The designation of the screw threads is in a close connection with the system of measurement including the fact that this system
influences the definition of the screw thread. In the U.S.A., it is a very special situation because they used both American customary
system and metric system. This situation led to an original way of screw thread designation which combines experiences acquired for
both systems and generalizes them. The paper presents the principles used for designations of American screw threads, starting from
the general principles, and illustrates them by examples. In the same time, in the paper are done observations about some mismatch
in the standards connected whit the designation of screw thread and proposals to eliminate them and for designations of some screw
thread.
Screw thread, Screw thread designation, American system, Metric system