MEE

235: Engineering
Technology

H.A. Ajimotokan (PhD),

Lecturer in Mechanical Process and Energy Engineering,
Dept. of Mechanical Engineering,
University of Ilorin, Ilorin, Nigeria.
Course Outline

❑ Unit 1: Introduction to Workshop

Practice,
❑ Unit 2: Industrial Safety,
❑ Unit 3: Machine Tools,
❑ Unit 4: Fabrication Technology,
❑ Unit 5: Use of Hand Tools, and
❑ Unit 6: Engineering Approach to
Design. (15h (T), 45h (P); 2C)
2
Course Objectives

The course provides students with basic workshop skills, which

would allow them to progress for further training and work in an
engineering workshop. At the end of the course, students should
be able to:
❑ List typical safety rules and work procedures in various workshops,
❑ Apply industrial safety policies and procedures,
❑ Identify the purpose of a range of simple hand and machine tools,
❑ Select and apply appropriate hand and machine tools, and tool
attachments for particular applications,
❑ Cut, weld, solder or braze materials in accordance with standard
practice,
❑ Specify safe engineering design for machine parts, device or
engineering process systems, and
❑ Build metal structures, machines or metal parts by cutting,
forming, joining and assembling processes.
3
UNIT 1: INTRODUCTION TO WORKSHOP
PRACTICE

❑ Contents Outline
1. Introduction
2. Objectives
3. Main Content
3.1 Plant and Workshop Layouts
3.2 Sections/ Types of Workshop
3.3 General Safety Rules and Work Procedures
in Workshops
4. Summary
4
1. Introduction

Engineering workshop is a place where products are manufactured

❑ through processes, operations or trades
❑ such as machining, bench work and fitting, welding, woodworking, etc

❑ Engineering workshop practice presents learners the opportunity to acquire

fundamental knowledge on the various processes.

❑ building learners competent in handling practical work in engineering

environment and
❑ acts as the basis for further technical studies. Workshop practice
requires the use of a number of simple machine and hand tools, and
considerable manual efforts.

❑ Various manufacturing processes performed in the engineering workshop

include the:

❑ cutting, filing, drilling, welding, tapping, and turning operations among

others. 5
1. Introduction Contd.

❑ The machine and hand tools used in the engineering workshop

depend on
❑ the types of required operations to be carried out.

❑ It is expected that whatever the tool used in any type of

operation,
❑ such should be done from the perspective of safety first.

❑ It is also important to know how to work safely in the workshop

❑ without causing damage to the equipment or injury to
yourself and your co-workshop user.

❑ In order to avoid accident in the workshop, every workshop

user needs to have a good technical know-how of any
equipment or tool before handling it.
6
1.1 Plant and Workshop Layout

Plant layout can be defined as a

❑ floor plan for determining and arranging machine and

hand tools, and equipment of the plant

❑ whether established or contemplated in a single best

place,

❑ to allow the quickest flow of material at the lowest

cost and with the least amount of handling in
processing the product,

❑ from the receipt of raw materials to the shipment of

the finished product. 7
1.1 Plant and Workshop Layout Contd.

❑ It starts with the design and position of the building,

and goes up to the location and movement of machine
worktables.

The workshop layout forms

❑ an integral part of factory planning or plant layout,
in which itself performs a more specialised job.

❑ All the manufacturing facilities like

❑ raw materials, machine and hand tools, fixtures,
and workers among others
❑ are provided an appropriate place in any
workshop.
8
1.1 Plant and Workshop Layout Contd.

In a best possible plant layout,

❑ material handling and its movement is
minimised and
❑ efficiently controlled; and

❑ points of bottlenecks, congestions, etc.

are gotten rid off such that raw materials
and semi-finished goods

❑ could move unhindered from one

workstation to the other. 9
1.1 Plant and Workshop Layout Contd.

The key goal of any layout is to maximise profits

❑ by creating the best possible arrangements of all

plant and workshop facilities,
❑ maximising the advantage of reducing the
production cost for the proposed product.

There are six principles of layout planning, which

are the principles of

❑ overall integration, minimum distance, flow,

cubic space, satisfaction and safety, and
flexibility. 10
1.1 Plant and Workshop Layout Contd.

The objectives of a good layout are to

❑ Reduce the production cost,

❑ Manufacture improved quality products,

❑ Evolve sufficient flexibility in the arrangement of

machine and hand tools, equipment and facilities (in
order to suit the minor future changes if any),

❑ Minimise materials handling and their movement,

❑ Provide smooth product flow and reduce work in

progress to minimum, etc. 11
1.1 Plant and Workshop Layout Contd.

Plant and workshop layouts can be classified into four basic

types, which are

❑ fixed, process, product, and combination layouts.

Fixed layout also called position or project layout - a layout in

which the main part of an assembly or material remains at a
fixed position.

❑ All its accessories, auxiliary material, machine and hand tools

required and the labour are brought to the fixed site to work.

❑ Thus, the product by virtue of its bulk or weight remains at

one location.
❑ The location of the major assembly, semi assembly
component and material is not disturbed till the product is
ready for dispatch. 12
1.1 Plant and Workshop Layout Contd.

❑ mainly adopted for extremely large items manufactured in

very small quantity such as ships, aeroplanes, boilers,

The main merit of this layout

❑ is the minimum movement of men, material, and tooling

during manufacturing process.

❑ It is highly flexible as the type of product and the related

processes could be easily altered without any alteration in
the layout.

The major demerits of this layout are that the

❑ cost of equipment handling is very high, labours and
equipment are difficult to utilise fully, and it is limited to
large items only. 13
1.1 Plant and Workshop Layout Contd.

Figure 1.1: Schematic illustration of a typical fixed layout

Process layout also called functional layout - a

layout in which arrangements of all similar
machine and hand tools, production facilities and
manufacturing operations are grouped together
according to their functions in separate sections. 14
1.1 Plant and Workshop Layout Contd.

This layout is adopted for

❑ batch or moderate production,

❑ specify the path for group technology and
❑ is typically preferred for job order type of
production and/ or maintenance activities of
non-repetitive type.

❑ Machine tools of one kind are arranged together

such that all the similar operations are
performed at the same place, e.g. all machine
tools for different kinds of turning and threading
operations in one section, etc. 15
1.1 Plant and Workshop Layout Contd.

❑ This type of layout does not necessarily

changes every time the product or
component changes.
❑ Moreover, the breakdown of any machine
does not affect the production process.

Figure 1.2: Schematic illustration of a typical process layout 16

1.1 Plant and Workshop Layout Contd.

Product layout also called line or straight line layout

- a layout in which all machines and production
facilities are arranged in a line, according to the
required sequence of operations for the
manufacture product.

❑ For examples each machine or section is arranged to

perform the next operation to be carried out by its
preceding machine or section.

❑ Workpiece starts from one end of production lines

and moves from one machine to the next along a
sequential path.
17
1.1 Plant and Workshop Layout Contd.

❑ It is mostly employed for assembling work.

❑ Product layout is advantageous for a

continuous production system where the
number of end products is small and the parts
are highly standardised and interchangeable.

❑ Suitable for products, getting a steady demand.

❑ Used for mass production, and ensures smooth

flow of materials and reduced material
handling. 18
1.1 Plant and Workshop Layout Contd.

❑ Breakdown of any machine on the

layout may result in stoppage of
production.

Figure 1.3: Schematic illustration of a typical product layout 19

1.1 Plant and Workshop Layout Contd.

Combination layout also called group layout - a

layout in which the process and product layouts
are combined,

❑ maximising the advantages of both types of

layouts.

❑ Combination layout groups together in sections,

etc. a set of machine and hand tools, equipment
and facilities,

❑ such that each set or group is used to perform

similar operations to produce a family of
components. 20
1.1 Plant and Workshop Layout Contd.

❑ Most manufacturing industries

adopt this type of layout.

