51103-SKF 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 51103-SKF model number is decoded

The 51100 series order number 51103 is a SKF single-direction thrust ball bearing for a 17 mm seat, built to ISO 104, with a flat housing seating surface, 17×30×9 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 03 decodes to 17 mm 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 17×30×9 mm (0.669×1.181×0.354 in), 6.5 mm radial section, C 11.4 kN, C0 21.2 kN, Pu 0.78 kN. reference speed 8,500 r/min (thermal) and limiting speed 12,000 r/min (mechanical), catalogue mass 25 g. Section proportions: the 6.5 mm radial section compares with 17 mm of bore (section/bore ≈ 0.38) and the 9 mm height is 1.38× that section — the proportions that identify the 51100 envelope at a glance. Pitch-diameter arithmetic: dm = (17+30)/2 = 23.5 mm; at the 12,000 r/min limiting speed that corresponds to roughly 282k mm·r/min, the figure used when comparing cage speed demand across the thrust-ball series. Speed band width for this size is 3,500 r/min between reference and limiting (1.41× ratio); lubrication, preload and heat removal decide where inside that band 51103 can actually run. Rating split for documentation: dynamic 11.4 kN (L10 life), static 21.2 kN (safety factor s0), fatigue limit 0.78 kN (adjusted life) — three different uses of three different numbers for 51103, none interchangeable with another. Washer-annulus check: the π/4·(D²−d²) contact annulus of 51103 covers about 480 mm², distributing C0 21.2 kN over a mean track circle of π·dm ≈ 74 mm. 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 9 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 11.4 kN C.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 17 mm shaft, while the housing washer bore is larger and runs loose; swapping them locks the ball set and burns the tracks.
• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 11.4/21.2 kN and the available 30 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• When the housing seat cannot be machined square to the 17 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.
• 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 9 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• The 11.4/21.2 kN figures belong to 51103 specifically (the single flat pressed steel execution of 51103); suffixed, sphered and counterpart-series order numbers are separate articles, so write the complete designation on the order and the maintenance record.