What is drilling machine

A drilling machine is one of the most important machine tools in a workshop is a material removing or cutting process in which the tool uses a drill bit to cut into solid materials a hole of circular cross-section.

While performing drilling operation rotating edge of a cutting tool known as the twist drill which exerts a large force on the work clamped on a table.

The Egyptians drilled holes about 3000 years ago by bow drills in 1200 B.C.

There are different types of drilling machine used to perform the drilling operation which is following below. 


Types of  Drilling Machine :

1. Portable drilling machine
2. Sensitive drilling machine
3. Upright drilling machine
4. Radial drilling machine
5. Gang drilling machine
6. Multiple spindle drilling machine
7. Automatic drilling machine
8. Deep hole drilling machine

Drilling machine Operations :

1. Drilling
2. Reaming
3. Boring
4. Counterboring
5. Countersinking
6. Spot facing
7. Tapping
8. Lapping
9. Grinding
10. Trepanning

Types of the drill commonly used are : 

• Flat or spade drill
• Straight fluted drill
• Two-lip twist drill

Parallel shank (short series or "Jobbers" twist drill)
Parallel shank (stub series) twist drill
Parallel shank (long series) twist drill
Taper shank twist drill

• Taper shank core drill
• Oil tube drill
• Centre drill

Drill Size :

Drills from 0.2 to 100 mm are commonly produced in the metric system.

In the British system, drills are manufactured in three different sizes.

1. Number Sizes :

The drill size range from No. 1 to No. 80. 

Number 80 is the smallest having diameter equal to 0.0135 inches and the number 1 is the largest diameter equal to 0.228 inches.

2. Letter sizes :

The drill size range from A to Z.

A being the smallest having diameter equal to 0.234 inches and Z being the largest having diameter equal to 0.413 inches.

3. Fractional sizes :

The drill sizes range from 1/64 inch to 5 inches.

Designation of Drill :

Twist drills are designated in the Indian standard system by the series they belong to, the diameter, the I.S. Number and drilling material.

The drill is made in three types, namely, normal (N), hard (H), soft (S).

Thus a long-series 10 mm dia parallel shank twist drill conforming to I.S. Standard, made from carbon steel, type S and point angle 80 degrees are designated as follows. 

Parallel shank twist drill (Long) 10.00 - IS:599-CS-S-80


Drill Material :

For one piece of construction, high-speed steel or carbon steel are used. 

For two-piece of construction and cutting portion, high-speed steel is used.
For two-piece of construction and shank portion carbon steel with a minimum tensile strength of 70 kg per sq mm.

High-speed drills are more widely used due to its greater cutting efficiency.


Cutting Speed :

The cutting speed in a drilling operation is the peripheral speed of a point on the surface of the drill in contact with the work.

It is usually expressed in meters per minute.

 v = Π d n /1000 m per min

Where d is the diameter of the drill in mm and n is the r.p.m of the drill spindle.

Cutting speed of drill depends on several factors which are following below. 

• The kind of material is being drilled. Softer material the higher the speed.
• The cutting tool material. 

For example - Drill of high-speed steel can be operated at about twice the speed of drill of high carbon steel.

• The efficient use of cutting fluid.
• The quality of the surface finish desired.
• The method of holding the work.
• The size, type, and rigidity of the machine.

Feed :

The feed of a drill is the distance the drill moves into the work at each spindle revolution.

The feed per minute may be defined as the axial distance moved by the drill into the work per minute.

Sm = Sr × n

Sm = Feed per minute in mm.
Sr = Feed per revolution in mm.
n = r.p.m of the drill.

The amount of feed is depending upon :

• Material being cut 
• The rigidity of the job and machine
• Depth of hole
• Type of finish desired
• Power available
• Range of feed available

Depth of cut :

Depth of cut in drilling is equal to one half the diameter of the drill.

Thus if d be the diameter of the drill the depth of cut (t) is expressed as :

t = d / 2 mm

What is torque

The net force acting on a body accelerates it and takes something to give the body an angular acceleration. It needs a force, but it needs to be applied in a way that creates a twisting or turning action. Torque, τ is the rotational version of force and results from the application of one or more forces and is specified relative to a chosen rotation axis or pivot.

Torque is a measure of how much force an object act causes the object to rotate.

Torque is dependent upon :

• The distance from the rotation axis to the force application point (Refer to the first figure).
• The magnitude of the force, F.
• The orientation of the force relative to the displacement from the axis to force application point (Refer to the second figure).

