81138-M bearing: complete specifications & equivalents
The 81138-M is a ISO 104 radial bearing sized 190 x 240 x 37 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 190 mm |
| Outer diameter D | 240 mm |
| Width B | 37 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 310 kN |
| Basic static load rating C0 | 1460 kN |
| Fatigue load limit Pu | 125 kN |
| Reference speed (thermal) | 700 rpm |
| Limiting speed (mechanical) | 1400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 4750 g |
| Manufacturer designation | 81138 M |
| Standard | ISO 104 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 11.1 cylindrical roller thrust bearings |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 11.1 cylindrical roller thrust bearings) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 11.1 cylindrical roller thrust bearings); 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.
Dimensions in inches & 81100-series range
| Bore d | 7.48 in |
|---|---|
| Outer diameter D | 9.449 in |
| Width B | 1.457 in |
| ISO bore code | 38 |
| Radial section height (D−d)/2 | 25 mm |
| Smallest bore in 81100-series | 15 mm |
| Largest outer diameter in 81100-series | 400 mm |
| Width range across 81100-series | 9–63 mm |
| Bore position in 81100-series (smallest first) | 27 of 34 |
| Bore above smallest 81100-series size | 175 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 81138-M model number is decoded
The light 811 series bearing 81138 M carries pure axial load at low to moderate speed: 310 kN dynamic and 1460 kN static across a 190×240 mm washer pair, 37 mm overall height. In 81138 M, 811 fixes the 240 mm OD and 37 mm height; 38 selects the 190 mm seat, and the machined brass M cage is the only execution suffix on these rigid-washer bearings. The bearing takes thrust in one direction only — reverse loads lift the roller set off its track; arrange a mirrored second bearing for reversing duty, and keep the applied load above factor A 0.17. Static safety matters for shock duty: compare peak axial force against C0 1460 kN with the application's static factor, since crane hooks and screw positions see their worst load at zero or low speed. In vertical shafts let the rotor weight provide the minimum load where possible; otherwise fit a spring pack above the housing washer, and verify the washer face is flooded with oil at first start.
Typical equipment & failure modes
Common applications
- rolling-mill screwdown mechanisms and press adjusters
- slewing and turntable pivots with predominantly axial force
- crane hook crossheads carrying pure hook thrust while the hook swivels
- screw jack and lifting screw thrust positions under slow, steady load
Known failure patterns
- roller skidding and raceway glazing once the thrust falls below the catalogue minimum axial load (factor A)
- housing-washer rotation scored into an unmachined or loose seating face
- oil starvation at the sliding contact zones of large spherical roller thrust bearings on forced-feed trips
- false brinelling and rust-red witness marks on standby machines under external vibration
- smearing at roller-raceway contacts during unloaded startup before the oil film or preload is established
Selection pitfalls — read before you substitute
- At 190 mm bore the washers are too stiff to conform to a non-square seat: machine the shoulders parallel or the roller ends concentrate load into a narrow stripe across 37 mm.
- Do not substitute a thrust ball bearing of the same ISO envelope by rating alone: the cylindrical rollers of 81138 M need different minimum load and lubrication despite the shared 190×240 mm outline.
- The separable washers are not interchangeable across series: an 811 and an 812 washer for the same bore differ in OD and height — order WS/GS parts by the full 81138 M size.
- the 700 r/min reference speed is the thermal criterion under load, the 1,400 r/min limiting speed is mechanical and oil lubrication typically raises the usable figure.
- The 310/1460 kN ratings assume flat, full-support washer seats; a housing face narrower than the 240 mm washer OD invalidates the rating through edge stress.
- The 310/1460 kN ratings and 4750 g mass are SKF catalogue values transcribed from ch. 11.1 of PUB BU/P1 17000 (PDF table page 894); mounting data — Ea/Eb raceway diameters and the minimum load factor A — appears in the running text because the structured record carries the boundary envelope only.
Frequently asked questions
How should a 81138 M be mounted?
Interference fit for the shaft washer, sliding fit for the housing washer, full-area square shoulders both sides, press on washer backs only, and shim the cover so the rollers turn freely while the factor-A 0.17 minimum load is present.
What are the dimensions and ratings of the 81138 M?
A 81138 M measures 190 mm bore × 240 mm outside diameter × 37 mm width (7.48 × 9.449 × 1.457 in). From SKF catalogue PUB BU/P1 17000: dynamic C 310 kN, static C0 1460 kN, fatigue limit Pu 125 kN, reference speed 700 r/min, limiting speed 1,400 r/min, mass about 4750 g. Raceway diameters Ea 197 mm / Eb 233 mm and minimum load factor A 0.17 guide the seat design.
How is the 81138 M designation read?
The first three digits 811 give the dimension series (light 811 series); 38 encodes the 190 mm bore (code 38 × 5); the suffix denotes the machined brass M cage. WS and GS washers of the same size can be ordered separately.
Why does 81138 M need a minimum axial load?
Below factor A 0.17 the cylindrical rollers skid instead of rolling, glazing and smearing the washer tracks. Springs, preload shims or rotor weight must keep the thrust above the catalogue minimum, especially during unloaded starts.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 11.1 cylindrical roller thrust bearings on 2026-09-27. Read our editorial & correction policy.