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FITS AND INTERNAL CLEARANCES

9.2 Bearing Internal Clearances To obtain accurate measurements, the clearance is Table 9.9 Radial Internal Clearances in Table 9.10 Radial Internal Clearances in Extra
generally measured by applying a specified measuring Deep Groove Ball Bearings Small and Miniature Ball Bearings
9.2.1 Internal Clearances and Their Standards load on the bearing; therefore, the measured clearance
(sometimes called “measured clearance” to make a Units : μ m Units : μ m
The internal clearance in rolling bearings in operation distinction) is always slightly larger than the theoretical
greatly influences bearing performance including internal clearance (called “geometrical clearance” for Nominal Bore C2 Clearance C5 Clear-
fatigue life, vibration, noise, heat-generation, etc. radial bearings) by the amount of elastic deformation Diameter CN C3 C4 ance MC1 MC2 MC3 MC4 MC5 MC6
Consequently, the selection of the proper internal caused by the measuring load. Symbol
clearance is one of the most important tasks when Therefore, the theoretical internal clearance may be d (mm)
choosing a bearing after the type and size have been obtained by correcting the measured clearance by the min. max. min. max. min. max. min. max. min. max. min. max.
determined. amount of elastic deformation. However, in the case over incl. min. max. min. max. min. max. min. max. min. max. Clear-
This bearing internal clearance is the combined of roller bearings this elastic deformation is negligibly ance 0 5 3 8 5 10 8 13 13 20 20 28
clearances between the inner/outer rings and rolling small. 10 only 07 2 13 8 23 14 29 20 37
elements. The radial and axial clearances are defined Usually the clearance before mounting is the one 10 18 09 3 18 11 25 18 33 25 45 Remarks 1. The standard clearance is MC3.
as the total amount that one ring can be displaced specified as the theoretical internal clearance. 18 24 0 10 5 20 13 28 20 36 28 48 Remarks 2. To obtain the measured value, add
relative to the other in the radial and axial directions In Table 9.8, reference table and page numbers are
respectively (Fig. 9.1). listed by bearing types. correction amount in the table below.

24 30 1 11 5 20 13 28 23 41 30 53 Units : μ m
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 Clearance MC1 MC2 MC3 MC4 MC5 MC6
65 80 1 15 10 30 25 51 46 71 65 105 Symbol
80 100 1 18 12 36 30 58 53 84 75 120
Clearance
100 120 2 20 15 41 36 66 61 97 90 140 Correction 1 1 1 1 2 2
120 140 2 23 18 48 41 81 71 114 105 160
Table 9.8 Index for Radial Internal Clearances 140 160 2 23 18 53 46 91 81 130 120 180 Value
by Bearing Types
160 180 2 25 20 61 53 102 91 147 135 200 The measuring loads are as
Bearing Types Table Page 180 200 2 30 25 71 63 117 107 163 150 230 follows :
Number Number 200 225 2 35 25 85 75 140 125 195 175 265
For miniature ball bearings*
Deep Groove Ball Bearings 9.9 A89 225 250 2 40 30 95 85 160 145 225 205 300 2.5N {0.25kgf}
250 280 2 45 35 105 90 170 155 245 225 340
280 315 2 55 40 115 100 190 175 270 245 370 For extra small ball bearings*
4.4N {0.45kgf}

*For their classification, refer to
Table 1 on Page B 31.

Extra Small and Miniature Ball Bearings 9.10 A89

Magneto Bearings 9.11 A89 315 355 3 60 45 125 110 210 195 300 275 410 Table 9.11 Radial Internal Clearances in
355 400 3 70 55 145 130 240 225 340 315 460 Magneto Bearings
400 450 3 80 60 170 150 270 250 380 350 510
Units : μ m
Self-Aligning Ball Bearings 9.12 A90 450 500 3 90 70 190 170 300 280 420 390 570
A90 500 560 10 100 80 210 190 330 310 470 440 630
Deep Groove 9.13.1 A90 560 630 10 110 90 230 210 360 340 520 490 690 Nominal Bore Bearing Clearance
Ball Bearings 9.13.2 Diameter Series min. max.
A91 630 710 20 130 110 260 240 400 380 570 540 760
Radial Clearance Axial Clearance For Motors 9.14 710 800 20 140 120 290 270 450 430 630 600 840 d (mm)
Cylindrical A92
Roller Bearings A93 over incl.
A94
With Cylindrical Bores A94 Remarks To obtain the measured values, use the clearance correction for EN 10 50
Remarks radial clearance increase caused by the measuring load in the E 30 60
Table 9.8 Bearing Internal Clearance With Cylindrical Bores table below. 2.5 30
(Matched) For the C2 clearance class, the smaller value should be used
Cylindrical for bearings with minimum clearance and the larger value for
Roller Bearings bearings near the maximum clearance range.

With Tapered Bores

(Matched)

Spherical With Cylindrical Bores 9.15

Roller Bearings With Tapered Bores Units : μ m

Double-Row and Combined Tapered 9.15 Nominal Bore Measuring Radial Clearance Correction
Roller Bearings 9.17 Load Amount
9.18 Dia. d (mm)
Combined Angular Contact Ball (N) {kgf} C2 CN C3 C4 C5
Bearings (1) over incl.

Four-Point Contact Ball Bearings (1) 10 (incl) 18 24.5 {2.5} 3 to 4 4 4 4 4
18 50 49 {5} 4 to 5 5 6 6 6
Note (1) Values given are axial clearances. 50 280 147 {15} 6 to 8 8 9 9 9

Remarks For values exceeding 280 mm, please contact NSK.

A 88 A 89