FAGSuper-Precision Angular Contact Ball Bearing – 40 mm Bore, 80 mm OD, 18 mm Width, 15° Contact Angle, P4 Class, Light Preload

Product Description

What this part is

A FAG super-precision single-row angular contact ball bearing, 40 mm bore, 80 mm outside diameter, 18 mm width. Open, straight bore, phenolic laminate cage, P4 tolerance class, universally ground for light preload. The carton and ring carry several designations for the same bearing: 7208-TG-P4 in the older FAG scheme, B7208-C-TPA-P4-UL in the current Schaeffler scheme.

Decoding the designation

72 is the ISO dimension series and 08 the bore code, giving a 40 mm bore. The B prefix marks the super-precision spindle-bearing execution. C is a 15° contact angle. TG and TPA both denote the fabric-base phenolic laminate cage. P4 is the tolerance class, equivalent to ABEC 7. UL is the universal grinding with light preload: two bearings of this designation mounted back-to-back or face-to-face produce a defined light preload with no shimming, and any number can be stacked in tandem.

What these specs mean in practice

A 15° contact angle is the high-speed, low-thrust end of the angular contact range. It runs faster and cooler than a 25° or 40° bearing of the same envelope and carries correspondingly less axial load, which is why 15° super-precision bearings dominate machine tool spindle positions where surface speed and running accuracy matter more than thrust capacity. P4 class holds bore, outside diameter, width and running accuracy to super-precision limits, giving the low radial and axial runout a spindle needs.

Cage material and speed

The phenolic laminate cage is machined from cotton-fabric-reinforced phenolic resin. It is light, self-lubricating and outer-land or ball guided, which suits very high speed and oil-mist or oil-air lubrication. Phenolic sets a lower continuous temperature ceiling than brass and is not suited to grease-for-life operation at high temperature. The brass-cage counterpart of this envelope is designated with an M or MP cage code.

Quantity and configuration

1 Pc. Single bearing, supplied loose. The UL universal grinding means a second bearing of the same designation pairs with this one at the factory-defined light preload without ground spacers.

Mounting data

Bore form: straight, for an interference-fit spindle seat. Outer ring location: bored housing seat. Back-to-back (DB) arrangement: high shoulders of the outer rings face outward, giving the stiffest arrangement and the greatest moment capacity. Face-to-face (DF) arrangement: more tolerant of misalignment. Tandem (DT) arrangement: thrust capacity sums in one direction.

Interchange guidance

Timken/Fafnir 2MM208WI is the same 40x80x18 mm 15° super-precision envelope, its 2MM prefix denoting the 15° angle and P4S class. NSK 7208CTYNSULP4 and SKF 7208 CD/P4A are the same envelope, angle and class. Preload letter and cage material must match across a set. A 7208 in an A, A5, B or E execution carries a different contact angle, and a 7208 at P5 or P0 is a different tolerance class, so both are related sizes rather than interchanges.