What is an involute curve ?
As shown in the figure below, the curve traced by the end of the thread (the pencil) as the thread is unwound from a cylinder while the thread is in tension, is called an involute curve.
In this instance, the circle of the cylinder on which the thread is wound is called the base circle.
Presently, almost all gears in use utilize the involute tooth form by using a part of this involute curve.
The involute tooth form is made up by using a part of this involute curve (near the cylinder).
