Page 47 - NSK_CAT_E1102m_A7-141

PRELOAD

10.4.2 Amount of Preload Table 10. 1 Recommended Fitting for (2) Preload of Thrust Ball Bearings (3) Preload of Spherical Thrust Roller Bearings
High Accuracy Duplex
If the preload is larger than necessary, abnormal heart Angular Contact Ball When the balls in thrust ball bearings rotate at relatively When spherical thrust roller bearings are used, damage
generation, increased frictional torque, reduced fatigue Bearings with Preload high speeds, sliding due to gyroscopic moments on the such as scoring may occur due to sliding between the
life, etc. may occur. The amount of the preload should balls may occur. The larger of the two values obtained rollers and outer ring raceway. The minimum axial load
be carefully determined considering the operating from Equations(10.1) and (10.2) below should be Fa min necessary to prevent such sliding is obtained
conditions and the purpose of the preload. adopted as the minimum axial load in order to prevent from the following equation:
such sliding
(1) Preloading of Duplex Angular Contact Ball Units : μ m
Bearings C0a
Nominal Bore Nominal Outside C0a n 2 . . . . . . . . . . . . . . . . . . . . . . . .(10.1) Fa min = 1000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (10.3)
Average preloads for duplex angular contact ball Dia. 100
bearings (contact angle of 15°) with precision better Dia. d (mm) Nmax
than P5 class, which are used on the main shafts of Target Shaft D (mm) Target ( )Fa min =
machine tools, are listed in Table 10.2. over incl. Interference Housing
The recommended fitting between the shaft and inner over incl. Clearance
ring and between the housing and outer ring are listed C0a
in Table 10.1. In the case of fits with housings, the ⎯ 18 0 to 2.5 ⎯ 18 ⎯ Fa min = 1000 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . (10.2)
lower limit of the fitting range should be selected for
fixed-end bearings and the upper limit for free-end 18 30 0 to 2.5 18 30 2 to 6
bearings.
As a general rule, an extra light or light preload should 30 50 0 to 2.5 30 50 2 to 6 where Fa min : Minimum axial load (N), {kgf}
be selected for grinding spindles and the main shafts
of machining centers, while a medium preload should 50 80 0 to 3.5 50 80 3 to 8 n : Speed (min–1)
be adopted for the main shafts of lathes requiring 80 120 0 to 4.5 80 120 3 to 9
rigidity. 120 150 120 150 4 to 12 C 0a : Basic static load rating (N), {kgf}
⎯ Nmax : Limiting speed (oil lubrication) (min–1)
When speeds result in a value of Dpw× n (dmn value)
150 180 ⎯ 150 180 4 to 12
higher than 500000, the preload should be very 180 250 ⎯ 180 250 5 to 15
carefully studied and selected. In such a case, please
consult with NSK beforehand. Table 10. 2 Preloads for Duplex Angular Contact Ball Bearings
Table 10. 2. 2 Duplex
Table 10. 2. 1 Duplex Bearings of Series 79 Bearings of Series 70 Table 10. 2. 3 Duplex Bearings of Series 72
Preloads
Units : N Units : N Units : N

Preloads Heavy Preloads Heavy
Preload H Preload H
Bearing Extra light Light Medium Bearing Extra light Light Medium Heavy Bearing Extra light Light Medium
No. Preload EL Preload L Preload M 59 No. Preload EL Preload L Preload M Preload H No. Preload EL Preload L Preload M 150
78 200
7900 C 7 15 29 100 7000 C 12 25 49 100 7200 C 14 29 69 200
7901 C 8.6 15 39 7001 C 12 25 59 120 7201 C 19 39 100
7902 C 12 25 49 120 7002 C 14 29 69 150 7202 C 19 39 100 290
150 390
7903 C 12 25 59 200 7003 C 14 29 69 150 7203 C 24 49 150 390
7904 C 19 39 78 7004 C 24 49 120 250 7204 C 34 69 200
7905 C 19 39 100 200 7005 C 29 59 150 290 7205 C 39 78 200 590
290 780
7906 C 24 49 100 390 7006 C 39 78 200 390 7206 C 60 120 290 980
7907 C 34 69 150 7007 C 60 120 250 490 7207 C 75 150 390
7908 C 39 78 200 390 7008 C 60 120 290 590 7208 C 100 200 490 1 080
490 1 180
7909 C 50 100 200 590 7009 C 75 150 340 690 7209 C 125 250 540 1 570
7910 C 50 100 250 7010 C 75 150 390 780 7210 C 125 250 590
7911 C 60 120 290 590 7011 C 100 200 490 980 7211 C 145 290 780 1 860
690 2 160
7912 C 60 120 290 980 7012 C 100 200 540 1 080 7212 C 195 390 930 2 350
7913 C 75 150 340 7013 C 125 250 540 1 080 7213 C 220 440 1 080
7914 C 100 200 490 980 7014 C 145 290 740 1 470 7214 C 245 490 1 180 2 450
980 2 750
7915 C 100 200 490 1 270 7015 C 145 290 780 1 570 7215 C 270 540 1 230 3 330
7916 C 100 200 490 7016 C 195 390 930 1 860 7216 C 295 590 1 370
7917 C 145 290 640 1 470 7017 C 195 390 980 1 960 7217 C 345 690 1 670 3 730
1 570 4 120
7918 C 145 290 740 1 770 7018 C 245 490 1 180 2 350 7218 C 390 780 1 860 4 710
7919 C 145 290 780 7019 C 270 540 1 180 2 350 7219 C 440 880 2 060
7920 C 195 390 880 7020 C 270 540 1 270 2 550 7220 C 490 980 2 350

A 98 A 99