51224 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 51224 model number is decoded

The 51200 series order number 51224 is a SKF single-direction thrust ball bearing for a 120 mm seat, built to ISO 104, with a flat housing seating surface, 120×170×39 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 24 decodes to 120 mm (code 24 × 5) under the same 00/01/02/03-exception, ×5 rule SKF uses across its coded bearing ranges. the suffix-free listing carries the catalogue default: a pressed (stamped sheet-steel) ball-cage assembly, light and quiet, used across the small and medium sizes. Envelope 120×170×39 mm (4.724×6.693×1.535 in), 25.0 mm radial section, C 127 kN, C0 390 kN, Pu 11.8 kN. reference speed 1,600 r/min (thermal) and limiting speed 2,200 r/min (mechanical), catalogue mass 2650 g. Rating split for documentation: dynamic 127 kN (L10 life), static 390 kN (safety factor s0), fatigue limit 11.8 kN (adjusted life) — three different uses of three different numbers for 51224, none interchangeable with another. Speed-ratio note for this exact unit: the reference speed is 1,600 r/min against a 2,200 r/min limiting speed, a reference-to-limit ratio of 0.73. Capacity density: 127 kN C from 2.650 kg of bearing steel gives about 47.9 kN per kilogram; static density is correspondingly 147.2 kN/kg at C0 390 kN. Minimum-load arithmetic: with dm ≈ 145.0 mm and factor A 1, Fam ≈ A·(n·dm/1000)² at the 1,600 r/min reference speed is about 53.8 kN for 51224; below that preload the balls skid and smear the tracks. Track-circle loading: per millimetre of mean track circumference the 127 kN dynamic rating corresponds to roughly 0.28 kN/mm of π·dm track, a useful comparison against the other dimension series of the 120 mm bore. Execution note for this order number: the flat housing seating surface must be machined square to the shaft axis and supported across the full washer face — unlike the sphered 53-series execution this pressed-cage 51-series bearing has no self-aligning capability at all, so seat squareness is checked at mounting, not compensated in service. Inspection after removal of a 39 mm-high stack means checking both washer faces: the loose housing washer often shows the first false-brinell marks under machine vibration even though the tight shaft washer carries the rotating load of 127 kN C.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• 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 39 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 1; for 51224 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.
• When the housing seat cannot be machined square to the 120 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.
• Heat the shaft washer to at most 120 °C for mounting, or press it via a sleeve on its ground bore — force applied through the housing washer or the ball set brinells the 127 kN track before first rotation.
• Catalogue ratings are SKF PUB BU/P1 17000 figures for 51224 as the single flat pressed steel execution; other order numbers of the 51224 size are different products and may carry different ratings or seating geometry — always quote the full designation when purchasing.