51111-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 51111-SKF model number is decoded

The 51100 series order number 51111 is a SKF single-direction thrust ball bearing for a 55 mm seat, built to ISO 104, with a flat housing seating surface, 55×78×16 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 11 decodes to 55 mm (code 11 × 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 55×78×16 mm (2.165×3.071×0.63 in), 11.5 mm radial section, C 30.2 kN, C0 81.5 kN, Pu 3 kN. reference speed 3,800 r/min (thermal) and limiting speed 5,300 r/min (mechanical), catalogue mass 230 g. Light-load floor: Pu = 3 kN is the equivalent-load threshold below which the SKF adjusted-life equation credits very long life for 51111; the number is 10 % of the 30.2 kN dynamic rating. Selection figures for 51111: the C0/C ratio is 2.70, Pu 3 kN is about 10 % of C, and the catalogue mass works out to roughly 4 g per millimetre of bore; the printed minimum-load factor is A 0.039. Mass and section check: 230 g inside the 55×78×16 mm outline leaves a 11.5 mm radial section, and the 81.5 kN static rating is 2.70× the dynamic rating — plan static safety and minimum preload against those figures. Rating split for documentation: dynamic 30.2 kN (L10 life), static 81.5 kN (safety factor s0), fatigue limit 3 kN (adjusted life) — three different uses of three different numbers for 51111, none interchangeable with another. At the printed limiting speed of 5,300 r/min the mean pitch diameter dm ≈ 66.5 mm implies a dn value around 352k mm·r/min; the 3,800 r/min reference speed is the thermal-planning value under catalogue load. 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 16 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 30.2 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 0.039; for 51111 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.
• 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 16 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• When the housing seat cannot be machined square to the 55 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.
• 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 30.2 kN track before first rotation.
• Ordering discipline for 51111: the catalogue page quotes 51111 and its 30.2/81.5 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.