51128 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 51128 model number is decoded

The 51100 series order number 51128 is a SKF single-direction thrust ball bearing for a 140 mm seat, built to ISO 104, with a flat housing seating surface, 140×180×31 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 28 decodes to 140 mm (code 28 × 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 140×180×31 mm (5.512×7.087×1.22 in), 20.0 mm radial section, C 111 kN, C0 440 kN, Pu 12.9 kN. reference speed 1,800 r/min (thermal) and limiting speed 2,600 r/min (mechanical), catalogue mass 2050 g. Stack/annulus proportions: the 31 mm axial stack over the 10,053 mm² washer annulus gives 3.08 mm of height per annular square millimetre ×10⁻³, and at 2050 g the bearing holds about 214.6 kN of C0 per kilogram. Pitch-diameter arithmetic: dm = (140+180)/2 = 160.0 mm; at the 2,600 r/min limiting speed that corresponds to roughly 416k mm·r/min, the figure used when comparing cage speed demand across the thrust-ball series. Section proportions: the 20.0 mm radial section compares with 140 mm of bore (section/bore ≈ 0.14) and the 31 mm height is 1.55× that section — the proportions that identify the 51100 envelope at a glance. Rating split for documentation: dynamic 111 kN (L10 life), static 440 kN (safety factor s0), fatigue limit 12.9 kN (adjusted life) — three different uses of three different numbers for 51128, none interchangeable with another. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 1 at the 2,600 r/min limiting speed raises the required axial preload to about 173.1 kN; the reference-speed value 82.9 kN is the thermal design point. 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. On this 140 mm size the pressed cage and separable washers make the bearing interchangeable across brands on the ISO 104 plan, but the SKF ratings 111/440 kN are this catalogue's figures — confirm the replacement order's ratings rather than swapping on envelope alone.

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 31 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• The 51128 is a pure axial bearing: it must never be subjected to radial load — any radial force on the 140 mm shaft has to be carried by a radial bearing mounted alongside it.
• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 111/440 kN and the available 180 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• 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.
• Catalogue ratings are SKF PUB BU/P1 17000 figures for 51128 as the single flat pressed steel execution; other order numbers of the 51128 size are different products and may carry different ratings or seating geometry — always quote the full designation when purchasing.