NTN - Large Bearings

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Bearing Internal Clearance 5. Bearing Internal Clearance 5.1 Bearing internal clearance Bearing internal clearance (initial clearance) is the amount of internal clearance a bearing has before being installed on a shaft or in a housing. As shown in Fig. 5.1, when either the inner ring or the outer ring is fixed and the other ring is free to move, displacement can take place in either an axial or radial direction. This amount of displacement (radially or axially) is termed the internal clearance and, depending on the direction, is called the radial internal clearance or the axial internal clearance. When the internal clearance of a bearing is measured, a slight measurement load is applied to the raceway so the internal clearance may be measured accurately. However, at this time, a slight amount of elastic deformation of the bearing occurs under the measurement load, and the clearance measurement value (measured clearance) is slightly larger than the true clearance. This discrepancy between the true bearing clearance and the increased amount due to the elastic deformation must be compensated for. These compensation values are given in Table 5.1. For roller bearings the amount of elastic deformation can be ignored. The internal clearance values for each bearing class are shown in Tables 5.2 through 5.9. 5.2 Internal clearance selection The internal clearance of a bearing under operating conditions (effective clearance) is usually smaller than the same bearing's initial clearance before being installed and operated. This is due to several factors including bearing fit, the difference in temperature between the inner and outer rings, etc. As a bearing's operating clearance has an effect on bearing life, heat generation, vibration, noise, etc.; care must be taken in selecting the most suitable operating clearance. Effective internal clearance: The internal clearance differential between the initial clearance and the operating (effective) clearance (the amount of clearance reduction caused by interference fits, or clearance variation due to the temperature difference between the inner and outer rings) can be calculated by the following formula: where, eff o f t 5.1 eff : Effective internal clearance, mm o : Bearing internal clearance, mm f : Reduced amount of clearance due to interference, mm t : Reduced amount of clearance due to temperature differential of inner and outer r, mm δ2 Table 5.1 Examples of applications where bearing clearances other than normal clearance are used δ δ1 Operating conditions Applications Selected clearance With heavy or shock Railway vehicle axles C3 load, clearance is great. Vibration screens C3C4 With direction indeterminate load, both inner and outer rings are tight-fitted. Shaft or inner ring is heated. To reduce shaft runout, clearance is adjusted. Railway vehicle traction motors Tractors and final speed regulators Paper making machines and driers Rolling mill table rollers Main spindles of lathes (Double-row cylindrical roller bearings) C4 C4 C3C4 C3 C9NA C0NA Radial clearance = Axial clearance =12 Fig. 5.1 Internal clearance A-29
Bearing Internal Clearance (1) Reduced clearance due to interference When bearings are installed with interference fits on shafts and in housings, the inner ring will expand and the outer ring will contract; thus reducing the bearings' internal clearance. The amount of expansion or contraction varies depending on the shape of the bearing, the shape of the shaft or housing, dimensions of the respective parts, and the type of materials used. The differential can range from approximately 70% to 90% of the effective interference. f (0.700.90) ∆deff (5.2) where, f : Reduced amount of clearance due to interference, mm ∆deff : Effective interference, mm (2) Reduced internal clearance due to inner/outer ring temperature difference. During operation, normally the outer ring will range from 5 to 10 cooler than the inner ring or rotating parts. However, if the cooling effect of the housing is large, the shaft is connected to a heat source, or a heated substance is conducted through the hollow shaft; the temperature difference between the two rings can be even greater. The amount of internal clearance is thus further reduced by the differential expansion of the two rings. t ∆TDo (5.3) where, t : Amount of reduced clearance due to heat differential, mm : Bearing steel linear expansion coefficient 12.5 10 -6 /˚C ∆T : Inner/outer ring temperature differential, Do : Outer ring raceway diameter, mm Outer ring raceway diameter, Do, values can be approximated by using formula (5.4) or (5.5). For ball bearings and self-aligning roller bearings, Do 0.20 (d 4.0D) (5.4) For roller bearings (except self-aligning), Do 0.25 (d 3.0D) (5.5) where, d : Bearing bore diameter, mm D : Bearing outside diameter, mm Table 5.2 Radial internal clearance of deep groove ball bearings Unit m Nominal bore diameter C2 Normal C3 C4 C5 dmm over incl. min max min max min max min max min max 80 100 120 100 120 140 1 2 2 18 20 23 12 15 18 36 41 48 30 36 41 58 66 81 53 61 71 84 97 114 75 90 105 120 140 160 140 160 180 160 180 200 2 2 2 23 25 30 18 20 25 53 61 71 46 53 63 91 102 117 81 91 107 130 147 163 120 135 150 180 200 230 200 225 250 225 250 280 2 2 2 35 40 45 25 30 35 85 95 105 75 85 90 140 160 170 125 145 155 195 225 245 175 205 225 265 300 340 280 315 355 315 355 400 2 3 3 55 60 70 40 45 55 115 125 145 100 110 130 190 210 240 175 195 225 270 300 340 245 275 315 370 410 460 400 450 500 450 500 560 3 3 10 80 90 100 60 70 80 170 190 210 150 170 190 270 300 330 250 280 310 380 420 470 350 390 440 510 570 630 560 630 710 630 710 800 10 20 20 110 130 140 90 110 120 230 260 290 210 240 270 360 400 450 340 380 430 520 570 630 490 540 600 690 760 840 800 900 1,000 1,120 900 1,000 1,120 1,250 20 20 20 20 160 170 180 190 140 150 160 170 320 350 380 410 300 330 360 390 500 550 600 650 480 530 580 630 700 770 850 920 670 740 820 890 940 1,040 1,150 1,260 A-30
