It begins at the bottom of the screw, and winds around and around the screw until it reaches the top, as is shown in [Fig. 60].
Fig. 60.
What is this inclined plane called?
It is called the thread of the screw.
How do the threads affect the screw?
When the threads are far apart, the inclined plane is steep; but it becomes less steep the nearer the threads are together.
When will the screw exert the most power?
The screw will exert the most power, when its threads are nearest together.
Of what use are screws, such as is shown in [Fig. 60]?