51311-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 51311-SKF model number is decoded

Listed in SKF 17000 chapter 5, 51311 is an ISO 104 single-direction thrust ball bearing, 55 mm bore and 105 mm OD on a flat housing seat, standing 35 mm high before installation. The bearing is delivered as separate, interchangeable parts: a ground-bore shaft washer, a loose-bore housing washer and the ball-cage assembly between them, designed for one axial load direction only. 51xxx breaks down as 5 for thrust ball, 1 for one load direction on a flat seat, a section digit 1–4 light-to-heavy, then the two-digit bore code. reading the ending 11: bore 55 mm (code 11 × 5) for this single-direction size, via the standard exceptions 00/01/02/03 and ×5 above them. no cage suffix means the standard stamped steel retainer — a pressed sheet-metal ball-cage assembly that covers the bulk of the thrust-ball assortment. Envelope 55×105×35 mm (2.165×4.134×1.378 in), 25.0 mm radial section, C 101 kN, C0 224 kN, Pu 8.3 kN. reference speed 2,200 r/min (thermal) and limiting speed 3,200 r/min (mechanical), catalogue mass 1300 g. Load balance: C0 224 kN against C 101 kN gives a 2.22 ratio — thrust ball bearings are chosen on static rating and F_a/C0 far more often than on L10 life, while Pu 8.3 kN enters the adjusted-life check. Speed-ratio note for this exact unit: the reference speed is 2,200 r/min against a 3,200 r/min limiting speed, a reference-to-limit ratio of 0.69. Stack/annulus proportions: the 35 mm axial stack over the 6,283 mm² washer annulus gives 5.57 mm of height per annular square millimetre ×10⁻³, and at 1300 g the bearing holds about 172.3 kN of C0 per kilogram. Pitch-diameter arithmetic: dm = (55+105)/2 = 80.0 mm; at the 3,200 r/min limiting speed that corresponds to roughly 256k mm·r/min, the figure used when comparing cage speed demand across the thrust-ball series. Speed planning separates the two ceilings mechanically: the pressed cage and balls tolerate 3,200 r/min while thermal balance under catalogue load sets the 2,200 r/min reference; at dm ≈ 80.0 mm the corresponding dn is approximately 256k mm·r/min. 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 35 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 101 kN C.

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 35 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• 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.
• The 51311 is a pure axial bearing: it must never be subjected to radial load — any radial force on the 55 mm shaft has to be carried by a radial bearing mounted alongside it.
• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 0.26; for 51311 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.
• Catalogue ratings are SKF PUB BU/P1 17000 figures for 51311 as the single flat pressed steel execution; other order numbers of the 51311 size are different products and may carry different ratings or seating geometry — always quote the full designation when purchasing.