51104-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 51104-SKF model number is decoded

Listed in SKF 17000 chapter 5, 51104 is an ISO 104 single-direction thrust ball bearing, 20 mm bore and 35 mm OD on a flat housing seat, standing 10 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 04: bore 20 mm (code 04 × 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 20×35×10 mm (0.787×1.378×0.394 in), 7.5 mm radial section, C 15.1 kN, C0 29 kN, Pu 1.08 kN. reference speed 7,500 r/min (thermal) and limiting speed 10,000 r/min (mechanical), catalogue mass 37 g. Speed planning separates the two ceilings mechanically: the pressed cage and balls tolerate 10,000 r/min while thermal balance under catalogue load sets the 7,500 r/min reference; at dm ≈ 27.5 mm the corresponding dn is approximately 275k mm·r/min. Section proportions: the 7.5 mm radial section compares with 20 mm of bore (section/bore ≈ 0.38) and the 10 mm height is 1.33× that section — the proportions that identify the 51100 envelope at a glance. Envelope economics: the 10 mm axial height over a 7.5 mm radial section yields 1.5 kN of dynamic capacity per height millimetre, and the bearing weighs 37 g for 15.1 kN C — about 2 g per rated kN. Light-load floor: Pu = 1.08 kN is the equivalent-load threshold below which the SKF adjusted-life equation credits very long life for 51104; the number is 7 % of the 15.1 kN dynamic rating. Static-first selection data: 29 kN C0 spread across the 10 mm stack gives 2.9 kN of static rating per height millimetre, and the 37 g mass/C0 ratio is about 1 g per static kN — crane-hook and screw positions are normally sized on these two figures. 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 20 mm size the pressed cage and separable washers make the bearing interchangeable across brands on the ISO 104 plan, but the SKF ratings 15.1/29 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

• 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 15.1 kN track before first rotation.
• 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 10 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• A 51-series bearing reacts thrust in one direction only — reversing positions need a mirrored single-direction pair or a 52-series double-direction unit; fitting a single 51104 against two-way load lifts the loose washer off its raceway.
• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 15.1/29 kN and the available 35 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• The 15.1/29 kN figures belong to 51104 specifically (the single flat pressed steel execution of 51104); suffixed, sphered and counterpart-series order numbers are separate articles, so write the complete designation on the order and the maintenance record.