51240-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 51240-M model number is decoded

The 51200 series order number 51240 M is a SKF single-direction thrust ball bearing for a 200 mm seat, built to ISO 104, with a flat housing seating surface, 200×280×62 mm boundary dimensions. Three separable parts make the set: the tight-bore shaft washer that locates on the shaft, the loose-bore housing washer in its register, and the ball-cage assembly; load is purely axial and acts in one direction. reading 51xxx as a code: the 1 after 5 identifies one load direction and a flat seat, and the next digit ranks the section 1 (light) to 4 (heavy) before the two-digit bore code. bore code 40 decodes to 200 mm (code 40 × 5) under the same 00/01/02/03-exception, ×5 rule SKF uses across its coded bearing ranges. the trailing M names a solid machined brass window cage centred on the balls rather than on a washer, the catalogue choice when size, speed or interrupted lubrication rules out sheet steel. Envelope 200×280×62 mm (7.874×11.024×2.441 in), 40.0 mm radial section, C 338 kN, C0 1320 kN, Pu 31.5 kN. reference speed 1,100 r/min (thermal) and limiting speed 1,500 r/min (mechanical), catalogue mass 12000 g. Rating split for documentation: dynamic 338 kN (L10 life), static 1320 kN (safety factor s0), fatigue limit 31.5 kN (adjusted life) — three different uses of three different numbers for 51240 M, none interchangeable with another. Sizing arithmetic on the 200 mm bore: 338 kN C over the 40.0 mm radial section gives 8.4 kN per section millimetre, and the 62 mm stack height is 1.55× that section — proportions typical of a 51200 thrust section. Bore-to-OD planning: OD 280 over bore 200 is a 1.40× step for this size, and the 62 mm height gives a bore/height ratio of 3.23; use these ratios when the housing recess around the 200 mm shaft is the first constraint. Speed band width for this size is 400 r/min between reference and limiting (1.36× ratio); lubrication, preload and heat removal decide where inside that band 51240 M can actually run. Envelope economics: the 62 mm axial height over a 40.0 mm radial section yields 5.5 kN of dynamic capacity per height millimetre, and the bearing weighs 12000 g for 338 kN C — about 36 g per rated kN. 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 51240 M adds a small amount of mass and cage strength without changing the 200×280×62 mm ISO 104 envelope, so the pressed-cage execution drops into the same recess but should not be assumed equal under the 1,500 r/min ceiling.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• 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.
• 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 51240 against two-way load lifts the loose washer off its raceway.
• When the housing seat cannot be machined square to the 200 mm shaft, the sphered 53-series execution of this size with its U seat washer is the self-aligning counterpart of this flat 51200 bearing.
• On vertical shafts retain the loose housing washer positively with a cover or ring and verify the grease fill does not drain out of the 62 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• The 338/1320 kN figures belong to 51240 M specifically (the single flat brass execution of 51240); suffixed, sphered and counterpart-series order numbers are separate articles, so write the complete designation on the order and the maintenance record.