51324-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 51324-M model number is decoded

51324 M is SKF's 120 mm-bore single-direction thrust ball bearing in the 51300 series to the ISO 104 dimension plan, with a flat housing seating surface, measuring 120×210×70 mm. The separable set comprises a shaft washer (ground bore, tight fit on the shaft), a loose-bore housing washer and one ball-cage assembly, reacting axial force in one direction and carrying no radial load. in the 51xxx designation the first 1 marks a single-direction bearing with a flat housing seating surface; the third digit 1–4 grades the dimension series from the light 511 section through the heavy 514 section. the final two digits 24 encode the bore as 120 mm (code 24 × 5), the standard SKF bore-code rule shared with radial bearings. suffix M identifies a one-piece machined brass cage, ball-centred: the large-size and heavy-section option for higher speeds, shock loads and thin-film lubrication where a pressed cage would distort. Envelope 120×210×70 mm (4.724×8.268×2.756 in), 45.0 mm radial section, C 325 kN, C0 980 kN, Pu 28.5 kN. reference speed 1,100 r/min (thermal) and limiting speed 1,500 r/min (mechanical), catalogue mass 11000 g. Pitch-diameter arithmetic: dm = (120+210)/2 = 165.0 mm; at the 1,500 r/min limiting speed that corresponds to roughly 248k 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 1,100 r/min against a 1,500 r/min limiting speed, a reference-to-limit ratio of 0.73. Envelope economics: the 70 mm axial height over a 45.0 mm radial section yields 4.6 kN of dynamic capacity per height millimetre, and the bearing weighs 11000 g for 325 kN C — about 34 g per rated kN. Light-load floor: Pu = 28.5 kN is the equivalent-load threshold below which the SKF adjusted-life equation credits very long life for 51324 M; the number is 9 % of the 325 kN dynamic rating. Static-first selection data: 980 kN C0 spread across the 70 mm stack gives 14.0 kN of static rating per height millimetre, and the 11000 g mass/C0 ratio is about 11 g per static kN — crane-hook and screw positions are normally sized on these two figures. 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 11000 g the machined brass cage represents a meaningful fraction of total mass; balancing checks on high-speed 120 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

• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 120 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 70 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.
• When the housing seat cannot be machined square to the 120 mm shaft, the sphered 53-series execution of this size with its U seat washer is the self-aligning counterpart of this flat 51300 bearing.
• The 325/980 kN figures belong to 51324 M specifically (the single flat brass execution of 51324); suffixed, sphered and counterpart-series order numbers are separate articles, so write the complete designation on the order and the maintenance record.