81238-M bearing: complete specifications & equivalents
The 81238-M is a ISO 104 radial bearing sized 190 x 270 x 62 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 | 270 mm |
| Width B | 62 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 695 kN |
| Basic static load rating C0 | 2900 kN |
| Fatigue load limit Pu | 250 kN |
| Reference speed (thermal) | 500 rpm |
| Limiting speed (mechanical) | 1000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 12000 g |
| Manufacturer designation | 81238 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 & 81200-series range
| Bore d | 7.48 in |
|---|---|
| Outer diameter D | 10.63 in |
| Width B | 2.441 in |
| ISO bore code | 38 |
| Radial section height (D−d)/2 | 40 mm |
| Smallest bore in 81200-series | 30 mm |
| Largest outer diameter in 81200-series | 420 mm |
| Width range across 81200-series | 16–95 mm |
| Bore position in 81200-series (smallest first) | 23 of 28 |
| Bore above smallest 81200-series size | 160 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 81238-M model number is decoded
81238 M is a single-direction cylindrical roller thrust bearing to ISO 104 in the heavy 812 series: a flat shaft washer, a roller-and-cage set and a housing washer stacked to 190×270×62 mm, listed in SKF catalogue PUB BU/P1 17000 ch. 11.1. Reading the code: the first three digits 812 give the dimension series (heavy 812 series), the last two 38 encode the 190 mm shaft washer bore (code 38 × 5), and M names the cage execution. Small sizes ship with machined brass M cages to guide heavy rollers at the lubricant limit; the 695 kN rating assumes oil or grease reaching the full washer face. Minimum axial load is explicit at factor A 0.67: below F_am = A·n² (or the catalogue's slow-speed floor) the cylindrical rollers skid; springs or the rotor's own weight are part of the selection, not an accessory. Mounting: locate the shaft washer on the 190 mm seat (it rotates and takes an interference fit), leave the housing washer a sliding fit in the 270 mm bore, and check the stack can tilt freely before clamping.
Typical equipment & failure modes
Common applications
- vertical electric motor and pump shafts whose rotor weight loads one bearing
- extruder and injection press screw thrust blocks at low speed
- rolling-mill screwdown mechanisms and press adjusters
- slewing and turntable pivots with predominantly axial force
Known failure patterns
- cage wear from rollers being dragged through unloaded zones under fluctuating thrust
- shaft-washer creep and fretting corrosion on a soft or undersized shaft shoulder
- oil starvation at the sliding contact zones of large spherical roller thrust bearings on forced-feed trips
- hard-particle indentation where oil or grease filtration is inadequate
- roller skidding and raceway glazing once the thrust falls below the catalogue minimum axial load (factor A)
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 62 mm.
- Keep the machined brass M cage out of chemical contact with aggressive EP additives beyond its compatibility list; cage damage here redistributes rollers and destroys the washer in hours.
- Do not substitute a thrust ball bearing of the same ISO envelope by rating alone: the cylindrical rollers of 81238 M need different minimum load and lubrication despite the shared 190×270 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 81238 M size.
- the 500 r/min reference speed is the thermal criterion under load, the 1,000 r/min limiting speed is mechanical and oil lubrication typically raises the usable figure.
- The 695/2900 kN ratings and 12000 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
Which dimensions does the 81238 M have?
A 81238 M measures 190 mm bore × 270 mm outside diameter × 62 mm width (7.48 × 10.63 × 2.441 in). From SKF catalogue PUB BU/P1 17000: dynamic C 695 kN, static C0 2900 kN, fatigue limit Pu 250 kN, reference speed 500 r/min, limiting speed 1,000 r/min, mass about 12000 g. Raceway diameters Ea 205 mm / Eb 263 mm and minimum load factor A 0.67 guide the seat design.
What is the difference between 811 and 812 series?
811 is the light section and 812 the higher, heavier section for the same bore; 893/894 are the extra-heavy series. 81238 M belongs to the heavy 812 series, 190×270×62 mm.
Are the washers of 81238 M separable?
Yes — shaft washer WS, roller-and-cage set and housing washer GS are separate and interchangeable within the size, but never across series: an 811 and an 812 washer for the same bore differ in OD and height.
Can a thrust ball bearing replace the 81238 M?
They share ISO boundary outlines (e.g. 511 vs 811), but the roller bearing needs a higher minimum axial load and different lubrication, and its C/C0 figures are not interchangeable — re-run the selection before substituting.
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.