Koyo7905C5GLP4FGSuper-Precision Angular Contact Ball Bearing – 25 mm ID, 42 mm OD, 9 mm Width, 15 degree contact angle, Open, ABEC 7 / P4

Product Description

What this part is:

Koyo 7905C5GLP4FG is a single-row super-precision angular contact ball bearing in the metric 79 light series, bore 25 mm, outside diameter 42 mm, width 9 mm. The ISO base designation for this envelope is 71905. Rings and balls are through-hardened chrome steel, the bore is straight, and both faces are open for oil or grease feed.

Decoding the designation:

The 7905 root gives the 79-series dimension envelope on a 25 mm bore. The letter C is the Koyo contact-angle code for 15°. P4 is the running-accuracy class, equivalent to ABEC 7 in the ANSI scheme. The 5GL and FG groups are Koyo carton designations carried on this part; they are recorded under carton markings so the exact box number remains searchable.

What these specs mean in practice:

A 15° contact angle sets the load line close to the radial plane. That geometry favours speed and radial stiffness and carries less thrust than a 25° or 40° angle of the same size, which is why 15° bearings dominate machine tool and grinding spindles. The P4 class tightens bore, outside diameter and raceway runout well beyond a standard bearing, so shaft and housing seats have to be ground to matching tolerances for the accuracy to appear at the tool.

Quantity and configuration:

Single bearing, one row, universally ground faces. It runs alone as a bearing located in one axial direction, or in a ground stack with further bearings of the same designation for back-to-back, face-to-face or tandem duty.

Fitting notes:

Precision angular contact bearings are mounted with the high point of eccentricity indexed and the outer ring clamped square against a ground shoulder. Oil-air or oil-mist feed suits the open construction at high speed; light grease charge suits moderate speed. Handling is done clean, in the original wrap, with the axial faces protected.

Interchange guidance:

Crosses at 15° in the 71905 envelope, super-precision: Timken/Fafnir 2MM9305WI, SKF 71905 CD/P4A and FAG B71905-C-T-P4S. A 71905 or 7905 carrying a 25° angle code, a different cage, or a different preload group is a related size in the same envelope, because angle and preload set the stiffness and speed limit.