Lead is the distance of a threaded component moves along the matching component during one complete revolution. For a single start thread the lead is equal to the pitch.
The American Acme form has an included flank angle of 29-degrees. The metric Trapezoidal thread is at 30-degrees.
Screw thread micrometer is used to measure the effective diameter of the screw threads. This dimension is important, because the area of the thread flanks in the vicinity of the pitch line is where the greatest transmission of force occurs between mating threads.
A screw thread is formed on a cylindrical surface by cutting Helical grooves on its surface.
The root of ISO metric thread is Round