51148-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 51148-M model number is decoded

51148 M is SKF's 240 mm-bore single-direction thrust ball bearing in the 51100 series to the ISO 104 dimension plan, with a flat housing seating surface, measuring 240×300×45 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 48 encode the bore as 240 mm (code 48 × 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 240×300×45 mm (9.449×11.811×1.772 in), 30.0 mm radial section, C 234 kN, C0 1040 kN, Pu 23.6 kN. reference speed 1,100 r/min (thermal) and limiting speed 1,600 r/min (mechanical), catalogue mass 7550 g. Imperial cross-check for procurement drawings: 9.449 in bore, 11.811 in OD, 1.772 in height, and the 7550 g catalogue mass converts to 7.550 kg (266.3 oz). Washer-annulus check: the π/4·(D²−d²) contact annulus of 51148 M covers about 25,447 mm², distributing C0 1040 kN over a mean track circle of π·dm ≈ 848 mm. Speed planning separates the two ceilings mechanically: the pressed brass cage and balls tolerate 1,600 r/min while thermal balance under catalogue load sets the 1,100 r/min reference; at dm ≈ 270.0 mm the corresponding dn is approximately 432k mm·r/min. Speed band width for this size is 500 r/min between reference and limiting (1.45× ratio); lubrication, preload and heat removal decide where inside that band 51148 M can actually run. Static-first selection data: 1040 kN C0 spread across the 45 mm stack gives 23.1 kN of static rating per height millimetre, and the 7550 g mass/C0 ratio is about 7 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. The M cage of 51148 M adds a small amount of mass and cage strength without changing the 240×300×45 mm ISO 104 envelope, so the pressed-cage execution drops into the same recess but should not be assumed equal under the 1,600 r/min ceiling.

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 5.6; for 51148 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 51148 M is a pure axial bearing: it must never be subjected to radial load — any radial force on the 240 mm shaft has to be carried by a radial bearing mounted alongside it.
• 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.
• Identify the washers before fitting: the shaft washer has the ground, smaller bore and takes an interference fit on the 240 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 51148: the catalogue page quotes 51148 M and its 234/1040 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.