Koyo TRA-1625 thrust washer, 25.4 x 39.67 x 0.81 mm

These Koyo TRA, TRB, TRC and TRD thrust washers are inch series thrust washers for NTA thrust needle roller and cage assemblies. The letters after TR show the washer thickness, and TRA is the thinnest washer made to inch nominal dimensions. Most are intended to be piloted on their bores.

The thinner washers are tumble burnished and may be out of flat because of heat treatment, but they flatten under load. The raceway surfaces of thick thrust washers are ground and lapped. Thrust washers should be stationary with respect to, and piloted by, their supporting or backing member, with no rubbing action between the washer and any other machine member.

The range has 56 sizes in four thicknesses, 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

• Four thicknesses: TRA 0.81 mm, TRB 1.6 mm, TRC 2.41 mm and TRD 3.2 mm
• Mostly bore-piloted washers for NTA thrust needle roller and cage assemblies
• Bore area burnished for piloting; outside diameter as blanked
• Bore diameters 12.7 to 95.25 mm and outside diameters 23.8 to 117.48 mm
• Piloting and clearance dimensions listed for each size

Key specifications

Available sizes

Selecting the right option

Choose the washer from the bore and outside diameter of the NTA assembly it backs, and the thickness letter. The designation encodes the inch size: for example TRA-1625 has a bore of 16/16 in (1 in) and an outside diameter of 25/16 in (1 9/16 in).

TRC-1625 is not printed in the Koyo catalogue. Its dimensions follow the 1625 size of the TRA, TRB and TRD washers and the TRC thickness.

Fitting and use

The bore diameter tolerance is +0.050 to +0.300 mm for bores up to 57.2 mm and +0.050 to +0.430 mm for bores over 57.2 mm up to 133.4 mm. The outside diameter tolerance is -0.762 to -0.254 mm.

If the shaft and the housing next to the bearing outside diameter are not concentric, add the total indicator reading between them to the diameter to clear the washer OD (H) given in the variant specification.

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.

Related products

Also available from Koyo: the Koyo NTA thrust assembly range.