51124 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 51124 model number is decoded

The 51100 series order number 51124 is a SKF single-direction thrust ball bearing for a 120 mm seat, built to ISO 104, with a flat housing seating surface, 120×155×25 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 120×155×25 mm (4.724×6.102×0.984 in), 17.5 mm radial section, C 85.2 kN, C0 305 kN, Pu 9.65 kN. reference speed 2,200 r/min (thermal) and limiting speed 3,000 r/min (mechanical), catalogue mass 1150 g. Track-circle loading: per millimetre of mean track circumference the 85.2 kN dynamic rating corresponds to roughly 0.20 kN/mm of π·dm track, a useful comparison against the other dimension series of the 120 mm bore. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 0.58 at the 3,000 r/min limiting speed raises the required axial preload to about 98.7 kN; the reference-speed value 53.1 kN is the thermal design point. Speed band width for this size is 800 r/min between reference and limiting (1.36× ratio); lubrication, preload and heat removal decide where inside that band 51124 can actually run. Load balance: C0 305 kN against C 85.2 kN gives a 3.58 ratio — thrust ball bearings are chosen on static rating and F_a/C0 far more often than on L10 life, while Pu 9.65 kN enters the adjusted-life check. Speed-ratio note for this exact unit: the reference speed is 2,200 r/min against a 3,000 r/min limiting speed, a reference-to-limit ratio of 0.73. 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 25 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 85.2 kN C.

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 0.58; for 51124 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.
• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 120 mm shaft, while the housing washer bore is larger and runs loose; swapping them locks the ball set and burns the tracks.
• 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 51100 bearing.
• The 51124 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.
• Ordering discipline for 51124: the catalogue page quotes 51124 and its 85.2/305 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.