51138-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 51138-M model number is decoded

The 51100 series order number 51138 M is a SKF single-direction thrust ball bearing for a 190 mm seat, built to ISO 104, with a flat housing seating surface, 190×240×37 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 38 decodes to 190 mm (code 38 × 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 190×240×37 mm (7.48×9.449×1.457 in), 25.0 mm radial section, C 172 kN, C0 710 kN, Pu 18 kN. reference speed 1,400 r/min (thermal) and limiting speed 2,000 r/min (mechanical), catalogue mass 4050 g. Mass and section check: 4050 g inside the 190×240×37 mm outline leaves a 25.0 mm radial section, and the 710 kN static rating is 4.13× the dynamic rating — plan static safety and minimum preload against those figures. Pitch-diameter arithmetic: dm = (190+240)/2 = 215.0 mm; at the 2,000 r/min limiting speed that corresponds to roughly 430k mm·r/min, the figure used when comparing cage speed demand across the thrust-ball series. Selection figures for 51138 M: the C0/C ratio is 4.13, Pu 18 kN is about 10 % of C, and the catalogue mass works out to roughly 21 g per millimetre of bore; the printed minimum-load factor is A 2.6. Load balance: C0 710 kN against C 172 kN gives a 4.13 ratio — thrust ball bearings are chosen on static rating and F_a/C0 far more often than on L10 life, while Pu 18 kN enters the adjusted-life check. Preload at the mechanical ceiling: repeating Fam ≈ A·(n·dm/1000)² with factor A 2.6 at the 2,000 r/min limiting speed raises the required axial preload to about 480.7 kN; the reference-speed value 235.6 kN is the thermal design point. 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 51138 M adds a small amount of mass and cage strength without changing the 190×240×37 mm ISO 104 envelope, so the pressed-cage execution drops into the same recess but should not be assumed equal under the 2,000 r/min ceiling.

Typical equipment & failure modes

Selection pitfalls — read before you substitute

• 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 2.6; for 51138 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.
• When the housing seat cannot be machined square to the 190 mm shaft, the sphered 53-series execution of this size with its U seat washer is the self-aligning counterpart of this flat 51100 bearing.
• The third digit grades the section: 511 light, then 512, 513 and 514 progressively taller and heavier at the same bore — select from 172/710 kN and the available 240 mm OD, never substitute a lighter series for a heavier one without rechecking C and C0.
• The 172/710 kN figures belong to 51138 M specifically (the single flat brass execution of 51138); suffixed, sphered and counterpart-series order numbers are separate articles, so write the complete designation on the order and the maintenance record.