Page 1 and 2: For New Technology Network R corpor
Page 3 and 4: Warranty NTN warrants, to the origi
Page 5 and 6: A-2
Page 7 and 8: A-4
Page 9 and 10: Load Rating and Life n min -1 60,00
Page 11 and 12: Bearing Load Calculation 2. Bearing
Page 13 and 14: A-10A-30
Page 15 and 16: Bearing Tolerances Table 3.3 Tolera
Page 23 and 24: Bearing Tolerances 3.2 Limits and t
Page 25 and 26: Bearing Fits 4. Bearing Fits 4.1 In
Page 27 and 28: Bearing Fits (3) Consideration must
Page 29 and 30: Bearing Fits Table 4.3 Standard fit
Page 31: Bearing Fits Table 4.6 Fits for inc
Page 35 and 36: Bearing Internal Clearance Table 5.
Page 41 and 42: Lubrication 6. Lubrication 6.1 Lubr
Page 43 and 44: Lubrication 6.3.2 Base oil Natural
Page 45 and 46: Lubrication 6.5 Oil lubrication Oil
Page 47 and 48: Lubrication Table 6.9 Factor K Expe
Page 49 and 50: MEMO A-46
Page 51 and 52: INDEX OF BEARING TABLES Deep Groove
Page 53 and 54: Deep Groove Ball Bearings
Page 55 and 56: Deep Groove Ball Bearings D r B r d
Page 61 and 62: Deep Groove Ball Bearings r D B r d
Page 63 and 64: Angular Contact Ball Bearings
Page 65 and 66: Angular Contact Ball Bearings 1. 2
Page 67 and 68: Angular Contact Ball Bearings Singl
Page 81 and 82: Double Row Angular Contact Ball Bea
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Double Row Angular Contact Ball Bea
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Cylindrical Roller Bearings
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Cylindrical Roller Bearings Table 3
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Single Row Cylindrical Roller Beari
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Multi-Row Cylindrical Roller Bearin
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4-Row Cylindrical Roller Bearings C
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SL Type Cylindrical Roller Bearings
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Tapered Roller bearings
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Tapered Roller Bearings Table 2 Str
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Tapered Roller Bearings Inch system
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Tapered Roller Bearings Inch system
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Single Row Tapered Roller Bearings
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Double Row Tapered Roller Bearings
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Double Row Steep Slope Tapered Roll
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Four Row Tapered Roller Bearings C2
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Sealed Four Row Tapered Roller Bear
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Spherical Roller bearings
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Spherical Roller Bearings 2. Dimens
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Spherical Roller Bearings B r r D d
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Thrust bearings
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Thrust Bearings 1. 3 Tapered roller
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Thrust Bearings d1 d D1 D r r T da
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Thrust Bearings d1 d D1 D r r T da
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Thrust Roller Bearings r d1 d D D1
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Thrust Roller Bearings r d1 d T r D
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Thrust Roller Bearings r d1 d T r D
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Tapered Roller Thrust Bearings (Sin
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Tapered Roller Thrust Bearings (Sin
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Tapered Roller Thrust Bearings (Dou
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Self-Aligning Thrust Roller Bearing
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Bearings for special applications C
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Split Cylindrical Roller Bearings:
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Double-Fractured Split Cylindrical
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Bearings for Preparing Rolls: Sendz
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Enclosed-Type Tapered Roller Bearin
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Tapered Roller Thrust Bearings: Scr
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Tapered Roller Thrust Bearings: Scr
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Tension Leveler Roll Unit: Cartridg
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Turn Table Bearings: 3-Row Cylindri
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Sealed Spherical Roller Bearings: M
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Spherical Surface Slide Bearings ¡
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Catalog List & Appendix Table
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Catalog List CATALOG TITLES CATALOG
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Appendix Table D-5 Appendix table 1
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Appendix Table Appendix table 2: Co
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Appendix Table h4 h5 h6 h7 h8 h9 h1
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Appendix Table H7 H8 H9 H10 H11 H13
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Appendix Table Appendix table 8: Vi
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D-15 1/64 1/32 3/64 1/16 5/64 3/32
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NTN - Large Bearings

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