Figure 1.4: Schematic illustration of a typical combination

layout 21
1.2 Sections/ Types of Workshop

There are various sections or types of workshop. The basic

ones are

❑ machine, fitting, woodwork or carpentry, forging, foundry,

welding and numerical control sections or shops among
others.

Machine shop is a place where metal parts are cut to the

required sizes and shapes, and then join together to form
mechanical units or machines.

❑ The machines so made are to be used directly or

indirectly in the production of necessities and luxuries
of civilisation.
❑ Machine shop is the base of all mechanical production and
machinists manage it. 22
1.2 Sections/ Types of Workshop Contd.

Fitting shop is a place where fitting or assembling

work is carried out.

❑ Some repairs and/ or maintenance, and die

punch work is also carried out in a fitting shop.

Woodwork or carpentry shop is a place where the

making of wooden components is carried out.

❑ Woodwork may be defined as the process of

making wooden components, which starts from a
marketable form of wood and ends with finished
products.
23
1.2 Sections/ Types of Workshop Contd.

It deals with the

❑ building work,
❑ pattern making for concrete or casting
work,
❑ furniture, cabinet making, etc.,
❑ joinery, i.e. preparation of joints.

Forging shop is a place where mechanical

working or shaping of metals in either cold or
hot state is carried out.
24
1.2 Sections/ Types of Workshop Contd.

❑ Forging is a mechanical working or shaping of

metals in either cold or hot state,

❑ which does not include machining,

grinding or casting.

❑ But in mechanical working of the metal, the

metal is actually shaped by pressure,

❑ in which forging, bending, twisting and/ or

drawing, among others is done, bringing it
to its final shape.
25
1.2 Sections/ Types of Workshop Contd.

Foundry shop is a place where desired

shape of metal is formed or obtained from
heated metal in its molten state.

❑ Foundry is one of the manufacturing

processes,
❑ in which metal of desired shapes can be
obtained from heated metal in its
molten (liquid) state, poured into mould
cavity. 26
1.2 Sections/ Types of Workshop Contd.

Welding shop is a place where

permanent fastening of two metals
is carried out.

❑ Welding is a process of permanent

fastening,

❑ in which two metals are fused at

a temperature of 3,200°C (when
metals are melted). 27
1.2 Sections/ Types of Workshop Contd.

Numerical control (NC)/ computer

numerical control (CNC) shop is a place
where the techniques for automation
of the operation of machine tool
components,

❑ based on coded instructions in the

form of alphanumeric and special
characters are carried out.
28
1.2 Sections/ Types of Workshop Contd.

NC is a mode of automatically controlling the

operation of machine tool components, based
on coded instructions in the form of
alphanumeric and special characters into the
system.

❑ T h e s y s t e m o p e r a t e s b y a b s t r a c t l y
programmed commands,

❑ encoded on a storage medium, as opposed

to manually controlled via hand wheels,
levers, or mechanically automated via
cams alone. 29
1.2 Sections/ Types of Workshop Contd.

❑ The system automatically interprets

these data and converts them to output
signals,

❑ which in turn, control different

machine components.

Most NC machines today are computer

numerically controlled;
❑ in which computers play an
integral part of the control. 30
4. Summary

The main purposes of engineering workshop practice are to

❑ present learners the opportunity to acquire fundamental

knowledge on the various operations involved in manufacturing,
❑ build learners competent in handling practical work in
engineering environment, and
❑ act as the basis for further technical studies.

The choice of the most appropriate technique for a specific job

requires the knowledge of all-possible manufacturing processes
- primary shaping, machining, joining and surface finishing
processes as well as processes effecting change in properties.

All forming and shaping processes except machining operations

would require additional manufacturing processes to produce
components with specific aesthetic characteristics. 31
4. Summary Contd.

Machining is any group of processes comprising material

removal and modification of the workpiece surfaces
after being manufactured by different methods.

Plant layout is a floor plan for determining and arranging

❑ machine and hand tools, and equipment of the plant
❑ whether established or contemplated in a single
best place,
❑ to allow the quickest flow of material at the lowest
cost and with the least amount of handling in
processing the product,
❑ from the receipt of raw materials to the shipment of
the finished product.
32
4. Summary Contd.

The workshop layout forms an integral part of

factory planning or plant layout, in which itself
performs a more specialised job.

Layouts can be classified into four basic types,

which are
❑ fixed, process, product, and combination
layouts.
❑ The various basic sections or types of
workshops are the machine, fitting, woodwork,
forging, foundry, welding and numerical control
sections or shops among others.
33
UNIT 2: INDUSTRIAL SAFETY

❑ Contents Outline
1. Introduction
2. Objectives
3. Main Content
3.1 What Industrial Safety is
3.3.1 Objectives of Industrial Safety
3.2 Accidents
3.2.1 Causes of Accidents
3.2.2 Types of Accidents
3.3 Personal Protective Equipment
3.4 Safety Rules
3.5 Fire and Safety
3.5.1 Classes of Fire
3.5.2 Types of Fire Extinguisher
4. Summary 34
1. Introduction

❑ Establishing policy on safety and work rules are critical

processes in the industry.

❑ Without adequate safety policies and procedures,

the industry may run at a colossal lost,
❑ as it is vulnerable to legal battles, downtime,
etc.

❑ Employers must train and orientate the employees,

❑ on the safety rules and

❑ available procedures, which would help to protect
both the employees and the employers. 35
3.1 What Industrial Safety is

Definitions of industrial safety mostly rally

❑ around policies and procedures

❑ that are put in place to safeguard workers and
equipment.

Industrial safety can be defined as the

❑ policies and protections that have been made

available to safeguard the factory and its workers
from hazards
❑ that could result in injury to personnel, damaged
to equipment or both. 36
3.1.1 Objectives of Industrial Safety

Objectives of industrial safety are to

❑ Educate all workers on safety

principles,
❑ Prevent accident in a plant by
eliminating hazard or reducing it to
the minimum,
❑ Prevent loss of life, permanent
disability, and loss of income of worker
by eliminating the causes of accident, 37
3.1.1 Objectives of Industrial Safety Contd.

❑ Eliminate accident that causes work

stoppage and production loss,

❑ Reduce all costs of accident, lower

w o r k e r ’s c o m p e n s a t i o n a n d
insurance rate,

❑ Improve production means to a

higher standard, etc.
38
3.2 Accidents

An accident is a mishap that causes injury to

worker, damage to tool or machine and
equipment.
❑ This injury could result in
❑ temporary or
❑ permanent disability of the worker.

3.1.1 Causes of Accidents

The causes of accidents can be categorised into
❑ mechanical,
❑ environmental and
❑ human causes. 39
3.1.1 Causes of Accidents Contd.

The mechanical causes could occur due to

❑ continued use of obsolete, not poorly
maintained or unsafe equipment,
❑ use of improperly guarded or unguarded
equipment, and
❑ improper or lack of use of safety devices,
among others.

The environmental causes could occur due to

❑ improper temperature and humidity - causing
workers’ fatigue, increasing the chances of
accident occurrence, 40
3.1.1 Causes of Accidents Contd.

❑ improper ventilation, defective and poor

illumination, and
❑ presence of dust, fumes and smoke,
among others.

The human causes could occur due to

❑ failure of using PPE,
❑ use of machine or equipment without
technical know-how, authority and safety
devices,
❑ long duration of work or shift duty, etc. 41
3.2.2 Types of Accidents

There are five basic types of accidents.

These include

❑ Near miss accident - an accident

without injury to worker or damage
of equipment,

❑ Trivial accident - an accident with less

injury to worker or damage of
equipment, 42
3.2.2 Types of Accidents Contd.

❑ Minor accident - an accident with

injury or damage more than the
trivial accident,

❑ Serious accident - an accident with

severe injury to worker or damage of
equipment, and

43
3.2.2 Types of Accidents Contd.

❑ Fatal accident - an accident with very

severe injury to worker or damage of
equipment.

❑ This may be causing permanent

disability or death.
3.3 Personal Protective Equipment
The fundamental approach to accident
prevention is by ensuring that the machine and
the environment are safe for work. 44
3.3 Personal Protective Equipment Contd.

