51326-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 51326-M model number is decoded

The 51300 series order number 51326 M is a SKF single-direction thrust ball bearing for a 130 mm seat, built to ISO 104, with a flat housing seating surface, 130×225×75 mm boundary dimensions. Three separable parts make the set: the tight-bore shaft washer that locates on the shaft, the loose-bore housing washer in its register, and the ball-cage assembly; load is purely axial and acts in one direction. reading 51xxx as a code: the 1 after 5 identifies one load direction and a flat seat, and the next digit ranks the section 1 (light) to 4 (heavy) before the two-digit bore code. bore code 26 decodes to 130 mm (code 26 × 5) under the same 00/01/02/03-exception, ×5 rule SKF uses across its coded bearing ranges. the trailing M names a solid machined brass window cage centred on the balls rather than on a washer, the catalogue choice when size, speed or interrupted lubrication rules out sheet steel. Envelope 130×225×75 mm (5.118×8.858×2.953 in), 47.5 mm radial section, C 358 kN, C0 1140 kN, Pu 32 kN. reference speed 1,000 r/min (thermal) and limiting speed 1,400 r/min (mechanical), catalogue mass 13000 g. Load balance: C0 1140 kN against C 358 kN gives a 3.18 ratio — thrust ball bearings are chosen on static rating and F_a/C0 far more often than on L10 life, while Pu 32 kN enters the adjusted-life check. At the printed limiting speed of 1,400 r/min the mean pitch diameter dm ≈ 177.5 mm implies a dn value around 249k mm·r/min; the 1,000 r/min reference speed is the thermal-planning value under catalogue load. Sizing arithmetic on the 130 mm bore: 358 kN C over the 47.5 mm radial section gives 7.5 kN per section millimetre, and the 75 mm stack height is 1.58× that section — proportions typical of a 51300 thrust section. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 6.8 at the 1,400 r/min limiting speed raises the required axial preload to about 419.9 kN; the reference-speed value 214.2 kN is the thermal design point. Bore-to-OD planning: OD 225 over bore 130 is a 1.73× step for this size, and the 75 mm height gives a bore/height ratio of 1.73; use these ratios when the housing recess around the 130 mm shaft is the first constraint. 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 13000 g the machined brass cage represents a meaningful fraction of total mass; balancing checks on high-speed 130 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 6.8; for 51326 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 51326 M is a pure axial bearing: it must never be subjected to radial load — any radial force on the 130 mm shaft has to be carried by a radial bearing mounted alongside it.
• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 358/1140 kN and the available 225 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 130 mm shaft, while the housing washer bore is larger and runs loose; swapping them locks the ball set and burns the tracks.
• Ordering discipline for 51326: the catalogue page quotes 51326 M and its 358/1140 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.