51217-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 51217-SKF model number is decoded

Listed in SKF 17000 chapter 5, 51217 is an ISO 104 single-direction thrust ball bearing, 85 mm bore and 125 mm OD on a flat housing seat, standing 31 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 17: bore 85 mm (code 17 × 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 85×125×31 mm (3.346×4.921×1.22 in), 20.0 mm radial section, C 97.5 kN, C0 275 kN, Pu 9.8 kN. reference speed 2,200 r/min (thermal) and limiting speed 3,000 r/min (mechanical), catalogue mass 1200 g. Washer-annulus check: the π/4·(D²−d²) contact annulus of 51217 covers about 6,597 mm², distributing C0 275 kN over a mean track circle of π·dm ≈ 330 mm. Load balance: C0 275 kN against C 97.5 kN gives a 2.82 ratio — thrust ball bearings are chosen on static rating and F_a/C0 far more often than on L10 life, while Pu 9.8 kN enters the adjusted-life check. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 0.39 at the 3,000 r/min limiting speed raises the required axial preload to about 38.7 kN; the reference-speed value 20.8 kN is the thermal design point. Capacity density: 97.5 kN C from 1.200 kg of bearing steel gives about 81.3 kN per kilogram; static density is correspondingly 229.2 kN/kg at C0 275 kN. Track-circle loading: per millimetre of mean track circumference the 97.5 kN dynamic rating corresponds to roughly 0.30 kN/mm of π·dm track, a useful comparison against the other dimension series of the 85 mm bore. 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 31 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 97.5 kN C.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• When the housing seat cannot be machined square to the 85 mm shaft, the sphered 53-series execution of this size with its U seat washer is the self-aligning counterpart of this flat 51200 bearing.
• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 85 mm shaft, while the housing washer bore is larger and runs loose; swapping them locks the ball set and burns the tracks.
• 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 31 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.
• Ordering discipline for 51217: the catalogue page quotes 51217 and its 97.5/275 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.