Boring is the operation of enlarging and truing a hole produced by drilling, punching, casting or forging. Boring cannot originate a hole. Boring is similar to the external turning operation and can be performed in a lathe. A single point cutting tool is entered into the material axially to perform the operations like chamfers, tapers, step turning etc. Boring operation is performed after the drilling. To enlarge the diameter of the hole boring is required.
Counter Boring is the operation of enlarging a hole through a certain distance from one end instead of enlarging the whole drilled surface. It is similar to a shoulder turning operation in external turning.
The principle of turning a taper hole is similar to the external taper turning operation and is accomplished by rotating the work on a chuck and feeding the tool at an angle to the axis of rotation of the work piece.