Preload - Precision RPM Inc.

Koyo Technical Information

8. Preload

Purpose and method of preload
Amount of preload — Matched pair angular contact ball bearings

b.1. S: slight preload
b.2. L: light preload
b.3. M: medium preload
b.4. H: heavy preload

a. Purpose and method of preload

1) Purposes of preloading

To improve bearing positioning accuracy in both the radial and axial directions and rotation accuracy by suppressing shaft deflection (vibration).
To improve gear engagement accuracy by increasing bearing rigidity.
To reduce the possibility of failure, such as smearing, by suppressing the sliding of rolling elements.
To prevent noise that may be caused by vibration and resonance.
Keep rolling elements in place with respect to the bearing rings.

2) Preloading methods

Bearings can be preloaded by the locating method or by the spring method. Typical preloading methods are given in the table.

When the size of the preload is the same, the locating method produces a smaller deflection in bearings than the spring method if the bearing is exposed to an axial load. This results in a high rigidity.
When the spring method is used, the spring absorbs load variation or shaft elongation and contraction, making it possible to apply the preload stably with minimum variation.
A greater preload is achievable when the locating method is used.

3)Typical preloading methods

Position preloading			Constant pressure preloading
Method using matched pair bearing with standout adjusted for preloading (see below).	Method using spacer with dimensions adjusted for preloading.	Method using nut or bolt capable of adjusting preload in axial direction. (In this case, starting friction moment during adjustment should be measured so that proper preload will be applied.)	Method using coil spring or diaphragm spring.

b. Amount of preload — Matched pair angular contact ball bearings

b.1. S: slight preload

Unit: N

Bore diameter No.	7900C	7000C	7200C
00 01 02	5 7 8	6 6 10	10 15 15
03 04 05	8 15 15	15 15 20	25 25 35
06 07 08	15 25 25	25 35 35	35 50 65
09 10 11	35 35 40	50 50 65	85 85 100
12 13 14	40 50 65	65 85 85	115 130 160
15 16 17	65 65 85	100 100 130	195 225 260
18 19 20	100 100 100	145 160 175	260 290 325
21 22 24	100 145 145	195 210 225	360 385 420
26 28 30	195 195 245	245 260 275	485 520 585
32 34	245 345	290 325	645 645

b.2. L: light preload

Unit : N

Bore diameter No.	7900C	7000	7000C	7200	7200C	ACT000	ACT000B
00 01 02	15 20 25	30 30 50	20 20 30	50 60 80	30 40 50	– – –	– – –
03 04 05	25 40 50	60 60 100	40 40 60	100 145 145	70 80 100	– – –	– – –
06 07 08	50 70 80	145 145 145	80 100 100	145 245 390	100 145 195	195 195 245	295 390 440
09 10 11	100 100 120	245 245 295	145 145 195	490 540 635	245 245 295	245 295 390	490 540 685
12 13 14	120 145 195	390 440 490	195 245 245	785 835 930	345 390 490	390 440 590	785 785 1030
15 16 17	195 195 245	590 635 735	295 295 390	980 1080 1270	590 685 785	590 685 735	1080 1270 1320
18 19 20	295 295 345	785 880 880	440 490 540	1470 1670 1860	785 880 980	980 980 1030	1770 1860 1910
21 22 24	345 390 490	980 1080 1180	590 635 685	2060 2250 2450	1080 1180 1270	1180 1320 1420	2150 2450 2550
26 28 30	590 635 735	1370 1470 1770	735 785 835	2750 2940 3330	1470 1570 1770	1770 2010 2400	3230 3720 4410
32 34	785 880	2150 2450	880 980	3630 3920	1960 2150	2500 3090	4660 5730

e. M: medium preload

Unit : N

Bore diameter No.	7900C	7000	7000C	7200	7200C	ACT000	ACT000B
00 01 02	30 40 50	80 80 145	50 50 80	145 145 245	80 100 145	– – –	– – –
03 04 05	50 80 100	145 145 245	100 100 145	245 295 390	145 195 245	– – –	– – –
06 07 08	100 140 155	295 390 390	195 245 295	590 785 880	295 390 440	345 390 440	685 735 835
09 10 11	195 195 235	540 635 785	345 390 440	1080 1180 1370	540 590 735	490 540 685	930 1030 1270
12 13 14	235 295 390	880 980 1080	490 540 635	1470 1670 1860	785 930 980	735 835 1130	1420 1520 2010
15 16 17	390 390 490	1180 1370 1570	685 735 880	2150 2450 2940	1180 1370 1570	1130 1370 1420	2110 2500 2600
18 19 20	590 590 685	1670 1770 1960	980 1080 1180	3230 3430 3920	1770 1960 2150	1860 1960 2010	3380 3530 3680
21 22 24	685 785 980	2150 2350 2650	1270 1470 1670	4310 4900 5390	2350 2450 2840	2250 2600 2800	3770 4760 5100
26 28 30	1180 1270 1470	3140 3430 3920	1770 1960 2150	5880 6370 6860	3140 3430 3720	3380 3920 4610	6230 7210 8480
32 34	1570 1810	4410 4900	2350 2450	7350 7840	4120 4410	4850 6030	8920 11100

f. H: heavy preload

Unit : N

Bore diameter No.	7000	7000C	7200	7200C
00 01 02	145 145 245	100 100 145	245 295 390	145 195 245
03 04 05	295 295 490	195 245 295	540 635 785	345 390 490
06 07 08	635 785 785	390 490 590	930 1270 1570	590 785 880
09 10 11	980 1180 1370	635 735 880	1770 2060 2450	1080 1180 1470
12 13 14	1570 1770 2060	980 1090 1270	2940 3330 3720	1670 1860 2060
15 16 17	2150 2350 2550	1370 1470 1770	3920 4310 4900	2350 2750 2940
18 19 20	2840 3140 3530	1960 2060 2150	5390 5880 6370	3430 3920 4410
21 22 24	3920 4410 4900	2350 2550 2840	7060 7840 8820	4900 5290 5490
26 28 30	5390 5880 6860	3140 3920 4410	9310 9800 10300	5880 6370 6860
32 34	7840 8820	4900 5390	10800 11800	7840 8330