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The table below gives only the first-choice threads in the coarse and fine series. (The constant-pitch series includes threads up to 300mm diameter with pitches of 0.35, 0.5, 0.75, 1, 1.25, 1.5, 2, 3, 4 and 6mm.) The dimensions are in mm. The theoretical thread depths are approximately 0.613 and 0.541 of the pitch for external and internal threads respectively.

*These threads form part of the constant-pitch series.

Threads of diameter greater than 70mm in the coarse and fine series are taken from the constant-pitch series, with pitches of 6mm (coarse) or 4mm (fine) and first-choice diameters 72, 80, 90, 100, 110, 125, 140, 160, 180, 200, 220, 250, and 280mm.

The diameters are in inches; the two series are British Standard Whitworth (BSW) and British Standard Fine (BSF). Sizes which are not recommended are excluded here. The theoretical thread depth is approximately 0.640 of the pitch.

Dia.	Threads BSW	per in. BSF	Dia.	Threads BSW	per in BSF
3/16	24		2	4-1/2	7
1/4	20	26	2-1/4	4	6
5/16	18	22	2-1/2	4	6
3/8	16	20	2-3/4	3-1/2	6
7/16	14	18	3	3-1/2	5
1/2	12	16	3-1/4		5
9/16		16	3-1/2	3-1/4	4-1/2
5/8	11	14	3-3/4		4-1/2
3/4	10	12	4	3	4-1/2
7/8	9	11	4-1/4		4
1	8	10	4-1/2	2-7/8	4
1-1/8	7	9	5	2-3/4	4
1-1/4	7	9	5-1/2	2-5/8	4
1-1/2	6	8	6	2-1/2	4
1-3/4	5	7

The diameter are in inches. There is also an extra-fine series, and a constant-pitch series with threads up to 6in. diameter and pitches corresponding to 32, 28, 20, 16, 8, 6 and 4 threads per inch. The threads are identical in form to the I.S.O. metric threads.

The dimensions are in mm. No. 0 B.A. is not recommended and only even numbers are first-choice. The theoretical thread depth is 0.6 of pitch.