However, the need to safeguard employees at all time by

ensuring that PPE/ devices are used always cannot be
downplayed.

❑ The PPE is classified based on the areas of application. These

include the

❑ Head protection equipment - are equipment used by employees

❑ liable to be hit by falling/ flying objects or exposed to head
injuries.
❑ Equipment such as the hard hat is worn to protect the
head.

Figure 2.1: The hard hat 45

3.3 Personal Protective Equipment Contd.

❑Face and eye protection equipment - are equipment

used during activities
❑involving flying particles, fillings, flashes and high
radiation.

❑It is advisable to wear face and eye protection

devices such as the eye or welding goggles to
protect the face.

(a) Welding shield (a) Operational eye shields (c) Welding goggles
Figure 2.2: The eye protective devices, showing the welding shield in (a),
46
eye shields in (b), and welding goggles in (c)
3.3 Personal Protective Equipment Contd.

❑ Ear protection equipment - worn to reduce the intensity of noise getting

into the ears.

❑Common types of ear protectors are the

❑earplug - a piece of wax, rubber, or cotton wool placed in the ear
as protection against noise, water, or cold air (see Figure 2.3 (a)),
❑ helmet (see Figure 2.3 (b)),
❑ earmuff (see Figure 2.3 (c)), and doughnut or cushion (see
Figure 2.3 (d)).

(a) Earplugs (b) Helmet

(c) Earmuffs (d) Doughnut ear cushion

Figure 2.3: The ear protective devices, showing the ear plugs in (a), helmet with earmuffs in (b), 47
ear muffs in (c), and doughnut ear cushion in (d)
3.3 Personal Protective Equipment Contd.

❑Hand protection equipment - provides the capability of

protection
❑against wetting, hot, molten or corrosive materials,
❑against sharp object from piercing the hand, and other
related risks to the fingers.

❑Equipment such as the gloves is worn to protect the hand.

(a) Cotton gloves (b) Rubber gloves

Figure 2.4: The hand protective equipment, showing the cotton gloves in (a), and rubber
gloves in (b) 48
3.3 Personal Protective Equipment Contd.

❑ Foot and leg protection equipment - provides the capability of

protection
❑ against wetting, against heavy objects fallen on the toes,
splashing of hot, molten metal or corrosive materials, and
other related risks to the feet or toes.

❑ The types of safety boot/ shoe also depend on the type of activity
being undertaken.

Figure 2.5: The safety boots, showing its various types 49

3.3 Personal Protective Equipment Contd.

❑ Body protection equipment - are cloths or straps

❑ worn to protect the human body from industrial

hazards.

❑ The body protection wears provide the capability of

protection against wetting or splashing of cold, hot,
molten metal or corrosive materials, fire, etc.

❑ The type of body protection worn by an individual

depends on the
❑ type of activity being undertaken. 50
3.3 Personal Protective Equipment Contd.

(a) Coverall

(b) Aprons

(c) Coats and boiler suits

(d) Fire blanket, cold suit, and safety belts

Figure 2.6: The body protective gadgets, showing the coveralls in (a), aprons in (b), coats and boiler suit in 51
(c) and fire blanket, cold suit, safety belts in (d)
3.3 Personal Protective Equipment Contd.

❑ Respiratory protective equipment - are equipment

used
❑ where the atmospheric air is contaminated and
may be hazardous to workers health.

❑The selection of respiratory protective equipment

often depends on factors such as the

❑ type of contaminant, its physical, chemical and

toxicological properties,
❑ frequency of exposure to the contaminant, etc. 52
3.3 Personal Protective Equipment Contd.

Figure 2.7: Different types of respiratory protective devices 53

3.4 Safety Rules

Safety rules outline the main activities to do or not to do

for completing a job safely and effectively.

Some of the basic safety rules, which could prevent hazards

in a working environment, are as follows:
❑ All guards must be kept in place,
❑ Never do anything unsafe to get the job done. If a job is
unsafe, it should be reported to the supervisor or
safety department,
❑ All safety warning signs must be placed at strategic
locations and must be obeyed at all times,
❑ Restrict unnecessary people from being in the work
area,
❑ PPE must be worn always in the work area, etc. 54
3.5 Fire and Safety

❑ Fire is an exothermic chemical reaction involving a heat

and light in a process where fuel organised substances
(heat and oxygen) are present.

Figure 2.8: The triangle of fire with essentials for combustion

55
3.5 Fire and Safety Contd.

❑ Figure 2.8 illustrates the triangle of fire. The essentials

of combustion includes the

❑ fuel - the biggest potential danger, which could

arises from leakage and exploration of hydrocarbon
(vapour or liquid);

❑ air - contains about 21% of oxygen, which is enough

for combustion to take place; and

❑ heat - the means of ignition, which may be in the

form of spark, naked flame, electricity, etc.
56
3.5.1 Classes of Fire

There are five classes of fire, which are the

❑ Class A fire - a type of fire that involves ordinary

combustible materials (excluding gases and liquids),
e.g. cloth, paper, rubber, etc.,

❑ Class B fire - a type of fire that involves inflammable

liquid/ liquid or liquefied fuel e.g. kerosene, petrol,
propane, wax, paint etc., excluding cooking oil and
grease, 57
3.5.1 Classes of Fire

❑ Class C fire - a type of fire that involves energised

electrical equipment such as motors, transformers,
and appliances. If the circuit of the Class C fire is de-
energised, it becomes any of the other classes of fire,

❑ Class D fire - a type of fire that involves the

combustible metal like magnesium, titanium,
aluminium, etc., and

❑ Class K fire - a type of fire that involves the grease,

cooking oil or animal fat.
58
3.5.2 Types of Fire Extinguisher and Suitability

The types of fire extinguishers include the

❑ Water and foam fire extinguisher - extinguishes fire by

eliminating the heat component of a fire triangle, while the
foam agents separate the oxygen from the other
components.

❑ suitable only for extinguishing Class A fire.

❑ Class B or C fire should not be extinguished with water
and foam extinguisher because
❑ its discharge stream could spread the flammable liquid
of a Class B fire or
❑ create a shock hazard in a Class C fire; 59
3.5.2 Types of Fire Extinguisher and Suitability Contd.

Carbon Dioxide fire extinguisher - extinguishes fire by

eliminating oxygen in a fire triangle and the heat with a
very cold discharge stream.

❑ suitable for extinguishing Classes B and C fire and

are typically not effective on a Class A fire;

Dry chemical fire extinguisher - extinguishes fire usually

by disrupting the chemical reaction of a fire triangle.
60
3.5.2 Types of Fire Extinguisher and Suitability Contd.

❑ Generally, the most commonly used type of

extinguisher

❑ Efficiently suitable for extinguishing

❑ Classes A, B, and C fire.

❑ It works by creating a barrier between the oxygen

and fuel components on a Class A fire.

❑ Ordinary dry chemical extinguishers are also

suitable for extinguishing Classes B and C fire; 61
3.5.2 Types of Fire Extinguisher and Suitability Contd.

Wet chemical fire extinguisher - extinguishes fire

by eliminating the heat of a fire triangle and
preventing re-ignition, using an agent that creates
a barrier between the oxygen and fuel elements.

❑ suitable for extinguishing modern, high

efficiency deep fat fryers fire - a Class K fire, in
commercial cooking operations.

❑ Also, some can be used to extinguish Class A

fire; 62
3.5.2 Types of Fire Extinguisher and Suitability Contd.

Halogenated or clean agent extinguisher - include the

halogen agents as well as the newer and less ozone
depleting halocarbon agents.

❑ They extinguish fire by disrupting the chemical reaction

of a fire triangle.

❑ Typically, the clean agent extinguisher is suitable for

extinguishing Classes B and C fire.

❑ Some clean agent extinguishers can also be suitable on

Class A fire; 63
3.5.2 Types of Fire Extinguisher and Suitability Contd.

