Koyo7907-5GL-P4Super Precision Angular Contact Ball Bearing 35x55x10 mm ABEC 7 Light Preload Universally Ground

Product Description

What this part is

A single row super precision angular contact ball bearing in the 79xx extra-light spindle series, 35 mm bore, 55 mm outside diameter, 10 mm width, held to P4 tolerance. The 79 series is the thinnest section in the spindle bearing range, chosen where radial space is tight and where a short, stiff bearing set is wanted close to the tool or workpiece. The equivalent ISO designation for this envelope is 71907.

Decoding the designation

In the Koyo scheme 7907 places the bearing in the 79 extra-light angular contact series at bore code 07, giving the 35 mm bore. GL is the light preload class. P4 is the tolerance class, equivalent to ABEC 7 — controlled bore and outside diameter tolerance, and controlled radial and axial runout. The bearing is universally ground, so any two pieces of the same designation can be assembled as a matched pair in back-to-back, face-to-face or tandem arrangement without shims and will take up the nominal preload automatically.

What these specs mean in practice

Angular contact geometry puts the ball contact on a line inclined to the radial plane, so the bearing carries radial load together with axial load in one direction, and a pair mounted opposed carries axial load in both. Light preload is the class chosen for high-speed spindle work: preload removes internal clearance and raises stiffness and running accuracy, and the light class keeps the resulting frictional heat and speed penalty at a minimum. Heavier preload buys stiffness and costs speed and heat.

Precision class

P4 corresponds to ABEC 7 in the ANSI/ABMA scheme. Compared with P5 / ABEC 5 it tightens bore, outside diameter, width and runout, and it is the standard class for machine tool spindles, grinding heads, high-speed rotary tables and precision gearbox input positions.

Quantity and configuration

1 Pc. Single bearing, open on both faces, with no seals, shields or snap ring. Supplied without a spacer set, lock nut or preload sleeve.

Fitting notes

Super precision bearings are handled clean and mounted with even axial force on the ring being pressed, never through the balls. Where two pieces are being paired the marked faces are set according to the intended arrangement, and the shaft and housing seats are held within the tolerance grade appropriate to a P4 bearing, since seat error transfers directly into spindle runout at this class.

Interchange guidance

The 35 x 55 x 10 mm envelope in this class is served across the super precision makers: NSK 7907, NTN 7907, FAG B71907, SKF 71907 CD and Fafnir 2MM9307WI in the same size. Contact angle and preload class are part of the specification and are not interchangeable between designations — a same-envelope bearing at a different contact angle or preload class is a related size rather than a substitution. Tolerance class is likewise part of the specification: a P5 version of this bearing is a different part.