81120-TN bearing: complete specifications & equivalents
The 81120-TN is a ISO 104 radial bearing sized 100 x 135 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 | 100 mm |
| Outer diameter D | 135 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 | 156 kN |
| Basic static load rating C0 | 630 kN |
| Fatigue load limit Pu | 62 kN |
| Reference speed (thermal) | 1200 rpm |
| Limiting speed (mechanical) | 2400 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 950 g |
| Manufacturer designation | 81120 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 | 3.937 in |
|---|---|
| Outer diameter D | 5.315 in |
| Width B | 0.984 in |
| ISO bore code | 20 |
| 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) | 18 of 34 |
| Bore above smallest 81100-series size | 85 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 81120-TN model number is decoded
Where a thrust ball bearing of the same envelope is exhausted, 81120 TN replaces the ball complement with cylindrical rollers: 100 mm bore, 135 mm OD, rated 630 kN static for steady hook and screw loads. SKF thrust-roller numbering mirrors the ball 511/512 plan with 811/812: 812 is the higher (heavier) section per bore, and 893/894 are the very heavy series — 81120 TN sits in the light 811 series. 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. One direction only: 81120 TN cannot be reversed to take opposite thrust — mirror a second bearing for reversing shafts, and keep housing and shaft seats square within the ISO 104 tolerances. 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 0.032) is present without clamping the rollers.
Typical equipment & failure modes
Common applications
- 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
- vertical electric motor and pump shafts whose rotor weight loads one bearing
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
- abrasive paste forming as dust bypasses the housing seals into the open washer set
- electrical erosion of raceways on VFD-driven shafts without grounding or insulation
- roller skidding and raceway glazing once the thrust falls below the catalogue minimum axial load (factor A)
Selection pitfalls — read before you substitute
- At 100 mm bore the minimum load (A 0.032) is still small, but a vertical shaft at rest loses it entirely — specify springs or check the rotor weight exceeds F_am at zero speed.
- 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 81120 TN need different minimum load and lubrication despite the shared 100×135 mm outline.
- The 156/630 kN ratings assume flat, full-support washer seats; a housing face narrower than the 135 mm washer OD invalidates the rating through edge stress.
- Factor A 0.032 is a mounting requirement, not advice: below the minimum axial load the rollers skid at speed — most "mysterious" early thrust failures are unloaded running.
- The 156/630 kN ratings and 950 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
Are the washers of 81120 TN 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 81120 TN?
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.
What ruins a 81120 TN in service?
Unloaded running below factor A 0.032 causes skidding; non-square or narrow shoulders fret the washer backs; dry starts and contamination do the rest. Speed ceiling: 2,400 r/min limiting.
Which dimensions does the 81120 TN have?
A 81120 TN measures 100 mm bore × 135 mm outside diameter × 25 mm width (3.937 × 5.315 × 0.984 in). From SKF catalogue PUB BU/P1 17000: dynamic C 156 kN, static C0 630 kN, fatigue limit Pu 62 kN, reference speed 1,200 r/min, limiting speed 2,400 r/min, mass about 950 g. Raceway diameters Ea 104 mm / Eb 131 mm and minimum load factor A 0.032 guide the seat design.
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.