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Standard USA Bolt Shank Dimensions (All dimensions in units of mm unless otherwise specified.)
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Unified
Bolt Threads
Coarse (UNC)
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Unified
Bolt Threads
Fine (UNF)
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USA Size
Desig- nation
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Nominal
(Major) Diam- eter,
Dn
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Threads
per
inch,
n
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Pitch (mm
per thread), p
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Tensile
Stress Dia- meter,
Dt
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Shear
Stress Minor Dia- meter,
Ds
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Threads
per
inch,
n
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Pitch
(mm per thread),
p
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Tensile
Stress Dia- meter,
Dt
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Shear
Stress Minor Dia- meter,
Ds
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0
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1.524
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80
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0.3175
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1.215
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1.112
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1
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1.854
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64
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0.3969
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1.468
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1.339
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72
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0.3528
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1.510
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1.396
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2
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2.184
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56
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0.4536
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1.742
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1.595
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64
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0.3969
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1.798
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1.669
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3
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2.515
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48
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0.5292
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1.999
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1.827
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56
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0.4536
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2.073
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1.925
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4
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2.845
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40
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0.6350
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2.226
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2.020
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48
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0.5292
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2.329
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2.157
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6
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3.505
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32
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0.7938
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2.732
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2.474
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40
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0.6350
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2.887
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2.680
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8
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4.166
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32
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0.7938
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3.392
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3.134
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36
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0.7056
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3.478
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3.249
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10
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4.826
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24
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1.0583
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3.795
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3.451
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32
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0.7938
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4.053
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3.795
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12
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5.486
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24
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1.0583
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4.455
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4.112
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28
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0.9071
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4.603
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4.308
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0.2500
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6.350
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20
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1.2700
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5.113
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4.700
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28
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0.9071
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5.466
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5.172
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0.3125
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7.938
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18
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1.4111
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6.563
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6.104
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24
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1.0583
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6.906
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6.563
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0.3750
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9.525
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16
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1.5875
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7.978
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7.463
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24
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1.0583
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8.494
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8.150
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0.4375
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11.112
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14
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1.8143
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9.345
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8.756
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20
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1.2700
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9.875
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9.463
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0.5000
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12.700
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13
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1.9538
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10.796
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10.162
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20
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1.2700
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11.463
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11.050
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0.5625
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14.288
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12
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2.1167
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12.225
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11.538
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18
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1.4111
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12.913
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12.454
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0.6250
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15.875
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11
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2.3091
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13.625
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12.875
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18
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1.4111
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14.500
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14.042
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0.7500
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19.050
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10
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2.5400
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16.575
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15.750
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16
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1.5875
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17.503
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16.988
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0.8750
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22.225
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9
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2.8222
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19.475
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18.559
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14
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1.8143
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20.457
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19.868
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1.0000
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25.400
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8
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3.1750
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22.307
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21.276
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12
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2.1167
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23.338
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22.650
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1.1250
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28.575
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7
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3.6286
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25.040
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23.861
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12
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2.1167
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26.513
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25.825
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1.2500
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31.750
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7
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3.6286
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28.215
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27.036
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12
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2.1167
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29.688
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29.000
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1.3750
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34.925
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6
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4.2333
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30.801
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29.426
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12
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2.1167
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32.863
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32.175
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1.5000
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38.100
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6
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4.2333
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33.976
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32.601
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12
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2.1167
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36.038
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35.350
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Pitch
p is longitudinal length per thread. Note that p = 1 /
n, where n = threads per unit length.
For USA bolts, tensile stress diameter, by definition, is Dt = Dn
– 0.974279 p.
For USA bolts, minor (shear) diameter, by definition, is Ds = Dn
– 1.299038 p.
For metric bolts, tensile stress diameter, by definition, is Dt = Dn
– 0.938194 p.
For metric bolts, minor (shear) diameter, by definition, is Ds = Dn
– 1.226869 p.
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