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Two-row high-precision cylindrical roller bearings

Two-row cylindrical roller bearings are floating bearings. Mounting and dismounting is facilitated because they can be disassembled. Thus the rings can be fitted in firmly. Radial support of the main spindle of machine tools is the most important application for the bearing series NN30.. . NN means that the inner ring is provided with three guide flanges while the outer ring is without guide flanges. In addition, the standard design is provided with a conical bore (cone 1:12). Due to the conical bore it is possible to set the radial bearing clearance to optimum values. The outer ring is available with lubrication groove and lubrication bores on request. Lubrication is simplified in this way. The NNU49.. is also a two-row cylindrical roller bearing consisting of solid inner rings without guide flanges, solid outer rings with three guide flanges and can be dismantled.

Cages
The bearings of both series have two roller-guided solid brass cages each.

Heat treatment
The two-row cylindrical roller bearings have been heat treated such that they can be used up to an operating temperature of 150 °C. Bearings with an outer diameter of higher than 120 mm show dimensional stability up to 200 °C.

Tolerances
Due to their application, the cylindrical roller bearings are of high accuracy and have a specific tolerance class HP (high-precision, corresponds to tolerance class SP according to DIN 5412-4). Bearings with other tolerances are available on request.

Bearing clearance
The standard bearing clearance of the bearings is C1 (lower than standard clearance CN). Due to this bearing clearance it is not possible to exchange the bearings, i.e., the outer rings cannot be exchanged among the individual bearings as is the case, for instance, with single-row cylindrical roller bearings. Both C1 and NA (for not exchangeable) are not indicated.
Other radial clearance designs are available on request.

Norms
Two-row cylindrical roller bearings        DIN 5412-4

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NN30
NNU49
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