Dry powder fire extinguisher - is similar to dry chemical

except that they extinguish fire by separating the fuel
from the oxygen component or by eliminating the heat
component of a fire triangle.

❑ Yet, dry powder extinguishers are suitable only for

extinguish Class D fire because they are inefficient
on any other class of fire; and

64
3.5.2 Types of Fire Extinguisher and Suitability Contd.

Water mist fire extinguisher - a recent advancement,

which extinguishes fire by eliminating the heat
component of a fire triangle.

❑ are alternatives to the clean agent extinguishers

where contamination is a concern.
❑ They are generally suitable for extinguishing Class A
fire,
❑ though they are, as well efficient for
extinguishing Class C fire.
65
4. Summary

❑ Industrial safety is defined as the policies and protections that

have been made available to safeguard the factory and its
workers from hazards that could result in injury to personnel,
damaged to equipment or both.
❑ Accident is a mishap that causes injury to worker, damage to
tool or machine and equipment.
❑ The causes of accidents are mechanical, environmental and
human causes.
❑ The five basic types of accidents are near miss, trivial, minor,
serious, and fatal accidents.
❑ The basic types of safety equipment or PPE used in industries
includes the
❑ head protection equipment e.g. helmet; 66
4. Summary Contd.

❑ face and eye protection equipment e.g. face shield, face

mask, eye goggles etc.;
❑ ear protection equipment e.g. earmuff, earplug;
❑ hand protection equipment e.g. hand gloves; respiratory
protection equipment e.g. respirators; body protection
equipment e.g. overall, aprons, lab coat etc.; and
❑ foot protection equipment e.g. safety boots, among others.
❑ Fire fighting is a way of putting out fire after its outbreak, which is
carried out using the fire fighting equipment and extinguishers,
depending on the class of fire that is involved.
❑ The five classes of fire are A, B, C, D, and K and the types of fire
extinguishers are water and foam, carbon dioxide, dry chemical,
wet chemical, halogenated, dry powder, and water mist
extinguishers. 67
Unit 3: Machine Tools

❑ Contents Outline
1. Introduction
2. Objectives
3. Main Content
3.1 Lathes
3.1.1 Types of Lathes
3.1.2 Functional Parts of a Lathe
3.1.3 Specifications of Lathes
3.1.4 Lathe Operations
3.1.5 Cutting Parameters
3.2 Milling Machines
3.2.1 Types of Milling Machines
3.2.2 Size of a Milling Machines
3.2.3 Depth of Cut
3.2.4 Types of Milling Operations
3.2.5 Operations Performed on Milling Machines
3.2.6 Dividing Heads
3.3 Screw Machines
3.3.1 Types of Screw Machines
3.3.2 Functional Parts of a Screw Machine
3.3.3 Different Operations of a Screw Machine
3.4 Fabrication Technology
3.4.1 Basic Fabrication Technology
3.4.2 Fabrication Project
68
4. Summary
1. Introduction

There are two basic types of tools, which are

generally used either in
❑ fabrication of projects and/ or as crafts.

❑ They are the hand and machine (or power) tools.

Machine tools are any of a class of power-driven

devices designed for carrying out specific machining
operations,

❑ to produce a desired size, shape and surface

finish of workpiece being machined. 69
1. Introduction Contd.

In other words, machine tools are power

operated device or system of devices,

❑ used to produce finish products of desired

size, shape and surface finish

❑ by removal of excess material in the form of

chips from the blanks with the help of cutting
tools moving past the workpiece surface.
70
1. Introduction Contd.

❑ Machine tools are characterised by higher

production accuracy compared with metal
forming processes.

❑ They are used for the production of relatively

smaller number of pieces; conversely, metal
forming processes are economical for producing
larger lots.

❑ Machine tools constitute about 70% of the total

operating production (or fabrication) machines. 71
1. Introduction Contd.

The productivity of a machine tool is measured

either by the
❑ number of parts produced in a unit of time,
❑ volumetric removal rate, or
❑ specific removal rate per unit of power consumed.

Productivity levels can be enhanced by:

❑ Increasing the machine speed and feed rates,
❑ Increasing the available power of the machine
tool, 72
1. Introduction Contd.

❑ Machining several workpieces or using several tools

simultaneously,
❑ Increasing the traverse speed of the operative units during
the non-machining parts of the production time,

❑ Increasing the level of automation for the machine tool

operative units and their switching elements,
❑ Adopting modern control techniques such as numerical
control (NC) and computer numerical control (CNC),

❑ Selecting the machining processes properly based on the

machined part material, shape complexity, accuracy, and
surface integrity, etc. 73
1. Introduction Contd.

Machine tools, according to their specialisation can be categories into:

❑ General-purpose (universal or standard) machine tools - any class of

power-driven devices,
❑ used for a variety of work and allows a wide range of machining
operation to be carried out;

❑ Special-purpose machines - any class of power-driven devices,

❑ designed for some particular purpose and performs only one or
a limited range of machining operations; and

❑ Limited-purpose machines - any class of power-driven devices,

❑ designed to perform a narrow range of operations on a wide
variety of products.
74
1. Introduction Contd.

The main functions of a machine tool are for

❑ holding the workpiece to be machined,
❑ holding the tool, and
❑ achieving the required relative motion to generate the
required part geometry.

Machine tools comprise

❑ a structure that is composed of a bed, column, or frame;
❑ slides and tool attachments,
❑ spindles and spindle bearings,
❑ a drive system (power unit),
❑ work holding and tool holding elements,
❑ control systems, and a transmission linkage. 75
1. Introduction Contd.

Machine tools, offer a broad range of tools to

choose from,
❑ some are very basic and others might be very
overwhelming to use.

❑ The word machine defines the tool that it has to

be powered by either A.C. or D.C. to operate.

❑ Machine tools powered using D.C, i.e. batteries,

seems to be growing more in popularity
❑ since there are no cords to contend with. 76
1. Introduction Contd.

In machine and woodwork shops among others,

❑ materials e.g. metals are cut to sizes and shapes on different
machine tools.

Examples of machine tools are the

❑ lathes, milling machines, screw machines, shaping machines,
grinding machines, drilling machines, machine vices, jig saw,
etc.

Using any tool, safety is a number one priority. All tools have
one thing in common, i.e. they can cause serious injury.
❑ Proper safety equipment should be worn at all times and all
safety procedures followed when operating any tool. 77
3.1 Lathes

Generally, lathe is considered to be the oldest

machine tool used in the industry and

❑ about one third of the machine tools operating in

engineering workshops.

A lathe is used to cut and shape engineering

materials

❑ by revolving the workpiece against a cutting

tool. 78
3.1 Lathes

❑ The workpiece is clamped either in a chuck,

❑ fitted on to the lathe spindle or in between the

centres.

❑ The cutting tool is fixed in a tool post, mounted on

a movable carriage that is positioned on the lathe
bed.

❑ The cutting tool can be fed on to the workpiece,

❑ either lengthwise or crosswise. 79
3.1.1 Types of Lathes

Lathes are manufactured in a variety of shapes and sizes,

❑ ranging from very small bench lathes - used for precision

work, to huge lathes - used for turning large steel shafts.
❑ However, the principle of operation of all types of lathes
is similar.

The different types of lathes are the

❑ speed, centre (or engine), bench, tool room, semi
automatic, automatic, and special purpose lathes

❑ Speed lathe - the simplest of all types of lathes in operation

and for fabrication. 80
3.1.1 Types of Lathes Contd.

The types of speed lathes are the

❑ woodworking, centering, polishing, and metal
spinning lathes.

A speed lathe is a simple lathe, in which the tools are

held against the work by hand.
❑ so named because of the very high speed of
headstock spindle.

The key components of speed lathe are the

❑ bed, headstock, tailstock, and tool post mounted on
an adjustable slide. 81
3.1.1 Types of Lathes Contd.

The speed lathe finds applications where

❑ cutting force is least such as in wood working and
preliminary metalworking operations, polishing,
winding, buffing etc.;

Figure 3.1: Pictorial illustration of a metal spinning speed lathe, indicating its parts 82
3.1.1 Types of Lathes Contd.

