51320-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 51320-SKF model number is decoded

The 51300 series order number 51320 is a SKF single-direction thrust ball bearing for a 100 mm seat, built to ISO 104, with a flat housing seating surface, 100×170×55 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 20 decodes to 100 mm (code 20 × 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 100×170×55 mm (3.937×6.693×2.165 in), 35.0 mm radial section, C 225 kN, C0 570 kN, Pu 18.3 kN. reference speed 1,400 r/min (thermal) and limiting speed 1,900 r/min (mechanical), catalogue mass 4950 g. Imperial cross-check for procurement drawings: 3.937 in bore, 6.693 in OD, 2.165 in height, and the 4950 g catalogue mass converts to 4.950 kg (174.6 oz). Section proportions: the 35.0 mm radial section compares with 100 mm of bore (section/bore ≈ 0.35) and the 55 mm height is 1.57× that section — the proportions that identify the 51300 envelope at a glance. Rating split for documentation: dynamic 225 kN (L10 life), static 570 kN (safety factor s0), fatigue limit 18.3 kN (adjusted life) — three different uses of three different numbers for 51320, none interchangeable with another. Bore-to-OD planning: OD 170 over bore 100 is a 1.70× step for this size, and the 55 mm height gives a bore/height ratio of 1.82; use these ratios when the housing recess around the 100 mm shaft is the first constraint. Stack/annulus proportions: the 55 mm axial stack over the 14,844 mm² washer annulus gives 3.71 mm of height per annular square millimetre ×10⁻³, and at 4950 g the bearing holds about 115.2 kN of C0 per kilogram. 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 100 mm size the pressed cage and separable washers make the bearing interchangeable across brands on the ISO 104 plan, but the SKF ratings 225/570 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

• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 1.9; for 51320 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 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 100 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.
• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 225/570 kN and the available 170 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• Ordering discipline for 51320: the catalogue page quotes 51320 and its 225/570 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.