All of the above
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
Pitch of thread
The distance between one point on a screw thread and the corresponding point on the next thread, measured parallel to the axis is called as Pitch of Thread.
Lead and pitch are equal
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.
Acme thread
The American Acme form has an included flank angle of 29-degrees. The metric Trapezoidal thread is at 30-degrees.
Screw thread micrometer
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.
