SKF7208CP4GAngular Contact Ball Bearing – Straight Bore, 40mm ID, 80mm OD, 18mm Width, Open, Phenolic Cage, 15° Contact Angle, High Precision P4.

Product Description

What this part is

SKF 7208 C P4G single-row super-precision angular contact ball bearing, 40 mm bore, 80 mm outside diameter, 18 mm width. Straight bore, open on both faces, phenolic cage, 15° contact angle, ABEC 7 running accuracy.

Decoding the designation

The 7200 series is the light angular contact dimension series and the bore code 08 denotes 40 mm, the bore code multiplied by five. In the SKF scheme C is the 15° contact angle and P4 is the ISO precision class equivalent to ABEC 7. The Fafnir designation for the same bearing is 2MM208WI, where the 2MM prefix likewise marks a 15° angle.

What these specs mean in practice

A 15° contact angle keeps the ball load line close to radial, which limits centrifugal loading of the contact and raises the speed ceiling: this bearing is rated to 30000 rpm on oil. That is the reason 15° is the machine tool spindle standard where a 25° or 40° angle would be chosen for axial stiffness instead. Basic dynamic capacity is 33.8 kN and static capacity 24 kN.

Cage and precision

The phenolic cage is a fabric-reinforced laminate: light, self-lubricating and quiet, and the standard choice for high-speed spindle service. ABEC 7 holds bore, outside diameter and raceway runout to a small fraction of a standard-class bearing, which is what allows a spindle to hold a tight geometric tolerance at speed.

Quantity and configuration

One piece, single bearing, universally matchable so two may be arranged back to back, face to face or in tandem.

Fitting notes

Super-precision bearings are mounted clean and by controlled means, with force applied to the ring being fitted. Thrust is taken on the high-shoulder side, so a single bearing is oriented to the direction of axial load, and each ring is seated square against its abutment before a locknut is drawn up.

Interchange guidance

Direct equivalents at the same envelope, angle and class include the Fafnir 2MM208WI, the FAG B7208-C-T-P4S and the NSK 7208CTYNSULP4. A 7208 at 25° or 40° is a related size: same 40 x 80 x 18 mm envelope, different thrust and speed behaviour. A Fafnir 2MM9108WI belongs to the extra-light 79nn series and is a different envelope.