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Internal Clearance

Internal clearance is the play within a ball bearing. It is the geometrical clearance between the inner ring, outer ring and ball. It is a critical factor in bearing selection that will directly impact bearing life. It is often overlooked, particularly as to how it is reduced by interference fits.

Radial clearance is the play between the ball and raceway perpendicular to the bearing axis. Axial clearance is the play parallel to the bearing axis and is typically at least 10 times greater than the radial clearance. Generally, internal radial clearance will be reduced 80% of the interference fit amount.

Too little or too much internal clearance will significantly influence factors such as heat, vibration, noise, and fatigue life.

In extreme applications that see high or low temperatures this clearance needs to be considered in the overall design to compensate for thermal expansion and contraction of housings and shafts.

Selecting Bearing Clearance (General guidelines)
Operating Condition Clearance
Clearance fit on both inner and outer ring. Low to no axial loading. No preload. Low speeds. Little tolerance for play. Low temperature. C2
Low torque. Standard loads. Light preload. Slight interference fit on inner or outer ring, not both. Low to medium speeds. Average temperature. CN
Very low torque. High loads. Heavy interference fits. High temperature. Preloaded. C3,C4,C5

Deep Groove Ball Bearing Radial Internal Clearance (Units: µm)
Nominal Bore Diameter
(mm)
Clearance
C2 CN
(NORMAL)
C3 C4 C5
over incl min max min max min max min max min max
10 18 0 9 3 18 11 25 18 33 25 45
18 24 0 10 5 20 13 28 20 36 28 48
24 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 97 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 91 147 135 200
180 200 2 30 25 71 63 117 107 163 150 230
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 45 125 110 210 195 300 275 410
355 400 3 70 55 145 130 240 225 340 315 460
400 450 3 80 60 170 150 270 250 380 350 510
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 20 130 110 260 240 400 380 570 540 760
710 800 20 140 120 290 270 450 430 630 600 840

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