NSK 689 UMC3 (CN/C0) Kugellager (9x17x4)

For this NSK bearing, 9x17x4 mm and a weight of 0.004 kg apply; the specification table holds the further technical particulars. 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 open version leaves sealing, initial filling and relubrication to the surrounding design, while keeping the rolling chamber accessible for a directed supply of lubricant. 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.