51318-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 51318-SKF model number is decoded

The 51300 series order number 51318 is a SKF single-direction thrust ball bearing for a 90 mm seat, built to ISO 104, with a flat housing seating surface, 90×155×50 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 18 decodes to 90 mm (code 18 × 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 90×155×50 mm (3.543×6.102×1.969 in), 32.5 mm radial section, C 182 kN, C0 440 kN, Pu 14.6 kN. reference speed 1,500 r/min (thermal) and limiting speed 2,200 r/min (mechanical), catalogue mass 3800 g. Pitch-diameter arithmetic: dm = (90+155)/2 = 122.5 mm; at the 2,200 r/min limiting speed that corresponds to roughly 270k mm·r/min, the figure used when comparing cage speed demand across the thrust-ball series. Rating split for documentation: dynamic 182 kN (L10 life), static 440 kN (safety factor s0), fatigue limit 14.6 kN (adjusted life) — three different uses of three different numbers for 51318, none interchangeable with another. Section proportions: the 32.5 mm radial section compares with 90 mm of bore (section/bore ≈ 0.36) and the 50 mm height is 1.54× that section — the proportions that identify the 51300 envelope at a glance. Minimum-load arithmetic: with dm ≈ 122.5 mm and factor A 1.3, Fam ≈ A·(n·dm/1000)² at the 1,500 r/min reference speed is about 43.9 kN for 51318; below that preload the balls skid and smear the tracks. Light-load floor: Pu = 14.6 kN is the equivalent-load threshold below which the SKF adjusted-life equation credits very long life for 51318; the number is 8 % of the 182 kN dynamic rating. 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 90 mm size the pressed cage and separable washers make the bearing interchangeable across brands on the ISO 104 plan, but the SKF ratings 182/440 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

• 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.
• When the housing seat cannot be machined square to the 90 mm shaft, the sphered 53-series execution of this size with its U seat washer is the self-aligning counterpart of this flat 51300 bearing.
• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 1.3; for 51318 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.
• The 51318 is a pure axial bearing: it must never be subjected to radial load — any radial force on the 90 mm shaft has to be carried by a radial bearing mounted alongside it.
• The 182/440 kN figures belong to 51318 specifically (the single flat pressed steel execution of 51318); suffixed, sphered and counterpart-series order numbers are separate articles, so write the complete designation on the order and the maintenance record.