Double-row cylindrical roller bearings are commonly available in the following types: NN type double-row cylindrical roller bearings, NN…K type double-row cylindrical roller bearings with tapered inner, NNU type double-row cylindrical roller bearings without inner-ring ribs, and NNU…K type double-row cylindrical roller bearings with tapered inner and without inner-ring ribs.

Among them, the NN type has ribs on both sides of the inner ring, which are inseparable from the rollers, while the outer ring has no ribs. This design allows the outer ring to move freely in both axial directions. The NNU type has ribs on both sides of the outer ring, which are inseparable from the rollers, while the inner ring has no ribs. This design allows the inner ring to move freely in both axial directions.

The NN…K type and NNU…K type adopt a tapered inner design on the inner ring, with the inner diameter gradually decreasing along the axial direction, forming a conical structure. They are usually used together with adapter sleeves or withdrawal sleeves. Although the tapered inner design makes installation more complex, it provides better axial positioning and adjustment performance, making it suitable for applications with higher requirements for axial positioning and adjustment.

Double-row cylindrical roller bearings feature a compact structure, high rigidity, large load-carrying capacity, and minimal deformation under load. They are particularly suitable for use in machine tool spindle supports.