Thread Data & Tapping Drill Size Comparison

Metric Coarse

Nom. Dia (mm) Pitch (mm) Tapping Drill (mm)
2.00.401.60
2.20.451.75
2.50.452.05
3.00.502.50
3.50.602.90
4.00.703.30
4.50.753.70
5.00.804.20
6.01.005.00
7.01.006.00
8.01.256.80
9.01.257.80
10.01.508.50
11.01.509.50
12.01.7510.20
14.02.0012.00
16.02.0014.00
18.02.5015.50
20.02.5017.50
22.02.5019.50
24.03.0021.00
27.03.0024.00
30.03.5026.50
33.03.5029.50
36.04.0032.00
39.04.0035.00
42.04.5037.50
45.04.5040.50
48.05.0043.00
52.05.0047.00
56.05.5050.50
60.05.5054.50

Metric Fine

Nom. Dia (mm) Pitch (mm) Tapping Drill (mm)
2.00.251.75
2.20.251.95
2.50.352.15
3.00.352.65
3.50.353.15
4.00.503.50
4.50.504.00
5.00.504.50
6.00.755.20
7.00.756.20
8.01.007.00
10.00.759.20
10.01.009.00
10.01.258.80
12.01.0011.00
12.01.2510.80
12.01.5010.50
14.01.2512.80
14.01.5012.50
16.01.0015.00
16.01.5014.50
18.01.5016.50
20.01.0019.00
20.01.5018.50
20.02.0018.00
22.01.5020.50
24.02.0022.00
25.01.5023.50
27.02.0025.00
30.02.0028.00
32.01.5030.50
33.02.0031.00
36.003.0033.00
39.003.0036.00
Table Key
Spark Plug
Metric Conduit

Unified Coarse

Size Nom. Dia (Inch) Pitch (T.P.I) Tapping Drill (mm)
No.10.073641.55
No.20.086561.85
No.30.099482.10
No.40.112402.35
No.50.125402.65
No.60.138322.85
No.80.164323.50
No.100.190243.90
No.120.216244.50
1/4205.10
5/16186.60
3/8168.00
7/16149.40
1/21310.80
9/161212.20
5/81113.50
3/41016.50
7/8919.50
1822.25
1.1/8725.00
1.1/4728.00
1.3/8630.75
1.1/2634.00
1.3/4539.50
24.545.00

Unified Fine

Size Nom. Dia (Inch) Pitch (T.P.I) Tapping Drill (mm)
No.00.060801.25
No.10.073721.55
No.20.086641.90
No.30.099562.15
No.40.112482.40
No.50.125442.70
No.60.138402.95
No.80.164363.50
No.100.190324.10
No.120.216284.70
1/4285.50
5/16246.90
3/8248.50
7/16209.90
1/22011.50
9/161812.90
5/81814.50
3/41617.50
7/81420.40
11223.25
1.1/81226.50
1.1/41229.50
1.3/81232.75
1.1/21236.00

British Standard Whitworth

Nom. Dia (Inch) Pitch (T.P.I) Tapping Drill (mm)
1/8402.55
3/16243.70
1/4205.10
5/16186.50
3/8167.90
7/16149.30
1/21210.50
9/161212.10
5/81113.50
11/161115.00
3/41016.25
7/8919.25
1822.00
1.1/8724.75
1.1/4728.00
1.1/2633.50
1.3/4539.00
24.1/244.50
2.1/4451.00
2.1/2457.00
2.3/43.1/262.00
33.1/269.00

British Standard Fine

Nom. Dia (Inch) Pitch (T.P.I) Tapping Drill (mm)
3/16323.70
7/3228
1/4265.10
9/32266.50
5/16226.50
3/8207.90
7/16189.30
1/21610.50
9/161612.10
5/81413.50
11/161415.00
3/41216.25
7/81119.25
11022.00
1.1/8924.75
1.1/4928.00
1.3/8833.50
1.1/2833.50
1.5/8839.00
1.3/4739.00
2744.50
2.1/4651.00
2.1/2657.00
2.3/4662.00
3569.00

British Standard Pipe

Nom. Dia (Inch) Pitch (T.P.I) Tapping Drill (mm)
1/8288.80
1.41911.80
3/81915.25
1/81419.00
5/81421.00
3/41424.50
7/81428.25
11130.75
1.1/41139.50
1.1/21145.00
1.3/41151.00
21157.00

British Association

Size Pitch (mm) Tapping Drill (mm)
No.01.005.10
No.10.904.50
No.20.814.00
No.30.733.40
No.40.663.00
No.50.592.65
No.60.532.30
No.70.482.05
No.80.431.80
No.90.391.55
No.100.351.40
No.110.311.20
No.120.281.05
No.130.250.98
No.140.230.8