Two-row cylindrical roller bearings are floating bearings. Mounting and dismounting is easy because they can be dismantled, so the rings can be fitted tightly.
Radial support of machine tool main spindles is the most important application of the NN30.. series. NN means that the inner ring has three guide flanges while the outer ring has none. The standard design has a tapered bore (taper 1:12), allowing the radial clearance to be set to optimum values. The outer ring is available with lubrication groove and holes on request.
The NNU49.. is also a separable two-row cylindrical roller bearing with solid inner rings without flanges and solid outer rings with three guide flanges.