51420-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 51420-M model number is decoded

The 51400 series order number 51420 M is a SKF single-direction thrust ball bearing for a 100 mm seat, built to ISO 104, with a flat housing seating surface, 100×210×85 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 20 decodes to 100 mm (code 20 × 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 100×210×85 mm (3.937×8.268×3.346 in), 55.0 mm radial section, C 371 kN, C0 1060 kN, Pu 31.5 kN. reference speed 950 r/min (thermal) and limiting speed 1,400 r/min (mechanical), catalogue mass 15000 g. Selection figures for 51420 M: the C0/C ratio is 2.86, Pu 31.5 kN is about 8 % of C, and the catalogue mass works out to roughly 150 g per millimetre of bore; the printed minimum-load factor is A 5.8. Capacity density: 371 kN C from 15.000 kg of bearing steel gives about 24.7 kN per kilogram; static density is correspondingly 70.7 kN/kg at C0 1060 kN. Minimum-load arithmetic: with dm ≈ 155.0 mm and factor A 5.8, Fam ≈ A·(n·dm/1000)² at the 950 r/min reference speed is about 125.8 kN for 51420 M; below that preload the balls skid and smear the tracks. Sizing arithmetic on the 100 mm bore: 371 kN C over the 55.0 mm radial section gives 6.7 kN per section millimetre, and the 85 mm stack height is 1.55× that section — proportions typical of a 51400 thrust section. Stack/annulus proportions: the 85 mm axial stack over the 26,782 mm² washer annulus gives 3.17 mm of height per annular square millimetre ×10⁻³, and at 15000 g the bearing holds about 70.7 kN of C0 per kilogram. 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 15000 g the machined brass cage represents a meaningful fraction of total mass; balancing checks on high-speed 100 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

• When the housing seat cannot be machined square to the 100 mm shaft, the sphered 53-series execution of this size with its U seat washer is the self-aligning counterpart of this flat 51400 bearing.
• 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 85 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.
• Keep the applied thrust above Fam ≈ A·(n·dm/1000)² with the printed factor A 5.8; for 51420 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.
• Ordering discipline for 51420: the catalogue page quotes 51420 M and its 371/1060 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.