Centre (or engine) lathe - associated with the term

‘engine’

❑ because in the early days of its development, it was

driven by steam engine.

The centre lathes, which include the

❑ belt driven, individual motor driven, and gear head
lathes,
❑ are one of the most important members of the
lathe family, and
❑ the most widely used. 83
3.1.1 Types of Lathes Contd.

Like the speed lathe, it has all the basic parts, e.g., bed,
headstock, and tailstock among others.

But its headstock is

❑ much more robust in construction and
❑ contains additional mechanism for driving the lathe spindle
at multiple speeds.

Unlike the speed lathe, the centre lathe can feed the
cutting tool
❑ both in cross and longitudinal direction with reference
to the lathe axis
❑ with the help of a carriage, feed rod and lead screw; 84
3.1.1 Types of Lathes Contd.

Figure 3.2: Pictorial illustration of a centre lathe, indicating its principal parts

Bench lathe - a small lathe usually mounted on a bench.

❑ It has practically all the parts of a centre or speed lathe and it
performs almost similar operations.
❑ used for small and precision work; 85
3.1.1 Types of Lathes Contd.

Tool room lathe - a lathe that has features similar

to a centre lathe but much more accurately built.

❑ It has a wide range of spindle speeds, ranging

from a very low to a quite high speed up to 2,500
rpm.

❑ mainly used for precision work on

❑ tools, dies, gauges, and
❑ in machining workpiece where accuracy is
needed; 86
3.1.1 Types of Lathes Contd.

Semi automatic lathe - are Capstan and Turret lathes.

❑ Their developments result from the

❑ technological advancement of the centre lathe and
❑ are vastly used for mass production work.

❑ The distinguishing feature of this type of lathe is

❑ a hexagonal turret, which on its face could allow
multiple tools to be fitted and
❑ fed into the workpiece in proper sequence,
replacing the tailstock of a centre lathe. 87
3.1.1 Types of Lathes Contd.

❑ Due to this arrangement, multiple operations could be

carried out on a workpiece
❑ without re-setting of work or tools, resulting in
production of a number of identical parts at the
minimum time;

Automatic lathe - a high speed, heavy duty, and mass

production lathe, with complete automatic control.

A lathe, so designed that

❑ all working, workpiece handling and movements of
complete manufacturing process
❑ on a workpiece are done automatically, and 88
3.1.1 Types of Lathes Contd.

Special purpose lathe - a lathe designed for special

purposes and workpieces that cannot be
conveniently machined on a standard lathe.

❑ The types of special purpose lathes are the

❑ wheel, gap bed, ‘T’, and duplicating lathes.

❑ The wheel lathe is used for

❑ finishing the journals and
❑ turning the tread on railroad, car and
locomotive wheels. 89
3.1.1 Types of Lathes Contd.

The gap bed lathe,

❑ which has a removable section of the bed adjacent
to the headstock,
❑ is used to swing extra-large-diameter workpieces.

The T-lathe, which has a T-shape bed,

❑ is used for machining of rotors for jet engines.

Duplicating lathe is
❑ used for duplicating the shape of a flat or round
template onto a workpiece. 90
3.1.2 Functional Parts of a Lathe

A lathe comprises a bed,

❑ made of grey cast iron on which headstock, tailstock,
carriage and other components of a lathe are mounted.

❑ The main parts of a lathe are the

❑ bed,
❑ headstock,
❑ tailstock,
❑ carriage,
❑ feed mechanism, and
❑ thread cutting mechanism among others. 91
3.1.2 Functional Parts of a Lathe Contd.

Figure 3.3: Schematic configuration of a centre lathe, indicating its functional parts

Bed - is the base on which all other parts of lathe are

mounted.
❑ a massive and rigid single piece casting, made to
support other functional parts of the lathe. 92
3.1.2 Functional Parts of a Lathe Contd.

❑ The headstock of lathe is located on the left end of

the bed, while tailstock is located on the right side.

❑ The carriage of the machine rests over the bed and

slides on it.

❑ On the top of the bed, there are two sets of

guideways - inner and outer ways.
❑ The inner way provides sliding surfaces for the
tailstock while the outer way provides for the
carriage. 93
3.1.2 Functional Parts of a Lathe Contd.

❑ The bed is an essential part of the lathe,

❑ which must be strong and rigid because it carries all
parts of the machine and resists the cutting forces.

Headstock - its main function is to transmit power to the

different parts of the lathe. The headstock comprises the
❑ headstock casting to accommodate all the parts within
it,
❑ including gear train arrangement.

❑ The main spindle is adjusted on it,

❑ which possesses the live centre that the workpiece can
be attached. 94
3.1.2 Functional Parts of a Lathe Contd.

❑ The headstock supports the workpiece and revolves

with the fitted workpiece in the main spindle.

❑ The cone pulley is also attached to this

arrangement, which is used to get various spindle
speed through electric motor.

Tailstock - is used to support the right hand end of a

long workpiece.
❑ It may be clamped in any position along the
lathe bed. 95
3.1.2 Functional Parts of a Lathe Contd.

❑ Tailstock can be easily set or adjusted

❑ for alignment or non-alignment with respect to the

spindle centres and
❑ carries a centre called dead centre for supporting one
end of the work.

Figure 3.4: Schematic illustration of a centre lathe’s tailstock, indicating it main parts 96
3.1.2 Functional Parts of a Lathe Contd.

Carriage - is mounted on the outer guide ways of a lathe

bed, which could move in a direction parallel to the spindle
axis.

❑ It comprises important parts such as apron, cross-slide,

saddle, compound rest, and tool post.

❑ The lower part of the carriage is termed

❑ the apron, wherein there are gears to constitute apron

mechanism for adjusting the direction of the feed
❑ using clutch mechanism and the split half nut for
automatic feed. 97
3.1.2 Functional Parts of a Lathe Contd.

❑ The cross-slide is basically mounted on the carriage,

❑ which generally travels at right angles to the spindle
axis.

❑ On the cross-slide, a saddle is mounted wherein

❑ the compound rest could be adjusted, rotated and
fixed to any desired angle.

❑ The tool post is an important part of carriage,

❑ which fits in a tee-slot on the compound rest,
❑ which holds the tool holder in place by the tool post
screw. 98
3.1.2 Functional Parts of a Lathe Contd.

Figure 3.5: Schematic illustration of a tool post in a centre lathe

Lathe Accessories and Attachments - there are many

lathe accessories, which support the lathe operations.
❑ These include the
❑ centres, catch plates and carriers, chucks, collets,
faceplates, angle plates, mandrels, and rests. 99
3.1.2 Functional Parts of a Lathe Contd.

❑ They are used either for

❑ holding and supporting the workpiece or
❑ for holding the tool.

❑ Lathe attachments are additional equipment provided by

the lathe manufacturer together with the lathe, which are
used for specific operations.

❑ These attachments include

❑ stops, ball turning rests, thread chasing dials, milling
attachment, grinding attachment, gear cutting
attachment, turret attachment, and crank pin turning
and taper turning attachments. 100
3.1.2 Functional Parts of a Lathe Contd.

Lathe centres - most common method of holding

the workpiece on a lathe is

❑ between the two centres,

❑ generally, known as the live centre (headstock
centre) and dead centre (tailstock centre).

❑ They are made of very hard materials to resist

deflection and wear, and
❑ are used for holding and supporting cylindrical
workpieces. 101
3.1.2 Functional Parts of a Lathe Contd.

Carriers and Catch Plates - are used to drive a workpiece when it is

held between two centres.

❑ Carriers, also known as the driving dogs,

❑ are attached to the end of the work by a setscrew.

❑ Carriers are also used for holding and supporting workpiece.

Figure 3.6: Schematic illustration of a lathe dog, indicating its typical use on lathe 102
3.1.2 Functional Parts of a Lathe Contd.

❑ Catch plates are either

❑ screwed or bolted to the nose of the headstock
spindle.

