The British Standard Whitworth (BSW) thread system is commonly used in the United Kingdom for various applications. It features a 55-degree thread angle and rounded peaks and valleys. The thread data chart below provides common thread sizes and their corresponding thread pitch, major diameter, minor diameter, pitch diameter, and tapping drill size.

SIZETPIEXTERNALINTERNALDRILL SIZEDRILL SIZE
BSW 55 MAJORSMINORSCLEARANCE HOLETAPPED HOLE
  INCHMMINCHMMINCHMMINCHMM
1/16600.06201.590.04101.05 1.99 1.15
3/32480.09402.380.06701.70 2.67 1.90
1/8400.12503.180.09302.369/643.57# 382.60
5/32320.15603.970.11602.9511/644.371/83.20
3/16240.18704.750.13403.4013/645.16# 273.70
7/32240.21905.600.16604.2215/645.95# 194.30
1/4200.25006.350.18604.7217/646.75# 95.00
5/16180.31207.920.24106.1221/648.331/46.40
3/8160.37509.530.29507.4925/649.925/168.00
7/16140.437011.100.34608.7929/6411.51U9.40
1/2120.500012.700.39309.9817/3213.4927/6410.80
9/16120.563014.290.456011.5819/3215.0815/3212.00
5/8110.625015.880.509012.9321/3216.6717/3213.50
11/16110.688017.480.571014.50 17.75 15.00
3/4100.750019.050.622015.8025/3219.8421/3217.00
13/16100.813020.650.684017.37 21.00 18.00
7/890.875022.230.733018.6229/3223.0249/6419.50
15/1690.938023.830.795020.19 24.00 20.75
181.000025.400.840021.341 1/1626.997/822.50
1 1/871.125028.580.942023.931 3/1630.16125.50
1 1/471.250031.751.067027.101 5/1633.341 7/1628.50
1 3/861.375034.931.162029.511 7/1636.511 7/3231.00
1 1/261.500038.101.287032.691 9/1639.691 11/3234.50
1 5/851.625041.281.369034.77 41.50 35.50
1 3/451.750044.451.494037.95 45.00 38.50
1 7/84.51.875047.631.591040.40 48.00 41.25
24.52.000050.801.715043.57 51.00 44.50
2 1/44       50.00
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