81217-TN bearing: complete specifications & equivalents
The 81217-TN is a ISO 104 radial bearing sized 85 x 125 x 31 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 85 mm |
| Outer diameter D | 125 mm |
| Width B | 31 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 | 640 kN |
| Fatigue load limit Pu | 67 kN |
| Reference speed (thermal) | 1100 rpm |
| Limiting speed (mechanical) | 2200 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 1200 g |
| Manufacturer designation | 81217 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 | 3.346 in |
|---|---|
| Outer diameter D | 4.921 in |
| Width B | 1.22 in |
| ISO bore code | 17 |
| Radial section height (D−d)/2 | 20 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) | 12 of 28 |
| Bore above smallest 81200-series size | 55 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 81217-TN model number is decoded
Where a thrust ball bearing of the same envelope is exhausted, 81217 TN replaces the ball complement with cylindrical rollers: 85 mm bore, 125 mm OD, rated 640 kN static for steady hook and screw loads. The designation 81217 TN states 812 series, 85 mm bore, glass fibre reinforced PA66 TN cage; shaft and housing washers are also orderable separately as WS and GS parts of the same size. The bearing takes thrust in one direction only — reverse loads lift the roller set off its track; arrange a mirrored second bearing for reversing duty, and keep the applied load above factor A 0.033. One direction only: 81217 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. Mounting: locate the shaft washer on the 85 mm seat (it rotates and takes an interference fit), leave the housing washer a sliding fit in the 125 mm bore, and check the stack can tilt freely before clamping.
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
- roller skidding and raceway glazing once the thrust falls below the catalogue minimum axial load (factor A)
- washer back-face fretting where the seat is too narrow to support the full ring face
- grease churning and overheating when a high-speed thrust position is over-packed
- hard-particle indentation where oil or grease filtration is inadequate
- smearing at roller-raceway contacts during unloaded startup before the oil film or preload is established
Selection pitfalls — read before you substitute
- At 85 mm bore the minimum load (A 0.033) 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.
- Do not substitute a thrust ball bearing of the same ISO envelope by rating alone: the cylindrical rollers of 81217 TN need different minimum load and lubrication despite the shared 85×125 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 81217 TN size.
- the 1,100 r/min reference speed is the thermal criterion under load, the 2,200 r/min limiting speed is mechanical and oil lubrication typically raises the usable figure.
- The 170/640 kN ratings assume flat, full-support washer seats; a housing face narrower than the 125 mm washer OD invalidates the rating through edge stress.
- The 170/640 kN ratings and 1200 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
Why does 81217 TN need a minimum axial load?
Below factor A 0.033 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 81217 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 81217 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 0.033 minimum load is present.
What are the dimensions and ratings of the 81217 TN?
A 81217 TN measures 85 mm bore × 125 mm outside diameter × 31 mm width (3.346 × 4.921 × 1.22 in). From SKF catalogue PUB BU/P1 17000: dynamic C 170 kN, static C0 640 kN, fatigue limit Pu 67 kN, reference speed 1,100 r/min, limiting speed 2,200 r/min, mass about 1200 g. Raceway diameters Ea 90 mm / Eb 119 mm and minimum load factor A 0.033 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.