NSK 638 ZZ1MC3 (ZZ) Kugellager (8x28x9)

This NSK bearing measures 8x28x9 mm and weighs 0.028 kg; the specification table carries the supplementary technical details. Point contact between ball and raceway keeps frictional torque low, which is why this type runs faster and cooler than any other rolling bearing. The deep, closely conforming raceway grooves in the inner and outer ring capture the balls positively, so the bearing takes radial load and moderate axial load in both directions without a second bearing position to oppose it.

Because the ball touches the raceway at a point, friction and heat stay low — the precondition for high speeds and for grease-for-life designs. The limits follow from that same geometry: the small contact area caps load capacity against a roller bearing of equal size, and the bearing tolerates misalignment within narrow limits only, since angular error transfers straight into the raceway grooves.

Seats in shaft and housing must therefore be aligned and geometrically accurate; where shaft deflection is expected, a self-aligning type belongs in that position. The shields on both sides run without contact: they hold back coarse contamination and keep the lubricant in, adding no frictional torque — but they do not protect against splash water or fine dust.

Rings and rolling elements are made of through-hardened standard bearing steel. The normal radial clearance recorded corresponds to the standard class and suits ordinary fits and temperature conditions.