NSK7912A5TRDULP3Super Precision Angular Contact Ball Bearing Matched Pair – 60 mm ID, 85 mm OD, 13 mm Width, Open, 25° Contact Angle, Light Preload, P3 Class, 2 Pcs.

Product Description

What this part is

NSK 7912A5TRDULP3 super precision angular contact ball bearings, supplied as a matched duplex pair. 60 mm bore, 85 mm outside diameter, 13 mm width per bearing. Open on both faces, phenolic cage guided on the outer ring, 25° contact angle, light preload, P3 special class. The carton also carries 71912 and 3MM9312WI CR DUL.

Decoding the designation

7 marks NSK’s high-accuracy angular contact standard series and 9 the 19 dimension series, the thin-section series. The bore number 12 multiplied by five gives the 60 mm bore. A5 is NSK’s code for 25°, confirmed by the 3MM prefix on the Fafnir-scheme marking. TR is the phenolic resin cage guided on the outer ring. DU is the universal pairing of two rows and L light preload. P3 is a special class combining ISO Class 4 dimensional tolerances with ISO Class 2 running accuracy.

What these specs mean in practice

P3 is the headline spec. Bore and outside diameter are held to Class 4 while radial and axial runout are tightened to Class 2, a grade above the usual P4 spindle bearing, which is the specification chosen where surface finish depends on runout. The 19 dimension series keeps the section slim, useful where axial space at the spindle nose is short. A 25° contact angle gives more thrust capacity and axial stiffness than a 15° bearing in the same envelope. The outer-ring-guided phenolic cage is light and self-lubricating and stays stable at speed.

Quantity and configuration

2 Pcs, one matched duplex pair, ground so the light preload comes up on assembly with no shimming. Load ratings and limiting speed listed are per bearing.

Fitting notes

Assembly is dry and clean, interference fit on the inner rings, location fit in the housing bore, both rings clamped fully home against their shoulders so the ground offset closes. The arrangement mark on the outer ring faces sets the orientation. Because the running accuracy is Class 2, the shaft seat and housing bore need to be ground and measured to a matching standard for the class to be realised. Heat is applied to the shaft rather than the bearing.

Interchange guidance

A 60 x 85 x 13 mm 25° duplex pair at light preload in the same P3 class substitutes directly. The same number in P4 or P4S shares the envelope but has looser runout, so it is a related size where the Class 2 accuracy was specified. A 15° part in this envelope, or the same part at medium or heavy preload, is also a related size.