1. Screw Threads, BSW,
The British Standard Whitworth series was the result, in 1841, of the efforts made by Sir Joseph Whitworth to get accepted some form of standardisation of screw threads. The thread is a vee form. The angle is 55 degrees and it is rounded at the root and the crest. The B.S.W. series is used in all branches of engineering

2. British Standard Fine
The British Standard Fine series was introduced by the Engineering Standards Committee, in 1908 to supplement the Whitworth series in cases where finer pitches were required. The thread is the same as the Whitworth Standard
Sir Joseph Whitworth

3. British Standard Pipe Series
The British Standard pipe series is the standard used when threading pipes for gas, water or steam. The thread form is the same as the Whitworth Standard. The nominal size refers to the bore of the pipe

4. BSP threads continued
If you were to look at tables for BSP it will be seen that this series is finer than the others, allowing for greater locking power and also preventing excessive weakening of the pipe wall

5. British Association Series (BA)
The British Association series is recommended for use below ¼ in (6.35mm) dia. The vee thread has an angle of 47 ½ degrees and is rounded top and bottom.

6. The Unified series
The Unified series (U.N. fine and U.N. coarse) were introduced to obtain some standardisation between Great Britain, the U.S.A. and Canada. They are a compromise between the American National Series and British Whitworth series
In November 1948 the Unified thread was agreed upon by the UK, the US and Canada to be used as the single standard for all countries using inch units. In 1965 the British Standards Institution issued a policy statement requesting that organisations should regard the BSW, BSF and BA threads as obsolescent. The first choice replacement for future designs was to be the ISO metric thread with the ISO inch (Unified) thread being the second choice.

7. ISO Metric Threads
Most threads in general use throughout Britain and western Europe now conform to the ISO metric standards. ISO is an abbreviation for International Standards Organisation.
The thread angle on all ISO metric threads is 60 degrees.