What are the different types of screw thread?

Answer 1

A thread may be either right-hand or left-hand. A right-hand thread on an external member advances into an internal thread when turned clockwise; a left-hand thread advances when turned counterclockwise. If a single helical groove is cut or formed on a cylinder, it is called a single-thread screw. Should the helix angle be increased sufficiently for a second thread to be cut between the grooves of the first thread, a double thread will be formed on the screw. Double, triple, and even quadruple threads are used whenever a rapid advance is desired, as on valves.

Pitch and major diameter designate a thread. Lead is the distance advanced parallel to the axis when the screw is turned one revolution. For a single thread, lead is equal to the pitch; for a double thread, lead is twice the pitch. For a straight thread, the pitch diameter is the diameter of an imaginary coaxial cylinder that would cut the thread forms at a height where the width of the thread and groove would be equal.

Thread forms have been developed to satisfy particular requirements. Where strength is required for the transmission of power and motion, a thread having faces that are more nearly perpendicular to the axis is preferred. These threads, with their strong thread sections, transmit power nearly parallel to the axis of the screw. (Sci-Tech Encyclopedia)

For the source and more detailed information concerning your request, click on the related links section (Answers.com) indicated directly below this answer section.

Answer 2

a srew is a type of simple machine