Base circle is the smallest circle that can be drawn to the cam profile.

In radial cams, the follower reciprocates or oscillates in a direction perpendicular to the cam axis.

It is the angle between the direction of the follower motion and a normal to the pitch curve. This angle is very important in designing a cam profile. If the pressure angle is too large, a reciprocating follower will jam in its bearings.

Since with high speed engines, maximum acceleration is required and that is possible only through cycloidal motion.

When the contacting end of the follower is a roller, it is called a roller follower. Since the rolling motion takes place between the contacting surfaces (i.e. the roller and the cam), therefore the rate of wear is greatly reduced. In roller followers also the side thrust exists between the follower and the guide. The roller followers are extensively used where more space is available such as in stationary gas and oil engines and aircraft engines.

Base circle is the smallest circle that can be drawn to the cam profile.

When the motion of the follower is along an axis passing through the centre of the cam, it is known as radial follower.

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When the contacting end of the follower is of spherical shape, it is called a spherical faced follower. It may be noted that when a flat-faced follower is used in automobile engines, high surface stresses are produced. In order to minimise these stresses, the flat end of the follower is machined to a spherical shape.

When the motion of the follower is along an axis away from the axis of the cam centre, it is called off-set follower.