51236-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 51236-M model number is decoded

The 51200 series order number 51236 M is a SKF single-direction thrust ball bearing for a 180 mm seat, built to ISO 104, with a flat housing seating surface, 180×250×56 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 36 decodes to 180 mm (code 36 × 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 180×250×56 mm (7.087×9.843×2.205 in), 35.0 mm radial section, C 302 kN, C0 1120 kN, Pu 28.5 kN. reference speed 1,200 r/min (thermal) and limiting speed 1,600 r/min (mechanical), catalogue mass 8600 g. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 6.1 at the 1,600 r/min limiting speed raises the required axial preload to about 721.8 kN; the reference-speed value 406.0 kN is the thermal design point. Envelope economics: the 56 mm axial height over a 35.0 mm radial section yields 5.4 kN of dynamic capacity per height millimetre, and the bearing weighs 8600 g for 302 kN C — about 28 g per rated kN. Speed band width for this size is 400 r/min between reference and limiting (1.33× ratio); lubrication, preload and heat removal decide where inside that band 51236 M can actually run. Capacity density: 302 kN C from 8.600 kg of bearing steel gives about 35.1 kN per kilogram; static density is correspondingly 130.2 kN/kg at C0 1120 kN. Track-circle loading: per millimetre of mean track circumference the 302 kN dynamic rating corresponds to roughly 0.45 kN/mm of π·dm track, a useful comparison against the other dimension series of the 180 mm bore. 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 8600 g the machined brass cage represents a meaningful fraction of total mass; balancing checks on high-speed 180 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

• 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 56 mm stack; thrust-ball bearings on horizontal shafts should have the shaft washer (the tight one) against the rotating element.
• 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 302 kN track before first rotation.
• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 302/1120 kN and the available 250 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• 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 51236 against two-way load lifts the loose washer off its raceway.
• Catalogue ratings are SKF PUB BU/P1 17000 figures for 51236 M as the single flat brass execution; other order numbers of the 51236 size are different products and may carry different ratings or seating geometry — always quote the full designation when purchasing.