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STANDARD THREAD SIZES
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To download a PDF of the Standard Thread Sizes section (378 kb) please click on the PDF icon - >
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NPT - ANSI B2.1
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No of threads to inch
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1/8"
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10.2
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27
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4.5
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9.5
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1/4"
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13.5
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18
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5
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14.3
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3/8"
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17
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18
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6
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14.3
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1/2"
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21.2
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14
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6.1
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19.1
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3/4"
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26.5
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14
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8.6
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19.1
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1"
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33.2
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11 1/2
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10.1
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23.8
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1 1/4"
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41.9
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11 1/2
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10.6
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23.8
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1 1/2"
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48
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11 1/2
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10.6
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26.2
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No of threads to inch
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1/8"
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10.2
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27
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9.5
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1/4"
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13.5
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18
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14.3
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3/8"
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17
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18
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14.3
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1/2"
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21.2
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14
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19.1
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BSP TAPER B.S. 21-1985
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No of threads to inch
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1/8"
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5.10
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9.7
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28
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4
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9.5
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1/4"
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8.13
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13.1
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19
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6
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14.3
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3/8"
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12.17
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16.6
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19
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6.4
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14.3
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1/2"
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15.21
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20.9
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14
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8.2
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19.1
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3/4"
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21.27
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26.4
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14
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9.5
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19.1
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1"
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26.34
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33.2
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11
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10.4
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23.8
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1 1/4"
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33.42
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41.9
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11
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12.7
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23.8
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1 1/2"
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40.49
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47.8
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11
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12.7
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26.2
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2"
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59.60
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59.6
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11
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15.9
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27.0
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BSP PARALLEL B.S. 2779 - 1973
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No of threads to inch
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G
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1/8"
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5.10
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9.7
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28
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8
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1/4"
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8.13
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13.1
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19
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10
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3/8"
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12.17
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16.5
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19
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10
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1/2"
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15.21
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20.9
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14
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12
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3/4"
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21.17
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26.4
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14
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16
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1"
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26.34
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33.2
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11
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16
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1 1/4"
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33.42
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41.9
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11
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18
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1 1/2"
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40.49
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47.8
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11
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18
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2"
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50.60
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59.6
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11
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20
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No of threads to inch
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G
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1/8"
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5.10
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9.7
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28
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8
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1/4"
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8.13
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13.1
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19
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11
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3/8"
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12.17
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16.5
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19
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11.4
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1/2"
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15.21
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20.9
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14
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15
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3/4"
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21.17
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26.4
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14
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16.3
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1"
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26.34
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33.2
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11
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19.1
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1 1/4"
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33.42
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41.9
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11
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21.4
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1 1/2"
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40.49
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47.8
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11
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21.4
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ISO METRIC
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8 x 100
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8
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24 x 150
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14
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10 x 100
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8
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26 x 150
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16
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12 x 100
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8
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27 x 150
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16
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12 x 150
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10
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30 x 200
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16
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12 x 125
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8
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33 x 150
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16
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14 x 125
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10
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33 x 200
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16
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14 x 150
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10
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39 x 200
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18
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16 x 150
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10
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42 x 200
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18
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18 x 150
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12
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45 x 200
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18
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18 x 150
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12
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46 x 200
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18
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To download a PDF of the Standard Thread Sizes section (378 kb) please click on the PDF icon - >
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