51424-M bearing: complete specifications & equivalents

Specification table

Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018)) · extracted 2026-09-28

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 51424-M model number is decoded

Listed in SKF 17000 chapter 5, 51424 M is an ISO 104 single-direction thrust ball bearing, 120 mm bore and 250 mm OD on a flat housing seat, standing 102 mm high before installation. The bearing is delivered as separate, interchangeable parts: a ground-bore shaft washer, a loose-bore housing washer and the ball-cage assembly between them, designed for one axial load direction only. 51xxx breaks down as 5 for thrust ball, 1 for one load direction on a flat seat, a section digit 1–4 light-to-heavy, then the two-digit bore code. reading the ending 24: bore 120 mm (code 24 × 5) for this single-direction size, via the standard exceptions 00/01/02/03 and ×5 above them. M-cage execution: brass machined from solid and ball-centred, giving heavier guidance than the standard pressed retainer at the top end of the thrust-ball range. Envelope 120×250×102 mm (4.724×9.843×4.016 in), 65.0 mm radial section, C 432 kN, C0 1320 kN, Pu 36 kN. reference speed 800 r/min (thermal) and limiting speed 1,100 r/min (mechanical), catalogue mass 25500 g. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 16 at the 1,100 r/min limiting speed raises the required axial preload to about 662.6 kN; the reference-speed value 350.5 kN is the thermal design point. Load balance: C0 1320 kN against C 432 kN gives a 3.06 ratio — thrust ball bearings are chosen on static rating and F_a/C0 far more often than on L10 life, while Pu 36 kN enters the adjusted-life check. Bore-to-OD planning: OD 250 over bore 120 is a 2.08× step for this size, and the 102 mm height gives a bore/height ratio of 1.18; use these ratios when the housing recess around the 120 mm shaft is the first constraint. Minimum-load arithmetic: with dm ≈ 185.0 mm and factor A 16, Fam ≈ A·(n·dm/1000)² at the 800 r/min reference speed is about 350.5 kN for 51424 M; below that preload the balls skid and smear the tracks. Sizing arithmetic on the 120 mm bore: 432 kN C over the 65.0 mm radial section gives 6.6 kN per section millimetre, and the 102 mm stack height is 1.57× that section — proportions typical of a 51400 thrust section. Machined-cage order-number note: the M brass cage is a one-piece ball-centred window cage, chosen at the heavy end of the section for speed and shock duty; it is heavier and stiffer than the pressed-steel execution of the smaller sizes and tolerates interrupted lubrication far better, which is why the catalogue restricts the M suffix to the large bores. The M cage of 51424 M adds a small amount of mass and cage strength without changing the 120×250×102 mm ISO 104 envelope, so the pressed-cage execution drops into the same recess but should not be assumed equal under the 1,100 r/min ceiling.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 16; for 51424 M a spring preload or the rotor weight is part of the selection at light load and high speed, because unloaded balls skid rather than roll.
• A 51-series bearing reacts thrust in one direction only — reversing positions need a mirrored single-direction pair or a 52-series double-direction unit; fitting a single 51424 against two-way load lifts the loose washer off its raceway.
• The 51424 M is a pure axial bearing: it must never be subjected to radial load — any radial force on the 120 mm shaft has to be carried by a radial bearing mounted alongside it.
• The three components are separable and interchangeable within the ISO 104 size, but keep this bearing's parts together in service and never combine washers from different manufacturers or a worn washer with a new ball set.
• Ordering discipline for 51424: the catalogue page quotes 51424 M and its 432/1320 kN ratings as one exact article; bare-number substitutions from another series or brand need a fresh dimension and rating check, not a like-for-like assumption.