Definition: 

The torque that a force produces is defined by 

τ = R x F 

τ = R x F sinθ

In other words, torque is the cross product between the vector of distance (the distance from the pivot to the point where force is applied) and the vector of force, 'θ' being the angle between r and F.

Example :

Let’s say we’re using a 0.5m long wrench to tighten a wheel nut, and we need to lean on the far end of the wrench with a force of 50 Newtons to do it up tightly. Simply multiplying the two numbers give us the required torque figure in Newton meters.

Torque τ = 50 (N) x 0.5 (m) x = 25 Nm

The SI units of torque are Newton-meter (N.m).

Rotational Equilibrium is analogous to transnational equilibrium, where the sum of the forces is equal to zero. 

There may be more than one force that acts on an object, and each of these forces may act on an object at a different point. Then every force is going to cause torque. The net torque is the sum of the torques in each case.

The sum of the torques is equal to zero in rotational equilibrium. In other words, the object does not have a net torque.

∑τ = 0

What is mechanical spring?

Spring is defined as an elastic machine element that deflects under the load action and returns to its original shape when the load is removed.

Functions of spring 

• To absorb shock and vibration
• To store energy
• To measure force
• Spring is used to apply force and control the motion

Types of Spring 

Spring is classified by its shape may be a wire helical coil. The most popular type of spring is the helical spring.

Helical spring is sometimes classified as spring close-coiled and spring open-coiled.

1. When the spring wire is coiled so close and its helix angle is very small, a helical spring is said to be close-coiled spring. Usually, a helix angle is less than 10 degrees.
2. A helical spring is said to be open-coiled spring, when the spring wire is coiled in such a way, that there is a large gap between the adjacent coil and its helix angle is large. Usually, a helix angle is more than 10 degrees. 

Two basic types of helical springs are following below :

1. Compression Spring
2. Extension Spring

Both this type of helical spring have the following advantages :

• They are easy to manufacture.
• They are cheaper than other types of spring.
• Their reliability is high.
• The deflation of spring is linearly propositional to the force acting on the spring. 

Due to the above advantages, the helical spring is popular and extensively used in a number of applications.

Helical Spring

Helical Torsion Spring 

The term torsion is somewhat misleading because the wire is subjected to bending stress.

The construction of this type of spring is similar to that of the compression or extension spring, expect the ends to be formed in such a way that the spring is loaded around the axis of a coil by a torque.

The helical torsion spring is used to transmit torque in the machine to a specific component. Helical torsion spring is used in door-hinges, brush-holders, starters for automobiles and door locks.

Helical torsion spring

Multi-leaf or Laminated Spring 

This spring is made up of a series of flat plates, usually in the semi-elliptical form. The flat plates are called leaves, the length of the leaves varies, the leaves are held together by means of U-bolts and a centre clip.

The longest leaf is called the master leaf and it bends at the both of two ends. The leaves of multi-leaf springs are subjected to bending stress. 

Multi-leaf spring is commonly used for vehicle, truck and rail wagon suspension.

Multileaf spring

Advantages and disadvantages of power screw

A power screw is a drive for converting rotary motion into a linear motion for power transmission in a machine. A power screw is also sometimes referred to as a translation screw. Instead of holding the parts together, it uses helical screw motion to transmit the power. Now in this article, you can check out the pros and cons of the power screw to understand more about it. 

Advantages of power screw:

• Large load-carrying capacity.
• Simple to design.
• Compact construction.
• Easy to manufacture.
• By applying small effort as 400 N, a load of 15 KN can be raised.
• Gives smooth and noiseless service without any maintenance.
• Self-locking property.
• Precise and accurate linear motion.

Disadvantages of power screw:

• Very poor efficiency is as low as 40%.
• It can be used for intermittent motion.
• High friction in threads causes rapid wear.

What is power screw

A power screw is a mechanical device used to convert rotary motion into linear motion and transmit power.

The power screw has three main parts such as screw, nut, and a part to hold either the screw or the nut. 

The power screw operates in two different ways depending on the holding arrangement. 

• In its bearing, the screw rotates, while the nut has axial motion.

The lathe's lead screw is an example of this category.

• The nut is kept stationary and screw moves in the axial direction 

Screw Jack and Machine Vice are examples of this category.

Applications of power screw : 

The main application of the power screw is the following below.

