AXK0821-TN bearing: complete specifications & equivalents
The AXK0821-TN is a ISO 3031 radial bearing sized 8 x 21 x 2 mm (bore x OD x width). Verify dimensions against the official catalog before ordering.
Specification table
| Parameter | Value |
|---|---|
| Brand | SKF |
| Bore diameter d | 8 mm |
| Outer diameter D | 21 mm |
| Width B | 2 mm |
| Material | GCr15 |
| Seal / shield | open |
| Internal clearance | CN |
| Tolerance class | P0 |
| Cage | polymer (PA66 glass-fibre reinforced) |
| Basic dynamic load rating C | 7.2 kN |
| Basic static load rating C0 | 20 kN |
| Fatigue load limit Pu | 2.32 kN |
| Reference speed (thermal) | 5600 rpm |
| Limiting speed (mechanical) | 11000 rpm |
| Operating temperature | -40 to +120 °C |
| Mass | 2 g |
| Manufacturer designation | AXK 0821 TN |
| Standard | ISO 3031 |
| Catalog version | SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 12.1 needle roller and cage thrust assemblies |
| Last verified | 2026-09-27 |
Source: catalog reference (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 12.1 needle roller and cage thrust assemblies) · extracted 2026-09-27
Parameters extracted from the official SKF Rolling Bearings catalogue (SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 12.1 needle roller and cage thrust assemblies); 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 & AXK-series range
| Bore d | 0.315 in |
|---|---|
| Outer diameter D | 0.827 in |
| Width B | 0.079 in |
| ISO bore code | 21 |
| Radial section height (D−d)/2 | 6.5 mm |
| Smallest bore in AXK-series | 4 mm |
| Largest outer diameter in AXK-series | 200 mm |
| Width range across AXK-series | 2–5 mm |
| Bore position in AXK-series (smallest first) | 4 of 30 |
| Bore above smallest AXK-series size | 4 mm |
Cross references & equivalents
No verified interchange data yet. Send an inquiry and our team will confirm equivalents manually.
How the AXK0821-TN model number is decoded
In SKF catalogue PUB BU/P1 17000, AXK 0821 TN denotes the needle thrust assembly whose code reads the raceway diameters directly — 08/21 — intended to run against hardened, ground washers or machine faces. In AXK 0821 TN the number is the boundary plan, not a bore code: 08/21, with the 2 mm assembly thickness fixed by the ISO 3031 plan and Ea/Eb 9/20 mm marking the actual needle-contact band. Washer selection is part of the bearing: too-soft faces rib within weeks even though the 7.2 kN rating is unchanged — the AXK code only supplies the rolling elements. Speed planning separates the 5,600 r/min thermal reference from the 11,000 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. Grease both faces before assembly so the needles stay in their pockets, especially for the tiny 2 mm thin set; after fitting, rotate slowly and confirm the cage does not catch on the shoulder edges.
Typical equipment & failure modes
Common applications
- torque converter and clutch release assemblies in passenger cars
- small gearbox gears that need a 2 mm thrust shim between a shaft and face
- light turntables, index plates and office-machine pivots
- two-wheeler gearbox selector and layshaft thrust faces
Known failure patterns
- edge loading across the needle crowns when the mating faces are not square to the shaft
- cage wear from rollers being dragged through unloaded zones under fluctuating thrust
- abrasive paste forming as dust bypasses the housing seals into the open washer set
- condensation pitting in machines that run intermittently in humid environments
- needle-row denting from a single hard particle trapped in the 2 mm section
Selection pitfalls — read before you substitute
- The AXK 0821 TN is watchmaking-scale (2 mm thick, 2 g): handle it with tweezers, grease it onto its washer, and assume one dropped or cocked assembly is one ruined bearing.
- the 5,600 r/min reference speed is the thermal criterion under load, the 11,000 r/min limiting speed assumes hardened, ground, oiled faces; soft or dry faces drop the real ceiling drastically.
- The 7.2 kN rating is real only at 58–64 HRC face hardness; visual inspection cannot tell a 45 HRC washer from a 60 HRC one — order certified washers.
- The AXK code supplies no washers: AXK 0821 TN arrives as the needle cage only, and a "bearing failure" on hard-faced tracks is usually a missing-AS-washer failure at ordering time.
- Match washers by the exact 8–21 mm track — a washer sized to the shaft alone leaves the needles overrunning its edge, which shears the cage.
- The 7.2/20 kN ratings and 2 g mass are SKF catalogue values transcribed from ch. 12.1 of PUB BU/P1 17000 (PDF table page 908); 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 AXK 0821 TN code read?
AXK marks the needle thrust assembly and 08/21 gives the inner 8 mm and outer 21 mm track diameters directly; the assembly is 2 mm thick. TN means the polymer cage instead of stamped steel.
What minimum hardness do the mating faces need?
58–64 HRC with a ground raceway finish. A softer face looks fine after assembly but the needles rib and score it within weeks despite the 7.2 kN catalogue rating — order certified washers if the shaft/housing cannot be heat treated.
How is an AXK thrust assembly mounted?
Harden or washer-face both tracks across Ea 9–Eb 20 mm, keep faces parallel, locate the cage concentrically against a shoulder or register, grease the needles so they stay pocketed, and never press through them.
What are the dimensions and ratings of the AXK 0821 TN?
A AXK 0821 TN measures 8 mm bore × 21 mm outside diameter × 2 mm width (0.315 × 0.827 × 0.079 in). From SKF catalogue PUB BU/P1 17000: dynamic C 7.2 kN, static C0 20 kN, fatigue limit Pu 2.32 kN, reference speed 5,600 r/min, limiting speed 11,000 r/min, mass about 2 g. The contact band runs Ea 9–Eb 20 mm; hardened washers or 58–64 HRC faces are required.
Reviewed & verified by the MPN Base engineering desk against source catalog SKF PUB BU/P1 17000/1 EN (Oct 2018), ch. 12.1 needle roller and cage thrust assemblies on 2026-09-27. Read our editorial & correction policy.