Description
| Item # |
d |
D |
B |
r |
Static Load Rating |
Dynamic Load Rating |
| 51240 |
7.8740 in
200.000 mm |
11.0236 in
280.000 mm |
2.4409 in
62.000 mm |
0.0787 in
2.000 mm |
250000 lbf
1110000 N
1110.00 kN |
71000 lbf
315000 N
315.00 kN |
Thrust bearings are designed primarily to support axial loads at contact angles between 30° and 90°. Similar to radial bearings, thrust bearing designs may incorporate balls or rollers as rolling elements.
The configuration and characteristics of each type of bearing are given below.
With thrust bearings, it is necessary to supply an axial preload in order to prevent slipping between the bearing’s rolling elements and raceways.
For more detailed information, please refer to section “8.3 Bearing preload.”
1. Single direction thrust ball bearings
As shown in Fig. 1, the steel balls of single direction thrust ball bearings are arranged between a pair of a pair of washers (shaft washer and housing washer), and the normal contact angle is 90°. Axial loads can be supported in only one direction, and radial loads cannot be accommodated. These bearings are not suitable for high speed operation.
Table 1 lists the standard cage types for single direction thrust ball bearings
2. Thrust spherical roller bearings
Just like spherical roller bearings, the center of the spherical surface for thrust spherical roller bearings is the point where the raceway surface of the housing raceway washer meets the center axis of the bearing. Since thrust spherical roller bearings incorporate barrel-shaped rollers as rolling elements, they also have self-aligning properties. (See Fig. 2) Under normal load conditions, the allowable misalignment is 1/60 to 1/30, although this will vary depending upon the bearing’s dimension series.
These bearings use machined copper
alloy cages and a guide sleeve for the cage is attached to the inner ring. These bearings have a high axial load capacity, and can accommodate some radial load when the ring is axially loaded. It is necessary to operate these bearings where the load condition meets Fr / Fa ≦ 0.55.
The design for spherical thrust bearings is such that lubricant cannot enter the gap between the cage and the guide sleeve. Therefore, oil lubrication should be used, even in low speed operation.
3. Thrust cylindrical roller bearings
Thrust bearings incorporating cylindrical rollers are available in single row, double row, triple row, and four row varieties. (See Fig. 3) NTN Engineering offers the 811, 812 and 893 series that conform to dimension series 11, 12 and 93 prescribed in JIS, as well as other special dimensions.
While thrust cylindrical roller bearings are only able to receive axial loads, the axial loads can be heavy due to the high axial rigidity of the bearing. For series 811, 812, and 893, the dimension tables are listed section “E. Needle roller bearings.” Bearings with dimensions not listed in the dimension tables are also manufactured. Contact NTN Engineering for more information.
4. Thrust tapered roller bearings
Although not listed in the dimension tables, tapered roller bearings like those in Fig. 4 are also manufactured. Contact NTN Engineering for more detailed information.