❑ A projecting pin from the catch plate or carrier

❑ fits into the slot provided in either of them.

❑ This imparts a positive drive between the lathe spindle

and workpiece.

Chuck - is one of the most important devices for holding

and rotating of a workpiece on the lathe. 103
3.1.2 Functional Parts of a Lathe Contd.

❑ The chuck is basically attached to the

❑ headstock spindle of a lathe,
❑ through its internal thread,
❑ fitted onto the external thread on the spindle
nose.

❑ Workpieces of short, cylindrical, and hollow

objects or those of irregular shapes,
❑ which cannot be conveniently mounted
between centres, are easily and rigidly held in
a chuck. 104
3.1.2 Functional Parts of a Lathe Contd.

❑ The different types of lathe chucks are the

❑ three jaws (or universal), four jaws (or
independent), magnetic, collet, air (or hydraulic)
operated, combination, and drill chucks.

Faceplate - is employed for holding of workpieces,

❑ which cannot be conveniently held between
centres or by chucks.

❑ Faceplates possess the radial, plain and T slots

❑ for holding of workpieces by bolts and clamps. 105
3.1.2 Functional Parts of a Lathe Contd.

❑ They comprise a circular disc, bored out and

threaded to fit the nose of a lathe spindle.

❑ They are comprehensively constructed, accurately

machined and ground, and
❑ have strong thick ribs on their back.

❑ Faceplates have slots cut into them,

❑ thus nuts, bolts, clamps and angles are used
to hold the workpieces on them.
106
3.1.2 Functional Parts of a Lathe Contd.

Angle plate - is a cast iron plate,

❑ having two faces, machined to make them
absolutely at right angles to each other.

❑ Holes and slots are provided on both faces

❑ so that it may be clamped on a faceplate and can
equally hold the workpiece on the other face by
bolts and clamps.

❑ The plates are used in conjunction with a faceplate

❑ when the workpiece surfaces should be held
horizontal. 107
3.1.2 Functional Parts of a Lathe Contd.

Mandrel - is a device, made of hardened and tempered steel

shaft or bar with 60° centres,
❑ which enables it to be mounted between centres.

❑ Mandrels are used for holding and rotating a hollow

workpiece, which has been previously drilled or bored.

❑ The workpiece revolves with the mandrel,

❑ mounted between two centres.

❑ The mandrel is always rotated with the help of a lathe dog and
catch plate, and it then,
❑ drives the workpiece by friction. 108
3.1.2 Functional Parts of a Lathe Contd.

❑ It is never placed in a chuck for turning of the workpiece

and unlike an arbour,
❑ which is a cutting tool holder; mandrel is a work
holding device.

❑ Rest - is a lathe device,

❑ which supports a long slender workpiece,
❑ when it is turned between centres or by a chuck,
❑ at some intermediate point to prevent bending of
the workpiece due to its own weight and
❑ vibration of set up due to the cutting force that acts
on it. 109
3.1.2 Functional Parts of a Lathe Contd.

❑ The two types of rest commonly used for supporting long

workpieces on a centre lathe are the steady (or centre) and
follower rests.

3.1.3 Specifications of a Lathe

Generally, the size of a lathe is specified using parameters such as
the
❑ swing or maximum diameter of workpiece that can be
rotated over the bed ways,
❑ maximum length of the workpiece that can be held between
headstock and tailstock centres,
❑ bed length that may include headstock length, and
❑ maximum diameter of the bar that can pass through spindle
or collet chuck of capstan lathe. 110
3.1.3 Specifications of a Lathe Contd.

❑ The common lathe can also be specified by parameters such as

the
❑ maximum swing over bed,
❑ maximum swing over carriage,
❑ height of centres over bed,
❑ maximum distance between centres,
❑ length of bed,
❑ width of bed,
❑ Morse taper of centre,
❑ diameter of hole through spindle,
❑ faceplate diameter,
❑ size of tool post,
❑ number of spindle speeds, etc. 111
3.1.3 Specifications of a Lathe Contd.

A - Length of bed, B - Distance between centres, C - Diameter of the

work that can be turned over the ways, and D - Diameter of the work that can be
turned over the cross slide.
Figure 3.7: Schematic illustration of the parameters for specifications of a
lathe

3.1.4 Lathe Operations

❑ Lathes are employed for
❑ turning external cylindrical, tapered, and
contour surfaces; 112
3.1.4 Lathe Operations Contd.

❑ boring cylindrical and tapered holes,

❑ machining face surfaces,
❑ cutting external and internal threads,

❑ knurling, centring, drilling, counterboring,

countersinking, spot facing and reaming of holes,
❑ etc.

❑ Lathes are used in both work and mass

production.
113
3.1.4 Lathe Operations Contd.

(a) Common tools for lathe operation

(b) Common lathe operations

Figure 3.8: Schematic illustrations of lathe operations, showing common
tools for lathe operations in (a), and common lathe operations in (b) 114
3.1.4 Lathe Operations Contd.

In other to carry out the various machining

operations on a lathe,

❑ the workpiece is supported and driven by one or

combinations of the following methods:

❑ Workpiece is held and driven by chuck with

the other end supported on the tailstock,

❑ Workpiece is held between centres and driven

by carriers and catch plates, 115
3.1.4 Lathe Operations Contd.

❑ Workpiece is held on a mandrel, which is supported

between centres and driven by carriers and catch
plates, and
❑ Workpiece is held and driven by a chuck or a faceplate
or an angle plate.

These methods for holding the workpiece can be classified

under two headings,
❑ which are the work held between centres and
❑ by a chuck or any other fixture.

❑ The operations performed using a lathe are grouped into

three major categories. 116
3.1.4 Lathe Operations Contd.

❑ There are operations performed either

❑ by holding the workpiece between centres or

❑ by a chuck, e.g. straight turning, shoulder turning,
taper turning, chamfering, eccentric turning, etc.;
and

❑ operations performed
❑ by holding the workpiece by a chuck, faceplate or
angle plate,
❑ e.g. undercutting, parting-off, internal thread
cutting, reaming, etc 117
3.1.4 Lathe Operations Contd.

Turning - is a machining operation in which the material of

the workpiece is removed
❑ by a traversing cutting tool (or cutter),
❑ from the external or internal surface of a rotating workpiece,
❑ producing internal or external cylindrical shapes.

❑ The operation used for machining internal surfaces is often

called the boring operation in which a hole previously drilled
is enlarged.

❑ Figure 3.9 shows the basic turning operations with machining

parameters of cutting speed v, rotational speed n, depth of
cut t, undeformed chip cross-section area A and feed rate f. 118
3.1.4 Lathe Operations Contd.

❑ (a) Tapered turning

❑ (b) Straight turning

(c) Grooving (d) Thread cutting

Figure 3.9: Schematic illustrations of basic turning operations with machining
parameters, showing tapered turning in (a), straight turning in (b), grooving in (c), and
threading cutting in (d)
119
3.1.4 Lathe Operations Contd.

Threading - is the cutting of helical groove on a workpiece,

❑ which may be either on the internal or external
surfaces.

❑ Thread of any pitch, shape and size could be cut on a lathe

❑ using single point cutting tool.
❑ A specially shaped cutting tool, known as thread cutting
tool, is used for this purpose.

❑ Thread cutting using a lathe, is performed by

❑ traversing the cutting tool at a definite rate in
proportion to the rate at which the workpiece
revolves. 120
3.1.4 Lathe Operations Contd.

❑ Thread cutting is an operation for

❑ producing a helical groove on spindle shape
such as V, square or power threads on a
cylindrical surface.

Figure 3.10: Schematic illustration of a thread cutting on a lathe 121

3.1.4 Lathe Operations Contd.

Drilling - is an operation, using a twist drill,

❑ which produces holes that are axially located in cylindrical parts.

❑ For this operation, the workpiece is held in a chuck or on a faceplate.

❑ The drill is held in the position of the tailstock,
❑ moved towards the workpiece, thus, the drill is fed against the
rotating workpiece

Figure 3.11: Simplified illustration of a drilling operation on a lathe

122
3.1.4 Lathe Operations Contd.

