A key that fits into a semicircular keyway cut in the shaft is woodruff key
The angle of I.S. thread (V-shaped) is 60 Degree
The reasons for rough and broken threads are
Thread cutting tool is blunt
The size of hole or diameter of the blank for bolt is not correct
The flutes of cutting tool are filled with chips
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.
A screw thread is formed on a cylindrical surface by cutting Helical grooves on its surface.