• To raise the load. Example - Screw-jack
• To obtain accurate motion in machining operations. Example - The lead screw of a lathe
• To clamp a workpiece. Example - Vice
•  To load a specimen. Example - Universal testing machine

Reference Books of Refrigeration and Airconditioning

1. Refrigeration and Air Conditioning by C. P. Arora FLIPKART
2. Basic Refrigeration and Air Conditioning by Ananthanarayanan FLIPKART
3. Refrigeration and Air Conditioning by G.F. Hundy, A.R.Trott, T.C. Welch FLIPKART
4. Refrigeration and Air Conditioning by Ameen Ahmadul FLIPKART
5. Refrigeration and Air Conditioning by W.F. Stoecker J.W. Jones FLIPKART 

Reference Books of Theory of Machine

1. Theory of Machines by Thomas Bevan FLIPKART
2. Theory of Machines by R.S. Khurmy, J.K. Gupta FLIPKART 
3. Theory of Machines by S S Raran FLIPKART

Reference Books of Thermodynamics

1. Engineering Thermodynamics by Nag P. K FLIPKART
2. Engineering Thermodynamics by M. Achuthan FLIPKART 
3. Thermodynamics: An engineering approach by Yunus A. Cengel, Michael A. Boles FLIPKART 
4. Fundamentals of Engineering Thermodynamics by M. J. Moran and H. N. Shapiro FLIPKART
5. Principle of Engineering Thermodynamics by Moran, Shapiro, Boettner, Bailey FLIPKART
6. Fundamentals of Thermodynamics by Sonntag R. E, Borgnakke C., and Van Wylen G. J FLIPKART
7. Applied Thermodynamics by Eastop FLIPKART

Reference Books of Fluid Mechanics

1. Fluid Mechanics by Fox FLIPKART
2. A Textbook of Fluid Mechanics and Hydraulic Machines by R.K.Bansal FLIPKART
3. Fluid Mechanics by V.L. Streeter FLIPKART
4. Fundamentals of Fluid Mechanics by A.L. Prasuhn FLIPKART
5. Introduction of Fluid Mechanics and Fluid Machines by Biswas FLIPKART 
6. Fluid Mechanics and Hydraulic Machines by K Subramanya FLIPKART 

Reference books of Strength of Material

1. Strength of Materials by Bhavikatti FLIPKART 
2. Mechanics of Structures by Junarkar S.B. FLIPKART
3. Strength of Materials Vol. I by S.P. Timonshenko FLIPKART
4. Strength of Materials Vol.II by S.P. Timonshenko FLIPKART
5. Strength of Material by S. Ramamrutham FLIPKART 
6. Strength of Material by R.S. Khurmi N Khurmi FLIPKART 
7. Engineering Mechanics of Solids by Egor. P.Popov FLIPKART
8. Advanced Mechanics of Solids by Srinath L.N FLIPKART

Reference Books of Solid Mechanics

1. An Introduction to Mechanics of Solids by S.H. Crandall, N.C. Dahl and S.J.Lardner FLIPKART
2. Theory of Elasticity by Timoshenko S.P. and Goodier J.N. FLIPKART
3. Solid Mechanics by S.M.A. Kazimi FLIPKART
4. Introduction to Mechanics of Solids by E.P. Popov FLIPKART
5. Mechanics of Solids by Arbind Kumar Singh FLIPKART

Reference Books of Engineering Graphics and Drawaing

1. Engineering Drawing and Graphics by K. Venugopal FLIPKART
2. Engineering Drawing by N.D. Bhatt and V.M. Panchal FLIPKART
3. Engineering Graphics by B. Bhattacharyya FLIPKART

What is factor of safety

In machine design, while designing the component, it is necessary to provide sufficient reserve strength in case of an accident so this is achieved by taking a suitable factor of safety.

fs = Failure stress / Allowable stress

fs = Failure load / Working load

The magnitude of the factor of safety depends upon the following factors:

• Effect of failure 
• Types of load
• A degree of accuracy in force analysis
• Material of component
• Reliability of component
• Cost of component
• Testing of the machine element
• Service conditions
• Quality of manufacture

Points mention below the following condition where a higher factor of safety is chosen :

• Magnitude and nature of external forces acting on the machine component cannot be precisely estimated.
• The material of the machine component has a non-homogeneous structure.
• The component of the machine is subject to the force of impact in service.
• There is a possibility of residual stresses in a machine component.
• The machine part is subjected to a high temperature during operation.
• In applications such as aircraft components, higher reliability is required.
• There is a possibility if abnormal variation in external load on some occasions.
• The machine part's manufacturing quality is poor.
• There is stress concentration in a machine component.

A higher factor of safety increases the component's reliability.

