SKF7209CDP4ADGBSuper-Precision Angular Contact Ball Bearing, 45 x 85 x 19 mm, 15 Degree Contact Angle, P4A, Universally Ground

Product Description

What this part is

An SKF 7209 CD/P4A DGB super-precision angular contact ball bearing, 45 mm bore, 85 mm outside diameter, 19 mm width, open on both faces. The ball contact line runs at an angle across the raceways rather than radially, so the bearing carries thrust in one direction together with radial load, and a second bearing mounted opposed is what locates a shaft in both directions.

Decoding the designation

The 72 dimension series is the medium angular contact series and the bore code 09 gives 45 mm. CD is SKF’s 15° contact angle in the super-precision programme, distinct from ACD at 25°. P4A is SKF’s super-precision tolerance class, tightening dimensional accuracy and running accuracy well beyond a normal-class bearing. DGB marks the bearing as universally ground so that two or more can be assembled back-to-back with the intended preload arising from the grinding itself. The -1/2PR suffix identifies one bearing out of that pairing.

What these specs mean in practice

Contact angle decides the character of the bearing: 15° is the high-speed end of the range, carrying less thrust than a 25° bearing of the same envelope but generating less heat and running faster, and stiffer radially for a given preload. P4A class narrows bore, outside diameter, and radial and axial runout, which is what holds spindle runout inside a specification at speed. Universal grinding means any two bearings of this designation pair correctly without shims or measurement, and mounting them back-to-back sets the contact lines diverging outward from the shaft axis, giving a wide load span and high resistance to moment loads and shaft tilting.

Quantity and configuration

1 Pc. One bearing, universally ground for back-to-back pairing. Open both faces, straight bore.

Fitting notes

Super-precision bearings of this class expect a ground and measured shaft and housing seat, and are handled clean and mounted without heating or impact, with force applied through the ring being fitted rather than across the balls. The rings carry a wide face and a narrow face, and the direction the bearing goes in decides which way it takes thrust; on a paired mounting the outer-ring face marks are lined up so the ground offset closes as the set is clamped.

Interchange guidance

Same-envelope, same-angle super-precision equivalents are FAG B7209-C-T-P4S, NSK 7209CTR and Fafnir 2MM9209WI, all 45 x 85 x 19 mm at 15°. A 7209 ACD is 25° and a 7209 B is 40° in the same envelope, and a 7009 is the lighter 70 series at the same bore; those are related sizes rather than substitutions, because the angle changes both thrust rating and mounted stiffness.