How to express the pitch for the different thread types?

Often people are confused on how exactly to express a certain thread size.
The most mistakes are made when people have to work with a different measurement system then they are used to.
The imperial and metric thread systems use a different way of indicating the pitch, except for the imperial thread type BA, for which the pitch is indicated as the metric thread system.

For the metric  and imperial BA thread system, the pitch is a single thread measured and expressed in millimetres.
For example M10x1,5. The number 1,5 means that the distance between a point on 2 adjecent threads measures 1,5 mm.

For the imperial thread systems, UNF-UNC-BSF-BSW, the pitch is expressed in numbers of threads per inch or tpi.
For example 1/4-20. The number 20 means that there are 20 threads per inch or 20TPI.

To find out more about UNF-UNC-BSF-BSW please visit link