8 February 2017

Drilling machine operation

The operation of drilling consists of producing a hole in an object by forcing a rotating drill against it. A hole in an object by forcing a rotating drill against it.


Drilling machine has done various operation following below :
  1. Drilling 
  2. Reaming
  3. Boring
  4. Counter boring
  5. Countersinking
  6. Spot facing
  7. Tapping
  8. Trepanning
  • Drilling :
Drilling is an operation of producing a circular hole in solid metal by rotating the drill and feeding it through the job.
Before starting the drilling it is necessary to mark the position of the hole on the workpiece.


  • Reaming :
Reaming is an operation of sizing and shaping a hole using a tool called reamer.
Reamer is a multitoothed tool designed for a remove relatively small amount of material from a previously drilling hole.
Initially, the hole is drilled slightly smaller in size.

  • Boring :
Boring of a process of aligning, sizing and finishing a cylindrical hole.
In boring single point cutting tool which rotates relative to the stationary workpiece.
Boring is often used to enlarge the drilling holes.


  • Counter boring :
Counter boring is the operation of enlarging one of an existing hole concentric with the original hole with a square bottom.
A counter tool is known as counterbore it has a pilot.
The pilot enters the previously drilled holes and aligns the tool so that the counterbored hole is concentric with the existing one.

Counter boring

  • Countersinking :
Countersinking is performed after the drilling to provide a space for the head of the fastener, such as a screw, to sit flush with the workpiece surface.
A countersink tool enlarges the top portion of an existing hole to a cone-shaped opening.
Common included angle for a countersink tool is 60 82 90 100 118 200 degrees.  


  • Spot facing :
Spot facing is the process of producing a flat machined surface generally around a hole perpendicular to the hole axis.
The flat surface allows the bottom of a screw or bolt to seat squarely with the material.
Spot facing is commonly done on castings where the irregular surface is found.

Spot facing
  • Tapping :
Tapping is a thread cutting for producing internal thread.
Tapping uses multi-point cutting tool called taps may be done manually or on drilling machine.

  • Trepanning :
Trepanning is the process for making large holes in sheet metal.
A small diameter hole is drilled in center for drilling large diameter hole.
Holes up to diameter of 350 mm can be cut by this operation.