What is a thread?

Threads are classified according to the main functions they perform in a component.

Primary functions of a thread:    

• To form a mechanical coupling

• To transmit motion by converting a rotational movement into a linear movement, and yiceversa.

• To obtain a mechanical advantage, by using a small force tocreate a larger force.

Threads are also classified into various profiles or forms. The selection of these forms wilbe influenced by many other secondary, but still vital, functions.

Thread forms    

The thread profile defines the geometry of a thread and includes component diameters(major, pitch and minor), the thread profile angle, pitch and helix angle. The most commonthread forms or profiles produced today are shown below.