Friction you all know is nothing but just a force When a body moves or tends to move on another body, the force, which appears between the surfaces in contact and resists the motion or tendency towards motion, of one body relative to the other is defined as friction or frictional force or force of friction.
Types of Friction
It is the friction, experienced by a body when at rest.
It is the friction experienced by a body, when in motion. The dynamic friction is also called kinetic friction and is less than the static friction.
a. Sliding friction
b. Rolling friction
c. Pivot friction
The screws bolts, studs, nuts etc are widely used in various machines and structures for temporary fastenings have screw threads, which are made by cutting a continuous helical groove on a cylindrical surface.
p = Pitch of the screw,
d= mean diameter of the screw and
n= Number of threads in one lead.