Internal and operating clearance of INA plain bearings

Operating clearance of INA spherical plain bearings

The operating clearance or preload is determined on a fitted bearing still warm from operation.

It is derived from the radial internal clearance and the change in the radial internal clearance as a result of interference fit and thermal influences in the fitted condition.

Internal clearance of INA radial spherical plain bearings

The radial and axial internal clearance is determined on the dismounted bearing.

The radial internal clearance of radial spherical plain bearings is defined as the distance by which the inner ring can be moved in a radial direction relative to the outer ring from one extreme position to the precisely opposite extreme position.

Radial internal clearance of INA spherical plain bearings
Radial internal clearance of INA spherical plain bearings

INA maintenance-free spherical plain bearings

Maintenance-free spherical plain bearings have a very small internal clearance, see dimension tables. As a result, preloads may be present once the bearing is fitted.

INA spherical plain bearings requiring maintenance

The radial internal clearance is subdivided into three groups in accordance with DIN ISO 12240-1, see table. The precondition is a housing bore that causes no dimensional changes in the INA bearing with the exception of geometrical inaccuracies.

INA radial internal clearance

INA radial internal clearance groups

Internal clearance group in accordance with ISO 12240-1 Description Application range
Group N
(CN)
Normal internal clearance; CN is not included in bearing designations Under normal operating conditions and with the recommended fits, this gives optimum operating clearance
Group 2
(C2)
Internal clearance < CN (suffix C2) For bearing arrangements with very small clearance
Group 3
(C3)
Internal clearance > CN (suffix C3) For bearing rings with press fits or a large temperature differential between the inner and outer ring

INA radial internal clearance

Series Radial internal clearance
um
GE..-DO
GE..-DO-2RS(-2TS)
GE..-HO-2RS
GE..-LO
GE..-FO
GE..-FO-2RS(-2TS)
Group 2
(C2)
Group N
(CN)
Group 3
(C3)
Bore
d
mm
min. max. min. max. min. max.
6 6 8 32 32 68 68 104
8 8 8 32 32 68 68 104
10 10 8 32 32 68 68 104
12 - 8 32 32 68 68 104
- 12 10 40 40 82 82 124
15 15 10 40 40 82 82 124
16 - 10 40 40 82 82 124
17 17 10 40 40 82 82 124
20 - 10 40 40 82 82 124
- 20 12 50 50 100 100 150
25 25 12 50 50 100 100 150
30 30 12 50 50 100 100 150
32 - 12 50 50 100 100 150
35 - 12 50 50 100 100 150
- 35 15 60 60 120 120 150
40 40 15 60 60 120 120 180
45 45 15 60 60 120 120 180
50 50 15 60 60 120 120 180
60 - 15 60 60 120 120 180
- 60 18 72 72 142 142 212
63 - 18 72 72 142 142 212
70 70 18 72 72 142 142 212
80 80 18 72 72 142 142 212
90 - 18 72 72 142 142 212
- 90 18 85 85 165 165 245
100 100 18 85 85 165 165 245
110 110 18 85 85 165 165 245
120 120 18 85 85 165 165 245
140 - 18 85 85 165 165 245
160 140 18 100 100 192 192 284
180 160 18 100 100 192 192 284
200 180 18 100 100 192 192 284
- 200 18 110 110 214 214 318
220 220 18 110 110 214 214 318
240 - 18 110 110 214 214 318
250 240 18 125 125 239 239 353
260 260 18 125 125 239 239 353
280 280 18 125 125 239 239 353
300 - 18 125 125 239 239 353

Axial internal clearance

The axial internal clearance is defined as the distance by which the inner ring can be moved in an axial direction relative to the outer ring from one extreme position to the precisely opposite extreme position.

axial internal clearance of INA spherical plain bearings
Axial internal clearance

It is dependent on the bearing geometry and is in a direct relationship with the radial internal clearance. Depending on the bearing type, it may be several times greater than the radial internal clearance.

Fit conditions for INA spherical plain bearings

The interference fits and clearance fits for practical use are determined from the corresponding ISO fit in conjunction with the normal bearing tolerances in accordance with DIN ISO 12240-1 to DIN ISO 12240-3, see tables. The actual dimensions must correspond to the centre tolerance.

Definitions:
– indicates an interference fit
+ indicates a clearance fit.

Shaft fits

For example: A shaft of diameter 50 m6 has a probable interference fit of 0,023 mm.

Interference fit ÜI or clearance fit

Nominal shaft diameter in mm

over 3 6 10 18 30 50 80 120 180 250 315 400
incl. 6 10 18 30 50 80 120 180 250 315 400 500
Normal tolerance, interference fit or clearance fit in um(1
h6 0 0 +1 +1 +2 +2 +1 0 0 -2 -2 -2
j6 -6 -7 -7 -8 -9 -10 -13 -14 -17 -17 -20 -22
k6 -9 -9 -9 -14 -16 -20 -24 -28 -30 -33 -38 -42
m6 -12 -15 -17 -20 -23 -28 -34 -40 -47 -53 -59 -65
n6 -16 -19 -22 -27 -31 -37 -44 -52 -61 -67 -75 -82

1) Not applicable to series GE..-LO, GE..-PB, GE..-SX, GE..-PW and GE..-SW.

Housing fits

For example: A housing bore of diameter 75 M7 has a probable interference fit of 0,009 mm.

Interference fit ÜA or clearance fit

Nominal housing bore diameter in mm

over 6 10 18 30 50 80 120 150 180 250 315 400
incl. 10 18 30 50 80 120 150 180 250 315 400 500
Normal tolerance, interference fit or clearance fit in um1)
J7 +4 +5 +6 +7 +10 +12 +15 +18 +22 +27 +31 +34
K7 +1 +1 -1 0 0 -1 +1 +4 +5 +7 +8 +8
M7 -4 -5 -7 -8 -9 -11 -11 -8 -8 -9 -9 -10
N7 -8 -10 -14 -16 -18 -21 -23 -20 -22 -23 -25 -27

1) Not applicable to series GE..-SX and GE..-SW.

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