In the shaft system structure, there are usually three ways to fix rolling bearings:
1. Fixed at both ends: The inner rings of the two bearings are fixed by the shaft shoulder, and the outer rings are fixed by the flange cover; the inner and outer rings of each bearing are constrained in only one direction along the axial direction.
2. Fixed at one end and floating at one end: One support limits the bidirectional axial displacement of the shaft (called fixed support), and the other support can move axially (called floating support) and cannot bear axial load. Suitable for occasions with high working temperature and large pivot span.
3. Floating at both ends: For a single bearing, generally the inner ring and the outer ring need to be fixed. The outer ring of the bearing can be fixed with a retaining ring for the hole, and the inner ring can be fixed with a retaining ring for the shaft; both supports have no axial constraints, also known as floating supports at both ends. Commonly used in herringbone gear occasions to prevent the gear from getting stuck and uneven force on both sides of the herringbone gear.
Fixing of Rolling Bearings
A. Circumferential fixation
It can ensure that there is no relative circular motion between the inner ring and the journal, and the outer ring and the seat hole after the bearing is stressed.
Fixation is achieved by using the fit between the outer ring and the bearing seat hole, and the inner ring and the shaft neck;
The bearing is used as the reference part. The inner hole of the bearing and the shaft neck adopt the base hole system, and the outer diameter and the seat hole adopt the base shaft system;
The rotating ring is tighter than the fixed ring. The rotating seat ring should generally be guaranteed to have an interference, and the non-rotating seat ring should be guaranteed to have a clearance fit or transition fit with a smaller gap.
B. Axial fixation
Bearing inner ring fixation
1) Bearing shoulder fixation
The axial fixation of the bearing inner ring is achieved by using the shoulder and interference, which is mainly used for structures fixed at both ends.
2) Bearing elastic retaining ring fixation
The axial fixation of the bearing inner ring is achieved by the shoulder and locking nut, which can withstand a smaller bidirectional axial load.
3) Bearing locking nut fixation
The axial fixation of the bearing inner ring is achieved by the shoulder and locking nut, which is mostly used in high-speed and heavy-load working occasions.
4) Bearing end thrust washer fixation
The inner ring is axially fixed through the shaft shoulder and the shaft end retaining ring. The shaft end retaining ring is fixed to the shaft end with a screw with a loosening device; it is mainly used in working occasions where it is difficult or inappropriate to cut threads on the shaft end or where space is limited.
5) Bearing adapter sleeve fixation
The radial size of the inner hole of the adapter sleeve is compressed to clamp it on the shaft to achieve axial fixation of the inner ring.
6) Bearing withdrawal sleeve fixation
The withdrawal sleeve is usually equipped with a special nut, so it is more convenient to load and unload. It is used to fix the double-row spherical bearing on the optical axis.
Bearing outer ring fixation
1) Elastic retaining ring
Simple structure, easy installation and disassembly, small axial size, by adding an adjustment ring between the bearing end face and the retaining ring, the bearing axial position, assembly error and other adjustments can be achieved in working occasions with lower speed and smaller axial load.
2) Adjusting screw and adjusting cover
Similar to the end cover fixation, the adjusting screw device with anti-loosening measures can conveniently adjust the clearance of the outer bearing of the sight box.
3) Snap ring fixation
Fixed by the outer ring of the radial bearing with a snap groove, the structure is simpler and has a smaller axial size, but can only bear a smaller axial load.
4) End cover fixation
Commonly used in the fixation of radial or radial thrust bearings on the shaft end, the end cover has various forms. If a through hole form is adopted, multiple sealing devices can also be configured. It is more used in high speed and large axial load occasions.
5) Threaded ring fixation
Suitable for occasions with high speed and large axial load, the threaded ring with relaxation measures can adjust the clearance when the radial thrust bearing is installed face to face.
