………..Continued - Parts of Radial Drilling Machine -Functions - Classifications Drilling Machine – Operations

Unit 4 Machine Tools Machine Tools (Basic Elements, Working principle and Types of Operations) Lathe Machine – Centre Lathe Drilling Machine – Radial Drilling Machine Grinding Machine -Surface grinding, cylindrical grinding, centerless grinding, All operations

Operations performed on the Drilling Machine – 1. DRILLING OPERATION: In this process, a cylindrical hole is produced by removing metal by the rotating edges of a cutting tool called as drill. Before drilling the centre of the hole is located on the work piece. Then the centre punch is used to produce an indentation at the centre. The drill point is pressed at this centre point to produce the required hole. 2. REAMING OPERATION – It is an operation of sizing and finishing a hole which has been previously drilled. In order to finish a hole and to bring it to the accurate size, the hole is drilled slightly undersize. The speed of the spindle is made half that of drilling and automatic feed may be employed. The tool used for reaming is known as reamer which has multiple cutting edges. Reamer cannot originate a hole. It simply follows the path which has been previously drilled and removes a very small amount of metal.

Operations performed on the Drilling Machine – 3. BORING OPERATION: This operation is used for enlarging a hole to bring it to the required size and have a better finish. This operation is also used to machine the internal surface of a hole which is already produced in casting. 4. COUNTER BORING OPERATION: It is the operation of enlarging the end of a hole cylindrically. The enlarged hole forms a square shoulder with the original hole. This is necessary in some cases to accommodate the heads of bolts, studs and pins. 5. COUNTERSINKING OPERATION: It is the operation of making a cone shaped enlargement of the end of a hole to providea recess for a flat head screw or countersunk rivet fitted into the hole. The tool used for is called as countersink. Standard countersinks have 60o, 82o included angle.

Operations performed on the Drilling Machine – 6. TAPPING OPERATION: It is the operation of cutting internal threads in already produced hole by means of cutting tool called as a tap. 7. GRINDING OPERATION: This operation is performed to finish hardened hole by a revolving grinding wheel fitted on a spindle and fed up and down.

Operations performed on the Drilling Machine –

Trepanning hole by removing metal along the Cutting Edges Guide WP Trepanning is the operation of producing a hole by removing metal along the circumference of a hollow cutting tool Trepanning is performed for producing large holes which can not be produced by any drilling operations

DRILLING

Reaming Reaming