SKF71905ACDP4ADGASuper-Precision Angular Contact Ball Bearing, Matched Pair – 25 mm ID, 42 mm OD, 9 mm Width, Open, 25°, Extra Light Preload

Product Description

What this part is

An SKF 71905 ACD/P4A DGA super-precision angular contact ball bearing set. Bore 25 mm, outside diameter 42 mm, width 9 mm per bearing, 18 mm across the pair. Open on both faces, single row of balls in each bearing, running on a ball-centred fabric-base laminate phenolic cage. Supplied as a factory-matched pair of two bearings.

Decoding the designation

In the SKF super-precision scheme, 71905 is the ISO 719 extra-light dimension series with a 25 mm bore. ACD sets a 25° contact angle; the plain CD form of the same envelope is 15°. P4A is SKF’s super-precision dimensional and running accuracy class, equivalent to ABEC 7. DGA marks a universally matchable set of two bearings, extra light preload.

What these specs mean in practice

A 25° contact angle carries more axial load and less speed than a 15° bearing of the same envelope, so the ACD variant suits spindles where thrust and axial stiffness dominate. The phenolic cage is light and self-lubricating, which is what allows the 40 000 r/min reference speed. Basic dynamic load rating is 7.4 kN and basic static load rating 4.8 kN per bearing.

Preload and clearance

Universally matchable sets are ground with offset faces so that clamping the rings together produces a defined extra light preload. Preload replaces running clearance, so a radial internal clearance class does not apply to this bearing.

Quantity and configuration

Two bearings, one matched set. Because the set is universally matchable, the pair mounts back-to-back, face-to-face or in tandem, and further bearings from the same DGA designation stack into the same arrangement.

Fitting notes

Shaft and housing seats are ground to match the P4A ring tolerances; a standard-tolerance seat gives away the accuracy the class is bought for. Rings are clamped axially against ground abutment faces. Oil is the reference lubricant for the published speed rating.

Interchange guidance

FAG B71905-E-T-P4S-DUL and NSK 7905A5TYNDULP4 are the nearest 25° universally matchable pairs from the other super-precision makers; both are ground to light preload, one grade above this extra light DGA preload. SKF 71905 CD/P4ADGA shares the envelope but runs a 15° contact angle, making it a related size rather than a substitution.