The clearance of the rolling bearing refers to the maximum movement of the inner and outer rings of the bearing, one of which is fixed and the other in the radial or axial direction, and is called radial clearance and axial clearance respectively.
| Radial clearance of deep groove ball bearings Unit: pm | |||||
| Nominal bearing inner diameter d (mm) | clearance | ||||
| C2 | CN | C3 | C4 | C5 | |
| ≤30 | 1~11 | 5~20 | 13~28 | 23~41 | 30~53 |
| >30~40 | 1~11 | 6~20 | 15~33 | 28~46 | 40~64 |
| >40~50 | 1~11 | 6~23 | 18~36 | 30~51 | 45~73 |
| >50~65 | 1~15 | 8~28 | 23~43 | 38~61 | 55~90 |
| >65~80 | 1~15 | 10~30 | 25~51 | 46~71 | 65~105 |
| >80~100 | 1~18 | 12~36 | 30~58 | 53~84 | 75~120 |
| >100~120 | 2~20 | 15~41 | 36~66 | 61~27 | 90~140 |
| >120~140 | 2~23 | 18~48 | 41~81 | 71~114 | 105~160 |
| >140~160 | 2~23 | 18~53 | 46~91 | 81~130 | 120~180 |
| >160~180 | 2~25 | 20~61 | 53~102 | 91~147 | 35~200 |
| >180~200 | 2~30 | 25~71 | 63~117 | 107~163 | 1 50~230 |
| >200~225 | 2~35 | 25~85 | 75~140 | 125~195 | 175~265 |
| >225~250 | 2~40 | 30~95 | 85~160 | 145~225 | 205~300 |
| >250~280 | 2~45 | 35~105 | 90~170 | 155~245 | 225~340 |
| >280~315 | 2~55 | 40~115 | 100~190 | 175~270 | 245~370 |
| >315~355 | 3~60 | 45~125 | 110~210 | 195~ 300 | 245~370 |
| >355~400 | 3~70 | 55~145 | 130~240 | 225~340 | 315~460 |
| >400~450 | 3~80 | 60~170 | I 50~270 | 250~380 | 350~510 |
| >450~ 500 | 3~90 | 70~190 | 170~300 | 280~420 | 390~570 |
| >500~560 | 10~100 | 80~210 | 190~330 | 310~470 | 440~630 |
| >560~630 | 10~110 | 90~230 | 210~360 | 340~520 | 490~690 |
| >630~710 | 20~130 | 110~260 | 240~ 400 | 380~772 | 540~760 |
| >710~800 | 20~140 | 120~290 | 270~450 | 430~630 | 600~840 |
| Radial internal clearance of self-aligning ball bearings Unit: (um) | ||||||||||
| Nominal bearing inner diameter d (mm) | Clearance of cylindrical bore bearings | Clearance of tapered bore bearings | ||||||||
| C2 | CN | C3 | C4 | C5 | CCI | CC2 | CC3 | CC4 | CC5 | |
| ≤30 | 5~16 | 11~24 | 19~35 | 29~46 | 40~58 | 9~20 | 15~28 | 23~39 | 33~50 | 44~62 |
| >30~40 | 6~18 | 13~29 | 23~40 | 34~53 | 46~66 | 12~24 | 19~35 | 29~46 | 40~59 | 52~72 |
| >40~50 | 6~19 | 14~31 | 25~44 | 37~57 | 50~71 | 14~27 | 22~39 | 33~52 | 45~65 | 58~79 |
| >50~65 | 7~21 | 16~36 | 30~50 | 45~69 | 62~88 | 18~32 | 27~47 | 41~61 | 56~80 | 73~99 |
| >65~80 | 8~27 | 18~40 | 35~60 | 54~83 | 76~108 | 23~39 | 35~57 | 50~75 | 69~98 | 91~123 |
| >80~100 | 9~27 | 22~48 | 42~70 | 64~96 | 88~124 | 29~47 | 42~68 | 62~90 | 84~116 | 109~144 |
| >100~120 | 10~31 | 25~56 | 50~83 | 75~114 | 105~145 | 35~66 | 50~81 | 75~108 | 100~139 | 130~170 |
| >120~140 | 10~38 | 30~68 | 60~100 | 90~135 | 125~170 | 40~68 | 60~98 | 90~130 | 120~165 | 155~205 |
| >140~160 | 15~44 | 35~80 | 70~120 | 110~161 | 150~210 | 45~74 | 65~110 | 100~150 | 140~191 | 180~240 |
| Axial clearance of radial thrust ball bearings, etc. (mm) | ||||||
| Bearing inner diameter | Axial clearance of radial thrust ball bearings | Clearance of single row tapered roller bearings | Double row thrust ball bearing axial clearance | |||
