81224-TN bearing: complete specifications & equivalents
The 81224-TN is a ISO 104 radial bearing sized 120 x 170 x 39 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 | 170 mm |
| Width B | 39 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 255 kN |
| Basic static load rating C0 | 1000 kN |
| Fatigue load limit Pu | 96.5 kN |
| Reference speed (thermal) | 800 rpm |
| Limiting speed (mechanical) | 1600 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2550 g |
| Manufacturer designation | 81224 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 | 4.724 in |
|---|---|
| Outer diameter D | 6.693 in |
| Width B | 1.535 in |
| ISO bore code | 24 |
| Radial section height (D−d)/2 | 25 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) | 16 of 28 |
| Bore above smallest 81200-series size | 90 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the 81224-TN model number is decoded
Where a thrust ball bearing of the same envelope is exhausted, 81224 TN replaces the ball complement with cylindrical rollers: 120 mm bore, 170 mm OD, rated 1000 kN static for steady hook and screw loads. Reading the code: the first three digits 812 give the dimension series (heavy 812 series), the last two 24 encode the 120 mm shaft washer bore (code 24 × 5), and TN names the cage execution. The three components are separable and interchangeable within the size: WS shaft washer, K-cage roller set, GS housing washer, all running on flat, square seats; the glass fibre reinforced PA66 TN cage is standard for this size. Selection arithmetic: C 255 kN against C0 1000 kN gives a C0/C ratio of 3.92 — thrust bearings are chosen on static rating and F_a/C0 more often than on L10 life. Mounting: locate the shaft washer on the 120 mm seat (it rotates and takes an interference fit), leave the housing washer a sliding fit in the 170 mm bore, and check the stack can tilt freely before clamping.
Typical equipment & failure modes
Common applications
- 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
- extruder and injection press screw thrust blocks at low speed
Known failure patterns
- smearing at roller-raceway contacts during unloaded startup before the oil film or preload is established
- 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
- 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 39 mm.
- 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 81224 TN size.
- the 800 r/min reference speed is the thermal criterion under load, the 1,600 r/min limiting speed is mechanical and oil lubrication typically raises the usable figure.
- The 255/1000 kN ratings assume flat, full-support washer seats; a housing face narrower than the 170 mm washer OD invalidates the rating through edge stress.
- Do not substitute a thrust ball bearing of the same ISO envelope by rating alone: the cylindrical rollers of 81224 TN need different minimum load and lubrication despite the shared 120×170 mm outline.
- The 255/1000 kN ratings and 2550 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
What ruins a 81224 TN in service?
Unloaded running below factor A 0.08 causes skidding; non-square or narrow shoulders fret the washer backs; dry starts and contamination do the rest. Speed ceiling: 1,600 r/min limiting.
Which dimensions does the 81224 TN have?
A 81224 TN measures 120 mm bore × 170 mm outside diameter × 39 mm width (4.724 × 6.693 × 1.535 in). From SKF catalogue PUB BU/P1 17000: dynamic C 255 kN, static C0 1000 kN, fatigue limit Pu 96.5 kN, reference speed 800 r/min, limiting speed 1,600 r/min, mass about 2550 g. Raceway diameters Ea 127 mm / Eb 162 mm and minimum load factor A 0.08 guide the seat design.
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. 81224 TN belongs to the heavy 812 series, 120×170×39 mm.
Are the washers of 81224 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.
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.