Internal Clearance and Standard Value
Internal clearance is the play between outer ring, inner ring and rolling element. Generally, the amount of up and down movement of the outer ring with respect to the fixed inner ring is called the radial internal clearance and its right and left movement the axial internal clearance. Bearing internal clearance in operation is an import factor that has a significant influence on other factors such as noise, vibration, hear and fatigue life. Radial ball bearings are usually classified by their internal radial clearance. When measuring the internal clearance, the bearing is subjected to a standard load in order to ensure full contact between all bearing components. Under such a load, the measured value is larger than the actual value stated for radial clearance; this is due to elastic deformation. The difference is compensated by the factors given in the tables below.
Radial Internal Clearance of Small and Miniature Bearings Unit: μm
Clearance
Mark |
MC1 |
MC2 |
MC3 |
MC4 |
MC5 |
MC6 |
Clearance |
max min |
max min |
max min |
max min |
max min |
max min |
0 5 |
3 8 |
5 10 |
8 13 |
13 20 |
20 28 |
Note: 1. Standard clearance is MC3
2. For measuring clearance offset by compensation factor listed below
Unit: μm
Clearance
Mark |
MC1 |
MC2 |
MC3 |
MC4 |
MC5 |
MC6 |
Compensation
Factor |
׀ |
׀ |
׀ |
׀ |
2 |
2 |
Measuring Load is as follows:
Miniature Bearings 25 N; Small Bearings 4.4N
Radial Internal Clearance of Standard Radial Ball Bearings Unit: μm
Nominal Bore Diameter
d (mm) |
Clearance |
C2 |
Standard |
C3 |
C4 |
C5 |
Over |
Incl. |
max min |
max min |
max min |
max min |
max min |
10(only)
10
18
24
30
40 |
18
24
30
40
50 |
- 7
- 9
- 10
1 11
1 11
1 11 |
2 13
3 18
5 20
5 20
6 20
6 23 |
8 23
11 25
13 28
13 28
15 33
18 36 |
14 29
18 33
20 36
23 41
28 46
30 51 |
20 37
25 45
28 48
30 53
40 64
45 73 |
Note: 1. For measuring clearance offset by compensation factor listed below
Unit: μm
Bore Diameter of
Normal Bearing d(mm) |
Measuring
Load
(N) |
Compensation Factor |
Over |
Incl. |
C2 |
Standard |
C3 |
C4 |
C5 |
10(included)
18 |
18
50 |
25.4
49 |
3 ~ 4
4 ~ 5 |
4
5 |
4
6 |
4
6 |
4
6 |
Selection of Bearing Clearance
Theoretically, maximum bearing life is with very slight preload. However, even a slight increase in this theoretical preload can have a considerably detrimental effect on the bearing life. Positive clearance should therefore be selected. MC3 is usually used for miniature or small bearings, standard clearance for general bearings and the clearance for thin section bearings should never be greater than “standard?br>
Selection of Radial Internal Clearance
Operating Condition |
Clearance |
Clearance fit for inner and outer ring. Low axial load. No axial load carrying requirement. Select bearing with reduced radial clearance. Lower vibration and noise. Low speeds. |
MC1,MC2,C2 |
Lower frictional torque. Standard axial load. Average axial load carrying requirements. Slight interference fit for inner ring. Clearance fit for outer ring. Average/low speed. |
MC2,MC4,STANDARD |
Extremely low frictional torque high axial load. High axial load carrying requirements. Heavy interference fit to support high loads or shock loads. Large temperature gradient from inner ring to outer ring. High degree of shat deflection |
MC5,MC6,C3 |
Radial Play
The radial play of a bearing has considerable influence on its performance. Therefore consideration must be given to the speed, temperature, load, adjacent materials (dissimilar coefficients of expansion) and fitting conditions associated with each individual application when selecting the appropriate group. The following notes are give for guidance against the various standard groups detailed in the Table below.
Miniature Bearings Below 10mm Bore
Service
Requirements |
Radial Play |
Suffix |
Remarks |
|
0.001 mm |
Small bearing clearance required axially without the use of preload shims or springs
Low torque not the prime requirement
High thrust loads will not occur |
Tight |
0 - 5
3 - 8 |
MC1
MC2 |
Interference fits must
be avoided
Beware differential
Expansion
Careful attention should be paid to any excessive
temperature rise in service |
Moderate torque
acceptable
Moderate thrust
Loads may occur |
Medium |
5 - 10
8 - 13 |
MC3
MC4 |
Interference fits are not
recommended |
Minimal torque
required
or
High thrust
load capacity |
Loose |
13 - 20
20 - 28 |
MC5
MC6 |
Moderate interference fits
can be applied
Axial play may require to be controlled by shims or springs |
Bearing over 10mm Bore
Unit: 0.001 mm
Bore (mm) |
Radial Clearance |
C2 |
Standard |
C3 |
C4 |
over below |
min max |
min max |
min max |
min max |
10 |
|
- |
7 |
2 |
13 |
8 |
23 |
14 |
29 |
10 |
18 |
- |
9 |
3 |
18 |
11 |
25 |
18 |
33 |
10 |
24 |
- |
10 |
5 |
20 |
13 |
28 |
20 |
36 |
|
|
|
|
|
|
|
|
|
|
24 |
30 |
- |
11 |
5 |
20 |
13 |
28 |
23 |
41 |
30 |
40 |
- |
11 |
6 |
20 |
15 |
33 |
28 |
46 |
40 |
50 |
- |
11 |
6 |
23 |
18 |
36 |
30 |
51 |
|
|
|
|
|
|
|
|
|
|
50 |
65 |
- |
15 |
8 |
43 |
23 |
43 |
38 |
61 |
65 |
80 |
- |
15 |
10 |
51 |
25 |
51 |
46 |
71 |
80 |
100 |
- |
18 |
12 |
58 |
30 |
58 |
53 |
84 |
100 |
120 |
- |
20 |
15 |
66 |
36 |
66 |
61 |
97 |
|