NSK7008A5TRDULP4YSuper-Precision Angular Contact Ball Bearing Matched Pair – Straight Bore, 40 mm ID, 68 mm OD, 15 mm Width, Open, 25° Contact Angle, Light Preload, Phenolic Cage, P4Y, 2 Pcs

Product Description

What this part is

A matched pair of NSK 7008A5TRDULP4Y super-precision angular contact ball bearings, 40 mm bore, 68 mm outside diameter, 15 mm width per bearing. The pair is ground as a universally matchable duplex set at light preload and is supplied open on both faces. Two pieces per sale unit.

Decoding the designation

7008 is the ISO 70 light series at a 40 mm bore. A5 is NSK’s 25° contact angle. TR is an outer-ring-guided machined phenolic resin cage, rated to 120 °C. DUL is a duplex universal set at light preload. P4Y is an NSK special accuracy class held tighter than standard P4, which is itself ABEC 7. Universal matching means the two rings can be set back-to-back, face-to-face or in tandem and will still deliver the ground-in light preload with the faces simply drawn together.

What these specs mean in practice

A 25° contact angle takes appreciably more thrust than the 15° C-suffix version of the same 7008 envelope, and gives up some speed capability in exchange. Light preload is the choice where running accuracy and thermal tolerance matter more than outright stiffness, which is the normal condition in a grinding or milling spindle. Basic dynamic load rating is 20.5 kN and basic static load rating 15.1 kN per bearing; a two-bearing set arranged back-to-back or face-to-face carries roughly 1.6 times the dynamic capacity of one bearing, and takes thrust in both directions.

Speed and temperature

Limiting speed is 18,600 rpm on grease and 27,800 rpm on oil. The phenolic cage sets the upper continuous temperature at 120 °C.

Quantity and configuration

Two bearings per sale unit, forming one matched duplex set. Because the set is universally matchable, the arrangement is chosen at assembly rather than fixed by the designation.

Fitting notes

Shaft and housing seats want grinding to super-precision limits to preserve the P4Y running accuracy. The ground reference faces of the pair are marked and are brought together to establish the preload; mounting force passes through the ring being fitted, not through the balls. The bearings arrive with a preservative film rather than a service lubricant.

Interchange guidance

7008A5TRSULP4Y is the same bearing as a universally matchable single at light preload — a related size rather than a substitute for a two-piece set. SKF 7008 ACD/P4A DGA, FAG B7008-E-T-P4S-UL and Fafnir 3MM9008WI occupy the same 40 x 68 x 15 mm envelope at 25°, and each maker’s cage, preload and matching codes have to be read in that maker’s own scheme. 7008CTRDULP4Y is the 15° version of this same set.