Koyo NTA-815 thrust needle roller and cage assembly, 12.7 x 23.8 x 1.984 mm

These Koyo NTA thrust needle roller and cage assemblies are inch series assemblies that use needle rollers of the smallest practical diameter. 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.

The cage is a hardened assembly of two securely fastened mating pieces, with through-hardened, precision-ground and lapped needle rollers. This construction minimises cage stress and keeps the roller retaining function of the cage unaffected by normal wear.

The range has 16 sizes with bore diameters from 12.7 to 95.25 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

• Hardened two-piece cage with through-hardened, precision-ground and lapped needle rollers
• Transmits thrust load between relatively rotating parts with greatly reduced friction
• Very thin section for compact designs: thickness 1.984 to 3.175 mm
• Basic dynamic load rating C 7.16 to 56.05 kN and basic static load rating C0a 19.13 to 344.3 kN
• Oil lubrication speed rating 3,500 to 19,000 min-1
• Bore piloting preferred; matching TRA to TRD thrust washers available

Key specifications

Available sizes

Selecting the right option

Choose the size from the shaft (the bore diameter Dc1) and the housing (the outside diameter Dc). The designation encodes the inch size: for example NTA-1625 has a bore of 16/16 in (1 in) and an outside diameter of 25/16 in (1 9/16 in).

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.

The speed ratings are based on adequate oil lubrication. Because the designation does not appear on the bearing itself, confirm it from your parts list when ordering for replacement.

Fitting and use

Pilot the assembly on its bore where possible: the cage bore has a larger contact area and a closer tolerance than the outer diameter. Harden the piloting surface for the cage to at least 55 HRC. Where the design prevents bore piloting, the assembly can be piloted on its outer diameter, but the diameter to clear washer OD given in the washer tables is not suitable for that, so determine suitable OD piloting dimensions with your AIMS representative.

Bore tolerance is +0.051 to +0.178 mm and outer diameter tolerance -0.508 to -0.254 mm for assemblies with the 1.984 mm roller diameter, and +0.051 to +0.254 mm and -0.635 to -0.254 mm for the 3.175 mm roller diameter.

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.

Related products

Also available from Koyo: the Koyo TRA to TRD thrust washer range.