Q.8 Briefly describe drilling. Explain operation performed on drilling machine.
Related Questions -
Q. Explain the following drilling operations:
(i) Countersinking
(ii) Reaming
(iii) Tapping
(iv) Counter boring (AKTU - 2012 - 13)
Ans. Drilling: - (AKTU - 2010 - 11)
Drilling is the cutting process of using a drill bit in a drill to cut or enlarge holes in solid materials, such as wood or metal. Different tools and methods are used for drilling depending on the type of material, the size of the hole, the number of holes, and the time to complete the operation.
In other words. Drilling is a cutting process in which a hole is originated or enlarged by means of a multipoint, fluted, end cutting tool. As the drill is rotated and advanced into the workpiece, material is removed in the form of chips that move along the fluted shank of the drill.
A very commonly used drilling machine used for light and precision work and normally availbale in a training workshop. The main parts include a column, base, swivelling table, table clamp, spindle, vertical feed handle and spindle drive mechanism at the top shown in figure. The cutting tool (a drill bit) is held in the drill chuck and vertical movements given to it by means of the Feed Handle to feed the revolving tool into the workpiece, held on the machine table, to drill the required hole.
Operation Performed by Drilling Machine: -
1. Drilling : Operation of producing a cylindrical hole in a solid body by means of a revolving tool, called Drill.
2. Reaming : Operation of finishing a drilled hole by means of a tool called Reamer.
3. Boring : Operation of enlarging a drilled hole, correcting its size and providing better finish by using a Boring tool.
4. Counter Boring : Operation of enlarging a drilled hole only to a limited length by means of a Counter Boring Toll.
5. Counter -Sinking : Operation of enlarging the top end of a drilled hole and giving it a conical shape by means of a Countersinking Tool.
6. Spot Facing : Operation of squaring up the surface at the top end of a hole to provide a true seat to a bolt head or collar.
7. Tapping : Operation of providing internal threads in a hollow component with the help of a Tap. Alternatively, a Collapsible Tapping Attachment can be used in place of a simple Tap.
Q.9 What is grinding? Describe the working principle of a grinding machine.
Ans. Grinding is the process of removing metal by a revolving wheel containing abrasive particles on the surface of a workpiece in the form of fine chips or dust particles by abrasive action. The grinding wheel are embedded with abrasive particles which act as cutting elements. The abrasives have high resistance to wear and heat. Abrasive particles (grains) are held together by bonding materials to form the cutting tool. Grinding gives a good surface finish and accuracy of high order. Grinding wheel are mounted on a grinding machine and is rotated at a high speed.
Different Method of Grinding :
(a) Surface Grinding: In surface grinding, the grinding wheel is made to rotate on a spindle and the work mounted on a reciprocating table is brought in contact with the grinding wheel. The material removed during grinding is in the form of powder chips.
(b) Cylindrical Grinding : In cylindrical grinding, the workpiece is held between the centres and is rotated at a much lower speed in a direction opposite to that of grinding wheel. This process is used to produce external cylindrical surfaces.
(c) Internal Grinding : It is similar to other rotational grinding operations except that as the part rotates, the internal surfaces are ground by a smaller grinding wheel.
(d) Centre Less Grinding : In this operation, there is a grinding wheel and a governing (or regulating) wheel. The part sits in between the wheels and is ground by grinding wheel. The regulating wheel slows down the rotation of the part so that it may not spin at same speed as the grinding wheel and reduce the rotational speed of grinding operations.
Centre less grinding is further divided in three groups :
(a) Through feed-grinding, (b) In feed grinding, (c) End feed grinding
Related Questions -
Q. Explain the following drilling operations:
(i) Countersinking
(ii) Reaming
(iii) Tapping
(iv) Counter boring (AKTU - 2012 - 13)
Ans. Drilling: - (AKTU - 2010 - 11)
Drilling is the cutting process of using a drill bit in a drill to cut or enlarge holes in solid materials, such as wood or metal. Different tools and methods are used for drilling depending on the type of material, the size of the hole, the number of holes, and the time to complete the operation.
In other words. Drilling is a cutting process in which a hole is originated or enlarged by means of a multipoint, fluted, end cutting tool. As the drill is rotated and advanced into the workpiece, material is removed in the form of chips that move along the fluted shank of the drill.
A very commonly used drilling machine used for light and precision work and normally availbale in a training workshop. The main parts include a column, base, swivelling table, table clamp, spindle, vertical feed handle and spindle drive mechanism at the top shown in figure. The cutting tool (a drill bit) is held in the drill chuck and vertical movements given to it by means of the Feed Handle to feed the revolving tool into the workpiece, held on the machine table, to drill the required hole.
Operation Performed by Drilling Machine: -
1. Drilling : Operation of producing a cylindrical hole in a solid body by means of a revolving tool, called Drill.
2. Reaming : Operation of finishing a drilled hole by means of a tool called Reamer.
3. Boring : Operation of enlarging a drilled hole, correcting its size and providing better finish by using a Boring tool.
4. Counter Boring : Operation of enlarging a drilled hole only to a limited length by means of a Counter Boring Toll.
5. Counter -Sinking : Operation of enlarging the top end of a drilled hole and giving it a conical shape by means of a Countersinking Tool.
6. Spot Facing : Operation of squaring up the surface at the top end of a hole to provide a true seat to a bolt head or collar.
7. Tapping : Operation of providing internal threads in a hollow component with the help of a Tap. Alternatively, a Collapsible Tapping Attachment can be used in place of a simple Tap.
Q.9 What is grinding? Describe the working principle of a grinding machine.
Ans. Grinding is the process of removing metal by a revolving wheel containing abrasive particles on the surface of a workpiece in the form of fine chips or dust particles by abrasive action. The grinding wheel are embedded with abrasive particles which act as cutting elements. The abrasives have high resistance to wear and heat. Abrasive particles (grains) are held together by bonding materials to form the cutting tool. Grinding gives a good surface finish and accuracy of high order. Grinding wheel are mounted on a grinding machine and is rotated at a high speed.
Different Method of Grinding :
(a) Surface Grinding: In surface grinding, the grinding wheel is made to rotate on a spindle and the work mounted on a reciprocating table is brought in contact with the grinding wheel. The material removed during grinding is in the form of powder chips.
(b) Cylindrical Grinding : In cylindrical grinding, the workpiece is held between the centres and is rotated at a much lower speed in a direction opposite to that of grinding wheel. This process is used to produce external cylindrical surfaces.
(c) Internal Grinding : It is similar to other rotational grinding operations except that as the part rotates, the internal surfaces are ground by a smaller grinding wheel.
(d) Centre Less Grinding : In this operation, there is a grinding wheel and a governing (or regulating) wheel. The part sits in between the wheels and is ground by grinding wheel. The regulating wheel slows down the rotation of the part so that it may not spin at same speed as the grinding wheel and reduce the rotational speed of grinding operations.
Centre less grinding is further divided in three groups :
(a) Through feed-grinding, (b) In feed grinding, (c) End feed grinding