| Light Series | Medium and heavy series | Light Series | Light width, medium width and medium width series | Light Series | Medium and heavy series | |
| ≤30 | 0.02~0.06 | 0.03~0.09 | 0.03~0.1 | 0.04~0.11 | 0.03~0.08 | 0.05~0.11 |
| >30~50 | 0.03~0.09 | 0.04~0.10 | 0.04~0.11 | 0.05~0.13 | 0.04~0.10 | 0.06~0.12 |
| >50~80 | 0.04~0.10 | 0.05~0.12 | 0.05~0.13 | 0.06~0.15 | 0.05~0.14 | 0.07~0.14 |
| >80~120 | 0.05~0.12 | 0.06~0.15 | 0.06~0.15 | 0.07~0.18 | 0.06~0.15 | 0.10~0.18 |
| >120~150 | 0.06~0.15 | 0.07~0.18 | 0.07~0.18 | 0.09~0.20 | ||
| >150~180 | 0.07~0.18 | 0.09~0.20 | 0.09~020 | 0.10~0.22 | ||
| >180~200 | 0.09~020 | 0.10~0.22 | 0.12~0.22 | 0.14~0.24 | ||
| >200~250 | 0.18~0.30 | 0.18~0.30 | ||||
| Radial internal clearance of cylindrical roller bearings and tapered roller bearings Unit: (um) | |||||||||||
| Nominal bearing inner diameter d (mm) | Interchangeable clearance of cylindrical bore bearings | Non-interchangeable clearance of cylindrical bore bearings | |||||||||
| C2 | CN | C3 | C4 | C5 | CCI | CC2 | CC(1) | CC3 | CC4 | CC5 | |
| ≤30 | 0~25 | 20~45 | 35~60 | 50~75 | 70~95 | 5~15 | 10~25 | 25~35 | 40~50 | 50~60 | 70~80 |
| >30~40 | 5~35 | 25~50 | 45~70 | 60~85 | 80~105 | 5~15 | 12~25 | 25~40 | 45~33 | SS~70 | 80~95 |
| >40~50 | 5~35 | 30~60 | 50~80 | 70~100 | 95~125 | 5~18 | 15~30 | 30~45 | 50~65 | 65~808 | 95~110 |
| >50~63 | 10~40 | 40~70 | 60~90 | 80~110 | 10~140 | 5~20 | 15~33 | 35~50 | 55~75 | 75~90 | 10~130 |
| >65~80 | 10~45 | 40~75 | 65~100 | 90~125 | 130~165 | 10~25 | 20~40 | 40~60 | 70~90 | 90~110 | 130~150 |
| >80~100 | 15~80 | 50~85 | 75~110 | 105~140 | 155~190 | 10~30 | 23~45 | 45~70 | 80~105 | 105~125 | 155~180 |
| >100~120 | 15~55 | 50~90 | 85~125 | 125~165 | 180~220 | 10~30 | 25~50 | 50~80 | 95~120 | 120~145 | 180~205 |
| >120~140 | 15~60 | 60~105 | 100~140 | 145~190 | 200~245 | 10~33 | 30~60 | 60~90 | 105~135 | 135~160 | 200~230 |
| >140~160 | 20~70 | 80~120 | 5~165 | 165~215 | 225~275 | 10~35 | 35~65 | 65~100 | 115~150 | 150~180 | 225~260 |
| >160~180 | 25~75 | 75~125 | 120~170 | 170~220 | 250~300 | 10~40 | 35~75 | 75~110 | 125~165 | 165~200 | 220~185 |
| >180~200 | 35~90 | 90~145 | 140~195 | 195~250 | 275~330 | 15~45 | 40~80 | 80~120 | 140~180 | 180~220 | 275~315 |
| >200~225 | 45~105 | 105~165 | 160~220 | 220~280 | 305~365 | 15~50 | 45~90 | 90~135 | 135~200 | 200~240 | 305~350 |
| >225~250 | 45~110 | 10~173 | 170~235 | 235~300 | 330~399 | 15~50 | 50~100 | 100~150 | 170~1215 | 215~265 | 330~ 380 |
| >250~280 | 55~125 | 125~195 | 190~260 | 260~330 | 370~440 | 20~55 | 55~10 | 110~165 | 185~240 | 240~295 | 370~420 |
| >280~315 | 65~130 | 130~205 | 200~275 | 275~350 | 410~485 | 20~60 | 60~120 | 120~180 | 205~265 | 265~325 | 410~470 |
| >315~355 | 65~145 | 145~225 | 225~305 | 305~385 | 455~535 | 20~65 | 65~135 | 135~200 | 225~295 | 295~360 | 455~520 |
| >355~400 | 100~195 | 190~280 | 280~370 | 370~460 | $10~600 | 25~75 | 75~150 | 150~225 | 235~330 | 330~405 | 510~585 |
