NSK Single-Direction Thrust Ball Bearings With Flat Seat , 51218 ,D=90
|Basic Load Ratings
DESIGN, TYPES, AND FEATURES
THRUST BALL BEARINGS
Thrust ball bearings are classified into those with flat seats or aligning seats, depending on the shape of the outer ring seat (housing washer). They can sustain axial loads but no radial loads.
Available Series of thrust ball bearings available are shown in Table 1.
For single-direction thrust ball bearings, pressed-steel cages and machined- brass cages are usually used as shown in Table 2. The cages in double- direction thrust ball bearings are the same as those in single-direction thrust ball bearings of the same Diameter Series.
The basic load ratings listed in the bearing tables are based on the standard cage type shown in Table 2. If the type of cage is different for bearings with the same number, the number of balls may vary; in such cases, the load rating will differ from that listed in the bearing tables
THRUST CYLINDRICAL ROLLER BEARINGS
These are thrust bearings containing cylindrical rollers. They can sustain only axial loads, but they are suitable for heavy loads and have high axial rigidity.
The cages are machined brass.
THRUST SPHERICAL ROLLER BEARINGS
These are thrust bearings containing convex rollers. They have a self- aligning capability and are free of any influence of mounting error or shaft deflection. Besides the original type, the E type with pressed cages for high load capacity is also available. Their bearing numbers are suffixed by E.
For horizontal shaft or high speed application, machined brass cages are recommended. For details, contact NSK.
Since there are several places where lubrication is difficult, such as the area between the roller heads and inner ring rib, the sliding surfaces between cage and guide sleeve, etc., oil lubrication should be used even at low speed.
The cages in the original type are machined brass.
DIMENSIONS RELATED TO MOUNTING
The dimensions related to mounting of thrust spherical roller bearings are listed in the Bearing Table.
If the bearing load is heavy, it is necessary to design the shaft shoulder with ample strength in order to provide sufficient support for the shaft washer.
The permissible misalignment of thrust spherical roller bearings varies depending on the size, but it is approximately 0.018 to 0.036 radian (1° to 2°) with average loads.
MINIMUM AXIAL LOAD
It is necessary to apply some axial load to thrust bearings to prevent slippage between the rolling elements and raceways.
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