<P> A screw is a mechanism that converts rotational motion to linear motion , and a torque ( rotational force ) to a linear force . It is one of the six classical simple machines . The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside . The screw passes through a hole in another object or medium , with threads on the inside of the hole that mesh with the screw 's threads . When the shaft of the screw is rotated relative to the stationary threads , the screw moves along its axis relative to the medium surrounding it ; for example rotating a wood screw forces it into wood . In screw mechanisms , either the screw shaft can rotate through a threaded hole in a stationary object , or a threaded collar such as a nut can rotate around a stationary screw shaft . Geometrically , a screw can be viewed as a narrow inclined plane wrapped around a cylinder . </P>
<P> A screw is a mechanism that converts rotational motion to linear motion , and a torque ( rotational force ) to a linear force . It is one of the six classical simple machines . The most common form consists of a cylindrical shaft with helical grooves or ridges called threads around the outside . The screw passes through a hole in another object or medium , with threads on the inside of the hole that mesh with the screw 's threads . When the shaft of the screw is rotated relative to the stationary threads , the screw moves along its axis relative to the medium surrounding it ; for example rotating a wood screw forces it into wood . In screw mechanisms , either the screw shaft can rotate through a threaded hole in a stationary object , or a threaded collar such as a nut can rotate around a stationary screw shaft . Geometrically , a screw can be viewed as a narrow inclined plane wrapped around a cylinder . </P>
what is the spiral part of a screw called
what is the spiral part of a screw called
threads
threads