| >400~450 | 110~210 | 210~310 | 310~410 | 410~510 | 365~663 | 25~88 | 85~170 | 170~255 | 255~370 | 370~445 | 445~650 |
| >450~500 | 110~220 | 220~330 | 330~440 | 440~550 | 625~735 | 25~95 | 95~190 | 190~285 | 315~410 | 410~505 | 625~720 |
| Axial clearance value of double row tapered roller bearing during assembly (mm) | ||
| Bearing inner diameter | General situation | The inner ring temperature is 25~30℃ higher than the outer ring temperature |
| <80 | 0.10~020 | 0.30~0.40 |
| >80~180 | 0.15~025 | 0. 40~0.50 |
| >180~225 | 0.20~0.30 | 0.50~0.60 |
| >225~315 | 0.30~0.40 | 070~0.90 |
| >315~560 | 0.40~0.50 | 0.90~1 |
| Axial clearance value of four~row tapered roller bearing during assembly (mm) | |||
| Bearing inner diameter | Axial clearance | Bearing inner diameter | Axial clearance |
| >120~180 | 0.15~025 | >560~630 | 0.30~0 40 |
| >180~225 | 0.20~0.30 | >630~800 | 0.35~0.45 |
| >225~315 | 025~035 | >800~1000 | 0.34~0.45 |
| >315~560 | 0.30~0 40 | >1000~1250 | 0. 40~0.50 |
The rolling bearing should have the necessary clearance to compensate for the manufacturing and assembly deviations, thermal expansion, and the formation of oil film to ensure its uniform and flexible movement, otherwise blocking will occur. However, excessive clearance will concentrate the load, generate impact and vibration, not only generate noise during work, but also cause serious friction, wear, heat, and even cause accidents. Therefore, choosing the appropriate clearance is one of the important links to ensure the normal operation of the bearing and extend its service life.
The preload of rolling bearings refers to maintaining a certain initial pressure and elastic deformation between the rolling elements and the rings inside the bearing during assembly to reduce the actual deformation of the bearing under the working load, thereby improving the support stiffness, improving the rotation accuracy, and improving the vibration resistance of the system due to a certain damping.
| Minimum preload for positioning preload Fa0 min | |||
| Bearing type | Pure axial load FA | Combined radial and axial loads FA, Fr | Note |
| Angular contact bearings | 0.35FA | 1.7 Fr tana± Fa/2 | When FA and the bearing load direction are the same, the sign is negative, when they are opposite, the sign is positive |
| Tapered roller bearings | 0.5FA | 1.9 Fr tana± Fa/2 | When FA and the bearing load direction are the same, the sign is negative, when they are opposite, the sign is positive |
| Note: Fr is the radial load carried by the bearing (kN), a is the contact angle of the bearing | |||
The preload of the bearing is divided into axial preload and radial preload. The radial preload is generally adjusted by axial displacement of the inner ring of the tapered hole and the matching tapered neck or by increasing the interference between the shaft and the bearing hole; the axial preload is adjusted by gaskets, spacers, springs, nuts or threaded end caps.
