51408-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 51408-SKF model number is decoded

Listed in SKF 17000 chapter 5, 51408 is an ISO 104 single-direction thrust ball bearing, 40 mm bore and 90 mm OD on a flat housing seat, standing 36 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 08: bore 40 mm (code 08 × 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 40×90×36 mm (1.575×3.543×1.417 in), 25.0 mm radial section, C 95.6 kN, C0 183 kN, Pu 6.8 kN. reference speed 2,400 r/min (thermal) and limiting speed 3,400 r/min (mechanical), catalogue mass 1100 g. Stack/annulus proportions: the 36 mm axial stack over the 5,105 mm² washer annulus gives 7.05 mm of height per annular square millimetre ×10⁻³, and at 1100 g the bearing holds about 166.4 kN of C0 per kilogram. Speed band width for this size is 1,000 r/min between reference and limiting (1.42× ratio); lubrication, preload and heat removal decide where inside that band 51408 can actually run. Imperial cross-check for procurement drawings: 1.575 in bore, 3.543 in OD, 1.417 in height, and the 1100 g catalogue mass converts to 1.100 kg (38.8 oz). Rating split for documentation: dynamic 95.6 kN (L10 life), static 183 kN (safety factor s0), fatigue limit 6.8 kN (adjusted life) — three different uses of three different numbers for 51408, none interchangeable with another. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 0.26 at the 3,400 r/min limiting speed raises the required axial preload to about 12.7 kN; the reference-speed value 6.3 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 40 mm size the pressed cage and separable washers make the bearing interchangeable across brands on the ISO 104 plan, but the SKF ratings 95.6/183 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 36 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 51408 is a pure axial bearing: it must never be subjected to radial load — any radial force on the 40 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 51408 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 51408 as the single flat pressed steel execution; other order numbers of the 51408 size are different products and may carry different ratings or seating geometry — always quote the full designation when purchasing.