Page 11 - SIMPLE MACHINES

4. SCREW –

 A screw is another simple machine, which is an inclined plane
wrapped around a cylinder. The inclined plane forms ridges in a
spiral along the cylinder. These ridges are called the threads of
the screw. The distance between the threads is called "the pitch"
of the screw.
 Screw is inserted into a piece of wood using a screwdriver. It is
difficult to pull out a screw out of a piece of wood compared to a
nail. This is because a screw is really an inclined plane that goes
round and round. Thus, it holds things together, through a longer

distance with a stronger grip.
 We use screws to do many jobs. Bolts are used to put together many small parts of
complex machines, revolving stools, bases of most light bulbs. Even your pen caps have
screws.