Boring - is a machining operation,

❑ performed to enlarge a previously drilled hole with a single point
cutter.
❑ used when correct size drill is not available.
❑ However, it should be noted that boring could not make a hole.

Facing - is a machining operation,

❑ performed to create a smooth, flat face, accurately perpendicular
to the axis of the workpiece cylindrical part or its axis of rotation.

❑ For this operation, the workpiece may be held in a chuck and rotated
about the lathe axis.
❑ A facing tool is fed perpendicular to the axis of the lathe. The tool is
slightly inclined towards the end of the workpiece.
123
3.1.4 Lathe Operations Contd.

Knurling - is a machining process,

❑ in which a diamond shaped regular pattern of straight,
angled or crossed lines
❑ are cut, embossed, or rolled on the surface of a
workpiece.

❑ Knurling is carried out using a special knurling tool,

❑ which is made of a set of hardened steel rollers in a holder
with teeth cut on their surface in a definite pattern.

❑ The purpose of knurling is to provide an effective gripping

surface on a workpiece
❑ to prevent it from slipping when operated by hand. 124
3.1.4 Lathe Operations Contd.

Chamfering - is a machining operation,

❑ performed to cut transitional edge between two faces of
a workpiece.

❑ A chamfer is a transitional edge between two faces of an

object.
❑ It is also known as a bevel, but denotes more often cutting
and is more often 45° with respect to the two adjoining
faces.

❑ Chamfering is carried out on workpieces for

❑ better look, to enable nut pass freely on threaded
workpiece, to remove burrs and protect the end of the
workpiece from being damaged. 125
3.1.5 Cutting Parameters

❑ Common parameters used in description of cutting operations of a

lathe are the
❑ cutting speed, feed rate, and depth of cut.

❑ Cutting speed - refers to the speed at which the tool point of the
cutting tool moves with respect to the workpiece,
❑ measured in metre per minute.

❑ Machining at a correct cutting speed is highly important for good

tool life and efficient cutting.
❑ Too slow cutting speeds reduce productivity and increase
manufacturing costs
❑ while too high cutting speeds result in tool overheating and
premature failure of its cutting edge. 126
3.1.5 Cutting Parameters

❑ Factors that affect cutting speed depend upon the

❑ material of the workpiece,
❑ feed, depth of cut, type of operation,
❑ rigidity of machine tool and workpiece, and
❑ so many other cutting conditions like cutting tool material
and its shape, type of cutting fluid used, etc.

❑ Feed - is the rate at which the workpiece moves into the

cutting tool,
❑ measured in feed per tooth revolution.

❑ It is usually given as a linear movement per revolution of the

spindle or workpiece. 127
3.1.5 Cutting Parameters

Feed rate - is the movement of the tool cutting

edge along the bed,
❑ during one revolution of the workpiece,
measured in millimetre per revolution.

❑ Its value depends upon the depth of cut and

surface finish of the work desired.

❑ Depth of cut - is measured in the direction

❑ perpendicular to the axis of the workpiece for
one turning pass. 128
3.2 Milling Machines

❑ A milling machine is any of a class of machine tools that

❑ removes metal as the workpiece is fed against a
rotating multipoint cutter.

❑ The milling cutter rotates at high speed and it removes

metal at a very fast rate with the help of multiple cutting
edges.

❑ One or more number of cutters could be mounted

simultaneously on the arbour of milling machine.
❑ reason a milling machine finds wide application in
production work. 129
3.2 Milling Machines Contd.

❑ Milling machine is used for machining

❑ flat and contoured surfaces,
❑ external and internal threads, and
❑ helical surfaces of various cross-sections.

❑ It is used in a variety of industrial applications

❑ where complex shaping, large quantities of material
removal and accuracy is required.

❑ In many applications, due to its higher production rate

and accuracy, milling machine has even replaced shapers
and slotters. 130
3.2 Milling Machines Contd.

❑ In a milling operation, the workpiece is cut by means of

a rotating cutter,
❑ which has multiple cutting edges.

❑ For cutting operation, the workpiece is fed against the

rotary cutter.

❑ As the workpiece moves against the cutting edges of

milling cutter,
❑ metal is removed in chips form of trochoid shape.
❑ Machined surface is formed in one or more passes of
the workpiece. 131
3.2 Milling Machines Contd.

❑ The workpiece to be machined could be

❑ held in a vice, rotary table, three jaw chuck, index head,
between centres, special fixture or bolted to machine
table.

❑ The type of material to be machined determines the

❑ rotatory speed of the cutter and workpiece feed rate.

3.2.1 Types of Milling Machines

The milling machine may be classified in several forms, but the
choice of any particular machine is determined primarily by the
❑ size of the workpiece to be machined and operations to be
performed. 132
3.2.1 Types of Milling Machines Contd.

❑ With this function or requirement in mind, milling

machines are made in variety of types and sizes.

❑ According to general design, the types of milling

machines are the
❑ column and knee type, planer and special
types milling machines.

❑ Column and knee type milling machine - is the

most commonly used milling machine,
❑ which is used for general shop work. 133
3.2.1 Types of Milling Machines Contd.

❑ With this type of milling machine, the

❑table is mounted on the knee casting,
❑ which in turn is mounted on the vertical slides of the main
column.

❑ The knee is vertically adjustable on the column so that the

❑table can be moved up and down
❑ to accommodate workpiece of various heights.

❑ The column and knee type milling machines are classified based on
the
❑various methods of power supply to the table,
❑different table movements and various main spindle axes of
rotation. 134
3.2.1 Types of Milling Machines Contd.

❑ These include the vertical, horizontal, hand, and

universal milling machines.

Figure 3.12: Pictorial illustration of a column and knee type milling

machine, indicating its main parts 135
3.2.1 Types of Milling Machines Contd.

Planer type milling machines - a heavy duty machine,

❑ which resembles a planning machine.

❑ Like a planner, it has a cross rail capable of being raised or

lowered,
❑ carrying the cutters, their heads, and the saddles,
which are all supported by rigid uprights.

❑ There may be a number of independent spindles carrying

cutters on the rail as two heads on the uprights.

❑ use is limited to production work only and is

considered ultimate in metal removing capacity. 136
3.2.1 Types of Milling Machines Contd.

Special type milling machine - a milling machine

of non-conventional design,
❑ developed to suit special purposes.

❑ The features that they have in common with

other milling machines are the
❑ spindle for rotating the cutter and
❑ provision for moving the
❑ tool or workpiece in different directions.
137
3.2.2 Specifications of a Milling Machine

The size of the column and knee type milling

machine is specified by the

❑ dimensions of the worktable surface, and

❑ its maximum length of longitudinal, cross and
vertical travels.

❑ Number of spindle speeds, number of feeds,

❑ spindle nose taper, power available,
❑ floor space required and net weight of machine
may also be required for additional specification. 138
3.2.3 Depth of Cut

Depth of cut - in a milling operation, is defined as

❑ the thickness of the material removed in one pass of
workpiece under the cutter.

❑ Thus, it is the perpendicular distance measured

between the original and final surface of the workpiece,
expressed in mm.

3.2.4 Types of Milling Operations

❑ The two distinct methods of milling operations are
classified as the up-milling and down milling operations.
139
3.2.4 Types of Milling Operations Contd.

In the up-milling (or conventional milling) operation,

❑ the metal is removed in form of small chips by a
cutter,
❑ rotating against the workpiece direction of travel.

❑ In this type of milling, the chip thickness is minimum

at the start of the cut and maximum at the end of cut.

❑ As a result, the cutting force also varies

❑ from zero to the maximum value per tooth
movement of cutter. 140
3.2.4 Types of Milling Operations Contd.

The advantages of up-milling process are

❑ Does not require a backlash eliminator,
❑ Safer in operation (as the cutter does not climb on the
workpiece),
❑ Loads on teeth act gradually,
❑ Built-up edge fragments are absent from the machined
surface, and
❑ The milling cutter is not affected by the sandy or scaly
surfaces of the workpiece.

