81124-TN bearing: complete specifications & equivalents
The 81124-TN is a ISO 104 radial bearing sized 120 x 155 x 25 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 120 mm |
| Outer diameter D | 155 mm |
| Width B | 25 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 170 kN |
| Basic static load rating C0 | 735 kN |
| Fatigue load limit Pu | 68 kN |
| Reference speed (thermal) | 1100 rpm |
| Limiting speed (mechanical) | 2200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1100 g |
| Manufacturer designation | 81124 TN |
| 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 | 4.724 in |
|---|---|
| Outer diameter D | 6.102 in |
| Width B | 0.984 in |
| ISO bore code | 24 |
| Radial section height (D−d)/2 | 17.5 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) | 20 of 34 |
| Bore above smallest 81100-series size | 105 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 81124-TN model number is decoded
The light 811 series bearing 81124 TN carries pure axial load at low to moderate speed: 170 kN dynamic and 735 kN static across a 120×155 mm washer pair, 25 mm overall height. In 81124 TN, 811 fixes the 155 mm OD and 25 mm height; 24 selects the 120 mm seat, and the glass fibre reinforced PA66 TN 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 25 mm height. Speed planning separates the 1,100 r/min thermal reference from the 2,200 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 0.043) 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
- smearing at roller-raceway contacts during unloaded startup before the oil film or preload is established
- shaft-washer creep and fretting corrosion on a soft or undersized shaft shoulder
- abrasive paste forming as dust bypasses the housing seals into the open washer set
- brinelling of washer raceways from impact or mounting force applied through the rolling elements
- cage wear from rollers being dragged through unloaded zones under fluctuating thrust
Selection pitfalls — read before you substitute
- At 120 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 25 mm.
- Factor A 0.043 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 glass fibre reinforced PA66 TN 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 81124 TN need different minimum load and lubrication despite the shared 120×155 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 81124 TN size.
- The 170/735 kN ratings and 1100 g mass are SKF catalogue values transcribed from ch. 11.1 of PUB BU/P1 17000 (PDF table page 892); 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 is the 81124 TN designation read?
The first three digits 811 give the dimension series (light 811 series); 24 encodes the 120 mm bore (code 24 × 5); the suffix denotes the glass fibre reinforced PA66 TN cage. WS and GS washers of the same size can be ordered separately.
Why does 81124 TN need a minimum axial load?
Below factor A 0.043 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 81124 TN 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.
How should a 81124 TN 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 0.043 minimum load is present.
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.