– 16 –
(7) Bearing clearance
When purchasing bearings from a bearing manufacturer, order the type with the bearing No. noted on the motor
nameplate. Observe the following points when placing the order.
a. Clarification of clearance symbol
The bearing clearance is very important for the bearing life, noise and vibration. Thus, when purchasing the
bearings, the clearance symbol must be clearly instructed in addition to the basic bearing No. (e.g. 6310, NU314,
etc.) and shielded symbol (e.g. ZZ, etc.). General motors use bearings with a special clearance to suppress
noise and vibration. This clearance is indicated with the symbol "CM". The relation of each clearance is shown
in Table 14. If a special clearance is used, it is indicated on the motor nameplate. However, the "CM" clearance
symbol is abbreviated.
When placing your order, indicate the "motor" or "CM" clearance symbol (e.g.
6310ZZ or 6310ZZCM for motor).
Table 14-1 Radial internal clearance of deep groove ball bearings
(Unit: 0.001mm)
Nominal dimension of
bearing bore diameter
(mm)
Clearance
C2
Normal
CM
C3
C4
More than
(
<
)
Less than
(
≥
)
Min.
Max.
Min.
Max.
Min.
Max.
Min.
Max.
Min.
Max.
10
18
24
30
40
50
65
18
24
30
40
50
65
80
–
–
–
–
–
–
–
9
10
11
11
11
15
15
3
5
5
6
6
8
10
18
20
20
20
23
28
30
4
5
5
9
9
12
12
11
12
12
17
17
22
22
11
13
13
15
18
23
25
25
28
28
33
36
43
51
18
20
23
28
30
38
46
33
36
41
46
51
61
71
[Remarks] When using the clearance as the measurement clearance, the clearance compensation amount is as follows to compensate the increase
in the radial clearance cause by the measurement load. The smaller of the C2 clearance compensation amounts is used for the min.
clearance and the larger is used for the max. clearance.
Nominal dimension of
bearing bore diameter
(mm)
Measurement
load
(N)
Compensation amount of radial internal clearance
More than
(
<
)
Less than
(
≥
)
C2
Normal and CM
C3
C4
10
(inclusive)
18
24.5
3 to 4
4
4
4
18
50
49
4 to 5
5
6
6
50
280
147
6 to 8
8
9
9
Table 14-2 Internal radial clearances of roller bearings (with cylindrical holes not interchangeable)
(Unit: 0.001mm)
Nominal dimension of
bearing bore diameter
(mm)
Internal radial clearances
C2
CM
Normal
C3
C4
C5
More than
(
<
)
Less than
(
≥
)
Min.
Max.
Min.
Max.
Min.
Max.
Min.
Max.
Min.
Max.
Min.
Max.
80
100
25
45
35
55
45
70
80
105
105
125
155
180