SKFSuper-Precision Angular Contact Ball Bearing 50x90x20 mm, 15° Contact Angle, P4A / ABEC 7, Light Preload, Universally Matchable, Phenolic Cage – Single Bearing

Product Description

What this part is

SKF 7210 CD/P4DGA super-precision single-row angular contact ball bearing. Bore: 50 mm. Outside diameter: 90 mm. Width: 20 mm. Contact Angle: 15°. Precision Class: P4A (ABEC 7). Preload: light (A). Series: 72 light dimension series, 7210. Cage: machined fabric-reinforced phenolic, outer-land-riding. Closure: open. Country of manufacture: Italy.

Decoding the designation

72: light dimension series for angular contact ball bearings. 10: size code, 50 mm bore. C: 15° contact angle in SKF’s super-precision range. D: SKF high-capacity super-precision internal design. P4: super-precision tolerance class, ABEC 7, written P4A in the current catalogue. DG: duplex, universally matchable, universally ground — faces are ground so any two bearings from the range set against each other. A: light preload. DGA together designates a universally matchable arrangement at light preload. Current-catalogue equivalents: 7210 CD/P4ADGA, and 7210 CDGA/P4A for a single bearing of the same specification.

Universal matchability

A universally matchable bearing is ground to a tight standardised offset, so any two units from the range deliver the specified light preload in any of the three arrangements: DB back-to-back, DF face-to-face, DT tandem. Shims, grinding and a factory pairing certificate are all outside the process. Stacks of three or four can be built up, and one bearing can be replaced individually within an existing set. Back-to-back gives the widest effective load spread and the most moment stiffness. Face-to-face accommodates more shaft-to-housing misalignment. Tandem doubles axial capacity in one direction.

What these specs mean in practice

The 15° contact angle sits at the high-speed, high-radial-stiffness end of the angular contact range. A shallower angle places the ball load path closer to radial, which reduces centrifugal ball loading and gyroscopic heat generation at speed and raises radial rigidity, giving very high permissible speeds. A 25° or 40° bearing of the same envelope carries substantially more thrust and less speed. Light preload removes internal play and raises stiffness and running accuracy at the friction and heat level suited to high speed; medium and heavy preload serve lower-speed, higher-rigidity work. Preload is a property of the pair. P4A / ABEC 7 governs bore, outside diameter, width and running accuracy tolerances, and is what allows an assembled spindle to hold single-digit-micron runout.

Published ratings and mounting data

Bore d: 50 mm. Outside diameter D: 90 mm. Width B: 20 mm per bearing, 40 mm for two set together. Contact angle: 15°. Basic dynamic load rating C: 44.9 kN. Basic static load rating C₀: 34 kN. Fatigue load limit Pᵘ: 1.43 kN. Limiting speed, grease lubrication: 16 000 r/min. Limiting speed, oil lubrication: 26 000 r/min. Tolerance class: P4A (ABEC 7). Preload class: light (A). Cage: fabric-reinforced phenolic, machined. Closure: open. Mass: approximately 0.46 kg per bearing. Harmonization Code: 8482.10.50.

Set composition

Unit Quantity: 1 Pc, single bearings sold individually. Any two units form a correct light-preload DB, DF or DT pair, so a pair is two units and a single unit completes an existing set. The DGA marking is carried in the title and cross-references as a search term. The bearings are individually sealed in separate polythene bags, one bearing per bag.

Mounting data

Super-precision bearings hold their accuracy through clean handling and square mounting. Bearings stay bagged until the moment of fitting, and the preservative is left intact. Mounting is by even axial force on the ring being fitted, applied clear of the balls. Shaft and housing seats are ground to a matching precision, since an ABEC 7 bearing on a low-precision seat delivers low-precision accuracy. Both bearings of a pair share the same preload class and the same matchable range, and the arrangement marks are respected. Grease is filled sparingly on a 15° high-speed bearing. Thermal growth in the shaft is allowed for when setting the axial location of the second bearing position.

Interchange guidance

The ISO base number is 7210. For a super-precision bearing an interchange corresponds on tolerance class, contact angle, preload class and matchability as well as on the base number. Same-envelope 50 × 90 × 20 mm super-precision equivalents at 15° and light preload: NSK 7210CTYNSULP4 (NSK uses C for 15°, SU for single universal, L for light preload), FAG / Schaeffler B7210-C-T-P4S-UL, NTN 7210CG/GNP4, and Timken / Fafnir 2MM9110WI SUL, where Fafnir’s 2MM denotes 15°. The 25° counterparts of the same envelope are SKF 7210 ACD, FAG B7210-E, NSK 7210A5 and Fafnir 3MM9110WI, which differ in axial stiffness and speed capability. Standard-tolerance 7210 bearings serve general-purpose positions. MRC precision lines are consolidated under SKF, and SNFA super-precision under Schaeffler.