NSK7905CTDULP4Super Precision Angular Contact Ball Bearing Matched Duplex Pair 25 x 42 x 9 mm 15 Degree Phenolic Cage Light Preload

Product Description

What this part is

A matched duplex pair of NSK 7905C super-precision angular contact ball bearings, 25 mm bore, 42 mm outside diameter, 9 mm wide each. The 71900 series is the thinnest of the super-precision angular contact sections, chosen where a spindle needs a large shaft inside a small housing bore.

Decoding the designation

In this scheme 7905 is the ISO 19-series section, equivalent to the full ISO number 71905. C sets the contact angle at 15°, T is a phenolic resin cage, DU marks the pieces as a ground duplex set, L is light preload and P4 is ABEC 7.

What these specs mean in practice

A 15° contact angle gives the highest limiting speed and the lowest axial stiffness of the standard angular contact angles, which is why grinding and high-frequency spindles use it. Light preload keeps running torque and heat generation down and leaves the most speed headroom. Phenolic resin rides the outer-ring land, is light and oil-absorbent, and works to about 120 °C, which suits oil-mist and oil-air lubrication.

Quantity and configuration

2 Pcs, supplied as one matched duplex set. Ring faces are ground together so the pair reaches the specified light preload when clamped solid, with no shims and no measurement. Stack height for the pair is 18 mm.

Thrust direction

Each bearing on its own takes thrust in one direction. Back-to-back or face-to-face, the pair takes thrust in both directions; in tandem it takes a larger load in one direction only.

Fitting notes

The V etch across the two outer-ring faces aligns to give the ground arrangement; turning one ring relative to the other changes the preload the set was ground for. The 9 mm section is shallow, so the housing shoulder and shaft nut faces carry the clamping load over a small area and their squareness governs the running accuracy achieved.

Interchange guidance

Direct substitutes are an NSK or RHP 71905C duplex pair at P4 and light preload with a phenolic cage. A 7905A5 at 25° is the same 25 x 42 x 9 mm envelope at a different angle — a related size, not an interchange. The 7005C is the wider 25 x 47 x 12 mm section and does not fit this housing bore.