Machinery's Handbook, 31st Edition
2488
Ball and Roller Bearings Table 30. Values of X and Y for Computing Equivalent Thrust Load P a for Thrust Ball Bearings
Single Direction Bearings
Double Direction Bearings
F F
F F
F F
r a 2
r a
r a 2
e
e
e
Contact Angle α
#
X
Y 1 1 1
X
Y
X
Y 1 1 1
e
1.25 2.17 4.67
0.66 0.92 1.66
1.18 1.90 3.89
0.59 0.54 0.52
0.66 0.92 1.66
45 ° 60 ° 75 °
For α = 90 ° , F r = 0 and Y = 1. Roller Bearing Types Covered.— This standard* applies to cylindrical, tapered and self- aligning radial and thrust roller bearings and to needle roller bearings . These bearings are presumed to be within the size ranges shown in the AFBMA dimensional standards, of good quality and produced in accordance with good manufacturing practice. Roller bearings vary considerably in design and execution. Since small differences in relative shape of contacting surfaces may account for distinct differences in load- carrying ability, this standard does not attempt to cover all design variations, rather it ap- plies to basic roller bearing designs. The following limitations apply: 1) Truncated contact area. This standard may not be safely applied to roller bearings subjected to application conditions which cause the contact area of the roller with the raceway to be severely truncated by the edge of the raceway or roller. 2) Stress concentrations. A cylindrical, tapered or self-aligning roller bearing must be expected to have a basic load rating less than that obtained using a value of f c taken from Table 31 and Table 32 if, under load, a stress concentration is present in some part of the roller-raceway contact. Such stress concentrations occur in the center of nominal point contacts, at the contact extremities for line contacts and at inadequately blended junctions of a rolling surface profile. Stress concentrations can also occur if the rollers are not accurately guided such as in bearings without cages and bearings not having rigid integral flanges. Values of f c given in Table 31 and Table 32 are based upon bearings manufactured to achieve optimized contact. For no bearing type or execution will the factor f c be greater than that obtained in Table 31 and Table 32. 3) Material. This standard applies only to roller bearings fabricated from hardened, good quality steel. 4) Lubrication. Rating Life calculated according to this standard is based on the assump tion that the bearing is adequately lubricated. Determination of adequate lubrication depends upon the bearing application. 5) Ring support and alignment. Rating Life calculated according to this standard assumes that the bearing inner and outer rings are rigidly supported, and that the inner and outer ring axes are properly aligned. 6) Internal clearance. Radial roller bearing Rating Life calculated according to this standard is based on the assumption that only a nominal internal clearance occurs in the mounted bearing at operating speed, load, and temperature. 7) High-speed effects. The Rating Life calculated according to this standard does not account for high speed effects such as roller centrifugal forces and gyroscopic moments: These effects tend to diminish fatigue life. Analytical evaluation of these effects frequently requires the use of high-speed digital computation devices and hence, cannot be included. *Allreferencesto“standard”aretoAFBMAandAmericanNationalStandard“LoadRatingsandFatigue Life for Roller Bearings” ANSI/AFBMA Std 11-1990.
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