81248-M bearing: complete specifications & equivalents
The 81248-M is a ISO 104 radial bearing sized 240 x 340 x 78 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 240 mm |
| Outer diameter D | 340 mm |
| Width B | 78 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | brass |
| Basic dynamic load rating C | 1100 kN |
| Basic static load rating C0 | 4900 kN |
| Fatigue load limit Pu | 390 kN |
| Reference speed (thermal) | 400 rpm |
| Limiting speed (mechanical) | 800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 22000 g |
| Manufacturer designation | 81248 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 | 9.449 in |
|---|---|
| Outer diameter D | 13.386 in |
| Width B | 3.071 in |
| ISO bore code | 48 |
| Radial section height (D−d)/2 | 50 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) | 26 of 28 |
| Bore above smallest 81200-series size | 210 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 81248-M model number is decoded
81248 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 240×340×78 mm, listed in SKF catalogue PUB BU/P1 17000 ch. 11.1. In 81248 M, 812 fixes the 340 mm OD and 78 mm height; 48 selects the 240 mm seat, and the machined brass M cage is the only execution suffix on these rigid-washer bearings. Rigid washers mean no self-alignment: the shaft and housing shoulders must be square and parallel to within the catalogue seat tolerances, or the rollers edge-load across the 78 mm height. Speed planning separates the 400 r/min thermal reference from the 800 r/min mechanical limiting speed. Thrust bearings govern the thermal speed of many vertical arrangements, and oil circulation raises the usable speed substantially above grease values. Press only on washer backs, never through the roller set; seat both washers against full-area square shoulders, and shim the housing cover so the minimum load (A 1.92) is present without clamping the rollers.
Typical equipment & failure modes
Common applications
- screw jack and lifting screw thrust positions under slow, steady load
- 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
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
- grease churning and overheating when a high-speed thrust position is over-packed
- brinelling of washer raceways from impact or mounting force applied through the rolling elements
- smearing at roller-raceway contacts during unloaded startup before the oil film or preload is established
Selection pitfalls — read before you substitute
- At 240 mm bore the 22 kg washer set needs forced lubrication and controlled start-up sequencing; dry first rotation under load is the classic destruction mode for very large thrust bearings.
- Do not substitute a thrust ball bearing of the same ISO envelope by rating alone: the cylindrical rollers of 81248 M need different minimum load and lubrication despite the shared 240×340 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 81248 M size.
- Factor A 1.92 is a mounting requirement, not advice: below the minimum axial load the rollers skid at speed — most "mysterious" early thrust failures are unloaded running.
- 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.
- The 1100/4900 kN ratings and 22000 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
What are the dimensions and ratings of the 81248 M?
A 81248 M measures 240 mm bore × 340 mm outside diameter × 78 mm width (9.449 × 13.386 × 3.071 in). From SKF catalogue PUB BU/P1 17000: dynamic C 1100 kN, static C0 4900 kN, fatigue limit Pu 390 kN, reference speed 400 r/min, limiting speed 800 r/min, mass about 22000 g. Raceway diameters Ea 263 mm / Eb 333 mm and minimum load factor A 1.92 guide the seat design.
How is the 81248 M designation read?
The first three digits 812 give the dimension series (heavy 812 series); 48 encodes the 240 mm bore (code 48 × 5); the suffix denotes the machined brass M cage. WS and GS washers of the same size can be ordered separately.
Why does 81248 M need a minimum axial load?
Below factor A 1.92 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.
Can the 81248 M take reversing thrust?
No. It carries axial load in one direction only; reversing force unloads and impacts the roller set. Use a mirrored pair of bearings for reversing shafts, with a separate arrangement for radial load.
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.