81208-TN bearing: complete specifications & equivalents
The 81208-TN is a ISO 104 radial bearing sized 40 x 68 x 19 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 40 mm |
| Outer diameter D | 68 mm |
| Width B | 19 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 83 kN |
| Basic static load rating C0 | 255 kN |
| Fatigue load limit Pu | 26.5 kN |
| Reference speed (thermal) | 1900 rpm |
| Limiting speed (mechanical) | 3800 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 250 g |
| Manufacturer designation | 81208 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 & 81200-series range
| Bore d | 1.575 in |
|---|---|
| Outer diameter D | 2.677 in |
| Width B | 0.748 in |
| ISO bore code | 08 |
| Radial section height (D−d)/2 | 14 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) | 3 of 28 |
| Bore above smallest 81200-series size | 10 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 81208-TN model number is decoded
SKF supplies 81208 TN as a separable thrust bearing: the 40 mm shaft washer (WS), the glass fibre reinforced PA66 TN cage holding short cylindrical rollers, and the 68 mm housing washer (GS) can be ordered and mounted individually. Reading the code: the first three digits 812 give the dimension series (heavy 812 series), the last two 08 encode the 40 mm shaft washer bore (code 08 × 5), and TN names the cage execution. Small sizes ship with glass-fibre PA66 TN cages for quiet, low-friction running; the 83 kN rating assumes oil or grease reaching the full washer face. Speed planning separates the 1,900 r/min thermal reference from the 3,800 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. Mounting: locate the shaft washer on the 40 mm seat (it rotates and takes an interference fit), leave the housing washer a sliding fit in the 68 mm bore, and check the stack can tilt freely before clamping.
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
- abrasive paste forming as dust bypasses the housing seals into the open washer set
- rolling-contact fatigue spalling after the catalogue L10 life is exhausted
- smearing at roller-raceway contacts during unloaded startup before the oil film or preload is established
Selection pitfalls — read before you substitute
- At a 40 mm seat the 19 mm stack is easy to over-clamp — a cover torqued solid removes all roller clearance; shim to the catalogue endplay and keep factor A 0.0052 as the floor.
- The 83/255 kN ratings assume flat, full-support washer seats; a housing face narrower than the 68 mm washer OD invalidates the rating through edge stress.
- Factor A 0.0052 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 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 81208 TN size.
- the 1,900 r/min reference speed is the thermal criterion under load, the 3,800 r/min limiting speed is mechanical and oil lubrication typically raises the usable figure.
- The 83/255 kN ratings and 250 g mass are SKF catalogue values transcribed from ch. 11.1 of PUB BU/P1 17000 (PDF table page 890); 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 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. 81208 TN belongs to the heavy 812 series, 40×68×19 mm.
Are the washers of 81208 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 81208 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 81208 TN in service?
Unloaded running below factor A 0.0052 causes skidding; non-square or narrow shoulders fret the washer backs; dry starts and contamination do the rest. Speed ceiling: 3,800 r/min limiting.
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.