Koyo AXK0821TN thrust needle roller and cage assembly, 8 x 21 x 2 mm

These Koyo AXK TN thrust needle roller and cage assemblies are in the AXK series, which has a one-piece cage similar in design to the profiled steel cages used in Koyo radial needle roller bearings. Thrust needle roller and cage assemblies are complements of small-diameter needle rollers arranged in a spoke-like configuration and equally spaced by a cage, whose web separates the rollers and guides them in an orbital path. They transmit a thrust load between two relatively rotating parts while greatly reducing friction, and their very small cross section suits compact designs.

An AXK assembly is very thin. When it runs directly against the backup surface raceways, its section equals the diameter of the needle rollers, which is between 2.000 and 5.000 mm across the AXK range. Where the backup surfaces cannot be hardened and ground, Koyo supplies hardened washers in different thicknesses, such as the Koyo AS thin thrust washer.

The range has 2 sizes with bore diameters from 6 to 8 mm. Koyo bearings are made by JTEKT Corporation.

Where this product is used

• Automotive automatic and manual transmissions
• Automotive accessories such as compressors and steering gears
• Agricultural and construction equipment

Features

• Needle rollers in a one-piece cage, with a thickness equal to the roller diameter (2 mm)
• Transmits thrust load between relatively rotating parts with greatly reduced friction
• Very small cross section for compact designs
• Basic dynamic load rating C 6.37 to 8.34 kN and basic static load rating C0a 14.3 to 21.1 kN
• Oil lubrication speed rating 20,000 to 23,000 min-1
• Bore piloting preferred, because the cage bore has a closer tolerance than the outer diameter

Key specifications

Available sizes

Selecting the right option

Choose the size from the shaft (the bore diameter Dc1), the housing (the outside diameter Dc) and the available thickness Dw. Each size has an AS thin thrust washer with the same bore and outside diameter for use where the mating surface cannot be hardened and ground as a raceway.

Slippage can occur if the axial load is too light and the speed is high, particularly with inadequate lubrication. For satisfactory operation the applied axial load should be at least C0a/2200 kN, where C0a is the basic static load rating in kN.

Fitting and use

Pilot the assembly on its bore where possible: the cage bore has a closer tolerance than the outer diameter. The suggested shaft tolerance for shaft piloting is h8, and the suggested housing tolerance for housing piloting is H8. To reduce wear, harden the piloting surface for the cage to at least 55 HRC.

Thrust raceway surfaces must be ground to a surface finish of 0.2 µm Ra. Where the backup surfaces are used directly as raceways they must be parallel and hardened to at least 58 HRC, and lower hardness reduces the load ratings. Where that cannot be achieved, use thrust washers. The raceway or the surface backing a washer must be square with the shaft axis and must not be dished or coned.

Oil is the preferred lubricant for thrust needle roller and cage assemblies, and an ample oil flow is necessary for high speeds, or for moderate speeds when the load is relatively high.

The outside diameter tolerance of AXK assemblies is c13 and the bore tolerance is E12.

Related products

Also available from Koyo: the Koyo AXK thrust assembly range and the Koyo AS thin thrust washer range.