Small threads are mainly used in the industry of clocks, watches and instruments.

    Small thread standards in the world come from Switzerland: NIHS06-02 and NIHS0605.

The universal small thread standard is a metric thread standard which is unanimously recognized by all countries in the world and is expressed in M. The United States and the United Kingdom also use this standard. _

    Previously, standard S for small threads was combined with standard M for metric threads, which used the same tooth type and tolerance. At present, some countries still insist on using metric common thread code M to represent small threads. Later, it was found that such small threads were difficult to process and tapping/tapping often broke. In order to improve the machinability of small threads, it is decided to increase the flattening height of small diameter of internal threads so as to reduce the cutting depth of tap/tap (reduce cutting force) and increase the size of tap/tap diameter (increase tap/tap holding strength). At the same time, in order to ensure a certain contact height between the internal and external threads, the tolerance of the diameter of the external threads is tightened. The above changes in tooth shape and tolerance make the small thread different from the common thread made in metric system. From then on, the standard of small thread is separated from the common thread of metric system. Change the code of the small thread to S.

    In addition, the small thread codes in most countries and ISO are not quite the same. The small thread codes in most countries and ISO are S. Such as Switzerland, France, Japan, Britain and China. Small threads in a few countries are M, such as Germany and Russia, and small threads in the United States are coded UNM.

Shenzhen Comray Industry CO., Ltd.

2014-01-09