51252-M 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 51252-M model number is decoded

Listed in SKF 17000 chapter 5, 51252 M is an ISO 104 single-direction thrust ball bearing, 260 mm bore and 360 mm OD on a flat housing seat, standing 79 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 52: bore 260 mm (code 52 × 5) for this single-direction size, via the standard exceptions 00/01/02/03 and ×5 above them. M-cage execution: brass machined from solid and ball-centred, giving heavier guidance than the standard pressed retainer at the top end of the thrust-ball range. Envelope 260×360×79 mm (10.236×14.173×3.11 in), 50.0 mm radial section, C 488 kN, C0 2240 kN, Pu 46.5 kN. reference speed 750 r/min (thermal) and limiting speed 1,100 r/min (mechanical), catalogue mass 25000 g. Pitch-diameter arithmetic: dm = (260+360)/2 = 310.0 mm; at the 1,100 r/min limiting speed that corresponds to roughly 341k mm·r/min, the figure used when comparing cage speed demand across the thrust-ball series. Speed-ratio note for this exact unit: the reference speed is 750 r/min against a 1,100 r/min limiting speed, a reference-to-limit ratio of 0.68. Sizing arithmetic on the 260 mm bore: 488 kN C over the 50.0 mm radial section gives 9.8 kN per section millimetre, and the 79 mm stack height is 1.58× that section — proportions typical of a 51200 thrust section. Light-load floor: Pu = 46.5 kN is the equivalent-load threshold below which the SKF adjusted-life equation credits very long life for 51252 M; the number is 10 % of the 488 kN dynamic rating. Speed planning separates the two ceilings mechanically: the pressed brass cage and balls tolerate 1,100 r/min while thermal balance under catalogue load sets the 750 r/min reference; at dm ≈ 310.0 mm the corresponding dn is approximately 341k mm·r/min. Machined-cage order-number note: the M brass cage is a one-piece ball-centred window cage, chosen at the heavy end of the section for speed and shock duty; it is heavier and stiffer than the pressed-steel execution of the smaller sizes and tolerates interrupted lubrication far better, which is why the catalogue restricts the M suffix to the large bores. At 25000 g the machined brass cage represents a meaningful fraction of total mass; balancing checks on high-speed 260 mm vertical shafts should use the actual M-execution weight, not the lighter pressed-cage catalogue value.

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 24; for 51252 M 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 third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 488/2240 kN and the available 360 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• The 51252 M is a pure axial bearing: it must never be subjected to radial load — any radial force on the 260 mm shaft has to be carried by a radial bearing mounted alongside it.
• 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 79 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• Ordering discipline for 51252: the catalogue page quotes 51252 M and its 488/2240 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.