Drilling Machine Operations | Functions of a Drilling Machine



           Drilling is the operation of cutting a round hole by a rotating tool called drill. Before the process of drilling, the center of the hole is positioned on the work piece. Two lines at right angles to each other are drawn. A center punch is used to mark the center point at the meeting of two lines. The rotating drill is pressed at the center point scribed on the work piece to produce the hole.

01 - process of drilling - DRILLING OPERATIONS

        Drilling does not produce a precise hole. Only rough internal surface will be produced by the drilling process. The hole is lightly bigger than the size of the drill bit used due to the vibration of the drill.


01 - process of reaming - reaming operation

           the process of sizing and finishing the already drilled hole is called as Reaming. The tool used for reaming is known as a reamer. It is a cylindrical tool having many cutting edges. Reamer cannot drill a hole. It simply follows the path of an previously drilled hole. It removes a very small volume of metal. The volume of metal removed in reaming is approximately 0.375mm. In this process the spindle speed is half that of drilling process.


01 - process of boring - boring operation.

       Boring is a process of increasing a hole with the help of a single point cutting tool. Boring is done where right size drill is not available. If the size of the hole is very large the hole cannot be drilled. Then to enlarge the hole boring is done. By boring, the hole is finished accurately to the required size. The internal surface of a hole in a casting is machined by this boring process. The cutter is held in a boring bar which has a tapped shank to fit into spindle hole.

          The operation of enlarging the end of a hole cylindrically is known as a counter boring. The operation of making a cone-shaped enlargement of the end of a hole is known as countersinking.

Spot Facing

          The operation of squaring and smoothing the surface around hole is known as spot facing. Figure illustrates the process of spot facing.


         The operation of cutting internal threads in a hole by using a cutting tool is called as tapping. A tap has cutting edges in the shape of threads. the tap is screwed into the hole which will remove metal and cut internal threads.

01 - process of tapping - tapping operation

           Tap drill size = 0.8 x Outside diameter of the thread.


         The operation of manufacturing a large hole by removing metal along the circumference of a hollow cutting tool is known as trepanning. There is a pilot inside the trepanning tool which pass in the small previously drilled hole to produce the larger. It is used for the diameter more than size of particular machine and where hole depth is much more in comparison with normal work.


          The operation of increasing the dimension of thehole at any point between its ends is known as undercutting.


           The operation of removing large amount of stock with respect to lapping and honing operations from hardened material and super finishing a surface accuracy upto ±0.0025mm by means of a grinding tool wheel is known as grinding.


          The operation of sizing hardened holes and extremely limited in stock removal is known as lapping.

01 - process of lapping - lapping operation


       The operation of finishing large holes such as automobile cylinders by means of slow moving abrasives is known as honing.

01 - process of hoining - hoining operation

Application of Laser in Mechanical Engineering | Laser Heat Treatment Process | Laser Metal Cutting and Joining Process

      Process involving heating and cooling under the controlled conditions of a material to obtain certain desirable properties is known as heat treatment.

1. Laser surface alloying

       The different types of heat treatment process using laser are shown in the picture. In the process of annealing there is no zone affected by the heat and melting takes place only in the level of picometer thickness.

        In hardening process there is a zone in the form of hemisphere which is affected by the heat. In this surface alloying method there is a coating of alloying or cladding materials deposited on the substrate surface.

01 - laser surface alloying - use of laser in mechanical

        A controlled amount of melting of work piece surface to the desired thickness using laser beam with the addition of powdered alloying elements in equal interval of time is called as laser surface alloying.

2. Laser cladding

01 - laser cladding - process of cladding

           A very thin layer of work piece melts when the beam of laser is applied on the surface. This thin layer of metal mixes with the cladding alloy and forms a metallurgical bonding in between the cladding and subtracts by freezes.

01 - laser cladding method - process of cladding


1. Using laser radiation and doing heat treatment is very fast.

2. Comparing to other heat treatment process, lasers are able to do heat treatment in a particular spot where other process are inaccessible.


          Welding is a process of joining or combining two or more metal pieces into a single unit.

01 - laser welding process - use of laser in welding

        If we consider welding of two metal plates, the metal plates will be held in contact at their edges and the laser beam will be allowed to move along the line of contact of the two plates.

       The laser beam will heat the edges of the two plates to their melting point and it will join them together.


1. Impurities will not be present between the joints, because it is a contact- less process.

2. Because of rapid cooling the heat affected zone is relatively small.

3. Laser welding can be done without any difficulties even in small places.

4. This welding is usually done in very high rates.

5. Even different types of metals can be welded.

6. The work piece will not get distorted, so the total amount of input is very small when compared to other welding processes.


       Laser cutting means evaporation or vaporization of the material at a point by focusing the laser beam.

01 - laser cutting - use of laser in cutting process

       The laser cutting setup is shown in the figure. The exothermal reaction between the metal and the gas provides the required energy for cutting. Gas jet helps in removing the vaporized materials.

       The cut metal’s adjacent edges are also cooled with the help of gas jet. Hence, the gas blow reduces the requirement of laser power, it also increases the depth and speed of cutting and a high quality cut will be provided.


1. Laser cutting can be done at room temperature and pressure without preheating and vacuum condition.

2. The microstructure of surrounding layers are not affected since heat affected zone is very small.

3. High cutting speed can be obtained.