. Bore-to-OD planning: OD 100 over bore 45 is a 2.22× step for this size, and the 25 mm width gives a bore/width ratio of 1.80; use these ratios when housing space around the 45 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

• Keep a small axial gap between the outer ring and the cover flange so it can accommodate thermal movement; never clamp the outer ring solid.
• 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.
• The MA machined brass cage is outer-ring-centred — inspect its guide clearance when servicing
• Anti-rotation is built into QJ-309-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-309-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 309 N2MA as the qj slotted execution; the other order numbers of the QJ 309 size are different products and may carry different ratings — always quote the full designation when purchasing.