Factors to be considered during machine design

In machine design, there are so many factors to consider when designing the machine because the small amount of machine error leads to a high amount of loss so it is better to take care of some factor when designing the machine.

The list of these factors is given below :

• Cost
• High output and efficiency
• Strength
• Stiffness or rigidity
• Wear resistance
• Lubrication
• Operational safety
• Ease of assembly
• Ease and simplicity of disassembly
• Ease and simplicity of servicing and control
• Lightweight and minimum dimensions
• Reliability
• Durability
• Economy of performance
• Accessibility
• Processability
• Compliance with state standards
• The economy of repairs and maintenance
• Use of standard parts
• Use of easily available materials
• The appearance of the machine
• Number of machines to be built

Types of thermodynamic process

Introduction of thermodynamic process : 

Before going to study the thermodynamic process and types of thermodynamic processes, let us understand the meaning of the thermodynamic state of the system. The system has a certain temperature, pressure, volume, etc. characteristics. The present values of the system property are called the thermodynamic state of the system. 

Thermodynamic process :

When the system undergoes a change from one thermodynamic state to final state due change in properties such as temperature, pressure, and volume etc the system is said to have undergone the thermodynamic process. Types of the thermodynamic process described below. 

In simple word, a thermodynamic process occurred when the system changes from initial state to the final state.

• Process - Adiabatic 

Properties held constant - Heat energy 

• Process - Isenthalpic 

Properties held constant - Enthalpy

• Process - Isentropic 

Properties held constant - Entropy, Heat energy, Equilibrium 

• Process - Isobaric 

Properties held constant - Pressure 

• Process - Isochoric 

Properties held constant - Volume 

• Process - Isothermal   

Properties held constant - Temperature

• Process - Isotropic 

Properties held constant - Direction 

• Process - Polytropic 

Properties held constant - PVⁿ = C

• Process - Reversible 

Properties held constant - Entropy, Equilibrium 

Adiabatic process:  

An adiabatic process occurs when no heat can flow between a thermodynamic system and its surroundings. 

In this process Q = 0.

Example - Vertical flow of air in the atmosphere, Air expands and cools as it rises, and contracts and grows warmer as it descends. 

Isenthalpic process : 

An isenthalpic process is also called isoenthalpic process. It is a thermodynamic process in which enthalpy is constant. 

In this process H = 0. 

Example - Throttling process, consider the lifting of a relief valve or safety valve on a pressure vessel.

Isentropic process :

An isentropic process is an idealized thermodynamic process in which both adiabatic and reversible. 

It is a process in which entropy remains constant. 

In this process ΔS  = 0.

Example - Some isentropic thermodynamics device such as pumps, gas compressors, turbines, nozzles, diffusers.

Isothermal process :  

An isothermal process is a change of a system, in which the temperature of the system stays constant but heat may flow in or out of the system during an isothermal process. 

In this process ΔT = 0.

Example - Condensation, All the reactions going on in the refrigerator as a constant temperature is maintained in it, Melting of ice at zero degrees, and heat pump. 

Isochoric process :  

An isochoric process as the name suggests iso means same and choric means volume also called constant-volume process or isovolumetric process or isometric process. 

It is a thermodynamic process during which the volume of the closed system is kept constant.

In this process ΔV = 0.

Example - Heating of a gas in a closed cylinder.

Isobaric process : 

An isobaric is a thermodynamic process where the pressure of the system stays constant. 

In this process  ΔP  = 0.

Example: Heating of water in an open vessel and the expansion of a gas in a cylinder with a freely moving piston.

Isotropic process : 

The isotropic process is one that the permittivity ε and permeability μ of the medium is uniform in all directions of the medium. 

Example - Glass and metals are examples of isotropic materials. 

Reversible processes :  

A reversible process is a process whose direction can be reversed by including infinitesimal changes to some property of the system via its surroundings. In thermodynamics, throughout the entire process, the system is in thermodynamic equilibrium with its surroundings.

Example - Frictionless relative motion, and expansion and compression of spring.

Polytropic Process :

A polytropic is a thermodynamic process that obeys the relation where p is the pressure, V is volume, n is the polytropic index and C is a constant. The equation of this process describes multiple expansion and compression processes which include heat transfer. 

PVⁿ = C

From this relationship, we can arrive at relationships for several other types of a thermodynamic process.

• When n = 0 the process is isobaric
• When n = 1 the process is isothermal
• When n = k the process is isentropic
• When n = ∞ the process is isochoric

Example - Expansion of the combustion gasses in the cylinder of a water-cooled reciprocating engine.