SKF7217-ACDGA/P4ASuper-Precision Angular Contact Ball Bearing – 85 mm ID, 150 mm OD, 28 mm Width, Open, 25° Contact Angle, Light Preload, Machined Phenolic Cage, P4A

Product Description

What this part is

An SKF 7217 ACDGA/P4A super-precision single-row angular contact ball bearing, 85 mm bore, 150 mm outside diameter, 28 mm width. It carries radial and axial load simultaneously, with the axial component taken in one direction only. The bearing is open on both faces and supplied with a light preload as a universally matchable single unit.

Decoding the designation

The 72 series sets the cross-section for an 85 mm bore. ACD is SKF’s 25° contact angle super-precision design. GA is a preload class, not a mounting direction — SKF’s ladder runs GA light, GB medium, GC heavy. P4A is SKF’s super-precision dimensional and running accuracy class, broadly ABEC 7. Because the bearing is universally matchable, any two or more units can be set back-to-back, face-to-face or in tandem and will deliver the published preload without shims or grinding.

What these specs mean in practice

A 25° contact angle carries substantially more thrust than a 15° design of the same envelope, at the cost of some speed capability. Light preload favours running accuracy and speed over rigidity, which is the usual choice for a grinding or milling spindle where thermal growth has to be tolerated. The machined phenolic cage is outer-ring guided and runs quietly at speed with low mass; it is a fabric-base laminate, not a polyamide. Basic dynamic load rating is 95.6 kN and basic static load rating 85 kN, on 17 chrome steel balls of 19.05 mm diameter.

Speed and temperature

Limiting speed is 13 000 rpm under oil lubrication and 8 000 rpm under grease. Continuous operating temperature range is −30 to 110 °C, the upper figure set by the phenolic cage rather than the steel.

Quantity and configuration

One bearing per sale unit. This is a universally matchable single, so a set of any size can be built from identical units.

Fitting notes

Bore tolerance is −0.008 to 0 mm and outside diameter tolerance −0.009 to 0 mm, so shaft and housing seats want to be ground to matching super-precision limits. Mounting force is applied to the ring being fitted, never transmitted through the balls.

Interchange guidance

7217 ACD/P4A DGA is the same bearing written with the suffix order reversed. 7217 ACDGB/P4A is the medium-preload version of the same envelope and angle — a related size, not a substitute. Fafnir 3MM217WI and NSK 7217A5 occupy the same 85 x 150 x 28 mm envelope at 25°, but each maker’s cage, preload and matching suffixes carry their own meaning and have to be read in that maker’s scheme.