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British Screw Thread Data
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Thread data with tapping and clearance drill sizes for the following commonly
used types.
* ME (Model Engineer) series.
* BA (British Association) series.
* BSP (British Standard Pipe) series.
* BSC (British Standard Cycle) series
* BSB (British Standard Brass) series.
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Model Engineer - ME
Size T.P.I. Tapping Drill Size.
mm Number/Letter/fraction
1/8 40 2.55 38
5/32 40 3.25 30
3/16 40 4.00 21
7/32 40 4.8 11
1/4 26 5.3 4
1/4 32 5.5 7/32
1/4 40 5.5 7/32
5/16 32 7.00 J
5/16 40 7.00 9/32
3/8 32 8.7 11/32
3/8 40 8.7 11/32
7/16 40 10.3 13/32
1/2 40 11.9 15/32
1/2 32 11.9 15/32
1/2 26 11.8
9/16 26 13.5 17.32
5/8 26 15.0 19/32
3/4 26 17.8 45/64
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British Association or BA series threads.
Size T.P.I. Tapping Drill Size (mm) Clearance Drill Size (mm)
0 25.40 5.2 6.1
1 28.22 4.5 5.4
2 31.35 4.1 4.8
3 34.79 3.5 4.2
4 38.48 3.0 3.7
5 43.05 2.65 3.3
6 47.92 2.3 2.85
7 52.91 2.1 2.55
8 59.07 1.8 2.3
9 65.12 1.6 1.95
10 72.57 1.4 1.75
11 81.93 1.2 1.5
12 90.71 1.05 1.3
13 101.60 .975 1.15
14 110.43 .80 1.00
15 120.95 .70 .90
16 133.68 .60 .80
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British Standard Pipe or BSP series
Size T.P.I. Tapping Drill Size
mm letter/fraction
1/8 28 8.7 11/32
1/4 19 11.9 15/32
3/8 19 15.0 19/32
1/2 14 19.0 3/4
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British Standard Cycle or BSC series
Size T.P.I. Tapping Drill Size
mm letter/fraction
5/16 26 7.00 J
3/8 26 8.75 11/32
7/16 26 10.25
1/2 26 11.90 15/32
5/8 26 15.00 19/32
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British Standard Brass or BSB series
Size T.P.I. Tapping Drill Size
mm letter/fraction
5/16 26 6.90 I
3/8 26 8.40 Q
7/16 26 9.92 25/64
1/2 26 11.50 29.64
5/8 26 14.50 37/64
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