The main disadvantages of up-milling process are the

❑ lift tendency of the workpiece by the cutting forces from the
fixture and
❑ obtained poor surface finish. 141
3.2.4 Types of Milling Operations Contd.

❑ But being a safer process, it is commonly used method of

milling.

Figure 3.13: Schematic illustration of an up-milling process, indicating its

nomenclatures

In down (or climb) milling operation,

❑ the metal is removed by a cutter rotating in the same
direction of feed as the workpiece. 142
3.2.4 Types of Milling Operations Contd.

❑ The effect of that is the teeth cut downward and

❑ chip thickness is maximum at the start of cut and
minimum in the end.

❑ With this method, it is claimed that

❑ less friction is involved and
❑ consequently less heat is generated between the
contact surfaces of the cutter and workpiece.

❑ Down milling can be used advantageously on many kinds

of workpieces
❑ to increase the number of pieces per sharpening and
to produce a better finish. 143
3.2.4 Types of Milling Operations Contd.

❑ With down milling, the saws

❑ cut long thin slots more satisfactorily than the standard
milling.

❑ Other advantages are

❑ slightly lower power consumption is obtainable by down
milling because there is no need to drive the table against
the cutter,
❑ fixtures are simpler and less costly as cutting forces are
acting downward,
❑ flat workpiece or plate that cannot be firmly held can be
machined by down milling,
❑ cutter with higher rake angles can be used (decreasing the
power requirements), 144
3.2.4 Types of Milling Operations Contd.

❑ tool blunting is less likely, and

❑ down milling is characterised by fewer
tendencies of chattering and vibration
(leading to improved surface finish).

Figure 3.14: Schematic illustration of a down milling process,

indicating its nomenclatures
145
3.2.5 Operations Performed on Milling Machines

❑ Unlike a lathe, a milling cutter does not give

❑ a continuous cut, but begins with a sliding motion
between the cutter and workpiece.

❑ Then, follows a crushing movement, and a cutting

operation by which the chip is removed.

Many different kinds of operations can be performed on

a milling machine
❑ but a few of the more common operations are the
❑ plain milling, face milling, side milling, angular
milling and gang milling operations among others. 146
3.2.5 Operations Performed on Milling Machines Contd.

❑ Plain (or slab) milling - a method of producing a

plain, flat horizontal surface parallel to the axis of
rotation of the cutter.

❑ Face milling - a method of producing a flat surface

at right angles to the axis of the cutter.

❑ Side milling - is a machining process of producing

flat vertical surface on the side of a workpiece by
using a side milling cutter.
147
3.2.5 Operations Performed on Milling Machines Contd.

❑ Angular milling - a machining operation used for

producing a flat surface,
❑ making an angle to the axis of the cutter.

❑ Gang milling - a machining operation in which two or

more cutters with same or different diameters,
❑ mounted on the arbour of the milling machine, are
used simultaneously.

❑ Form milling - a machining operation used for producing

an irregular outline on the surface of a workpiece.
148
3.2.5 Operations Performed on Milling Machines Contd.

❑ End milling - a machining operation used for

❑ producing milling slots, flat surfaces, and
profiles on a workpiece using end milling cutter.

❑ Profile milling - a machining operation that involves

❑ the reproduction of a template outline or
complex shape of a master die on a workpiece.

❑ Saw milling - a machining operation used for

❑ producing deep slots and cutting materials into
the required length by slitting saws. 149
3.2.5 Operations Performed on Milling Machines Contd.

❑ T-slot milling - a machining operation used

❑ for cutting of T-passage on a workpiece.

❑ Keyway milling is a machining operation used

❑ for cutting of keyway on a workpiece.

❑ Gear cutting milling is a machining operation used

❑ for cutting of gear teeth on a workpiece.

❑ Helical milling is a machining operation used

❑ for producing or generating helical profile on a
workpiece. 150
3.2.5 Operations Performed on Milling Machines Contd.

❑ Flute milling - a machining operation used

❑ for grooving or cutting of flutes on drills, reamers, taps,
etc.

❑ Straddle milling - a machining operation used

❑ for milling two sides of a workpiece by employing two side
milling cutters simultaneously.

❑ Thread milling is a machining operation used

❑ for milling both internal and external threads on dies,
screws, worms, etc.
❑ As an alternative to the screw cutting on a lathe, this method is
being more extensively introduced in modern machine shops. 151
3.2.6 Dividing Heads

Dividing head is an attachment,

❑ which extends the capabilities of a milling machine.

❑ They are mainly employed on knee-type milling

machines to enhance their capabilities towards
❑ milling straight and helical flutes, slots, grooves, and
gashes;
❑ whose features are equally spaced about the
circumference of a blank.

❑ Such jobs include milling of spur and helical gears, spline

shafts, twist drills, reamers, and milling cutters etc. 152
3.2.6 Dividing Heads Contd.

❑ Thus, dividing heads are capable of indexing the workpiece

through predetermined angles.

❑ In addition to the indexing operation, the dividing head

continuously rotates the workpiece, which is set at the required
helix angle during milling of helical slots and helical gears.

❑ There are several versions of dividing heads. These include the

❑ plain milling dividing heads, mainly used for indexing milling
fixtures;
❑ universal dividing heads, optical dividing heads, commonly
used for precise indexing, and
❑ also for checking the accuracy of marking graduation
lines on dial scales. 153
3.3 Screw Machines

❑ Screw machine, more commonly known as automatic

lathe,
❑ serves the purpose of machining hard materials,
such as metal and plastic,
❑ through the use of a lathe and cutting tools known
as tool bits.

❑ Using the screw machines, small parts, such as screws,

could be made quickly and easily.

❑ Moreover, with the advent of CNC technology, the

whole machining operation is made even easier. 154
3.3 Screw Machines Contd.

❑ The total numbers of spindles available on a screw

machine affects the number of parts of the same or
different configuration,
❑ which could be machined simultaneously.

❑ When purchasing a screw machine, shoppers should

determine the
❑ type that best fits their work needs by determining the
❑ required production from the machine,
❑ types of raw materials to be machined to the final
products, and
❑ whether an automatic machine is required or not.
155
3.3.1 Types of Screw Machines

There are five different types of screw machines. These

include the
❑ single spindle and multiple spindle automatic screw machines,
❑ turret lathe,
❑ CNC screw machine, and
❑ automatic chucker.

❑ When buying screw machines, shoppers should keep in mind

that for any version purchased,
❑ personnel must be trained or hired to operate the
machinery.
❑ Adequate training is a necessity to prevent injury to the
operator and damage to the machine. 156
3.3.1 Types of Screw Machines Contd.

Single spindle automatic screw machine - used for

machining small-to-medium sized parts.

❑ Single spindle automatic screw machines typically

produce components at the slowest rate
❑ compare to other screw machines,
❑ because they operate using a single spindle

❑ They can be found in hand-turned and fully

automated models.
157
3.3.1 Types of Screw Machines Contd.

Multiple spindle automatic screw machine - also

used for
❑ machining small-to-medium sized parts and
❑ comprises the most common screw machine
type available.

❑ Multiple spindle automatic screw machines

❑ could turn out such parts in high volume
❑ due mainly to the increased number of spindles.

❑ They are generally fully automated. 158

3.3.1 Types of Screw Machines Contd.

Turret lathe - like the automatic screw machines,

❑ a turret lathe allows machining of small-to-medium
sized parts,
❑ but also has the added benefits of an indexable tool
holder.

❑ This tool holder allows the machine to automatically

change out tool bits.

❑ This, in turn,
❑ speeds up the machining operation and
❑ decreases the amount of tool bits change out. 159
3.3.1 Types of Screw Machines Contd.

CNC screw machine - is similar to the automatic

screw machines
❑ with added benefits of computer control.

❑ This typically involves entering a program that the

machine then follows,
❑ which allows the machine to be run a single
operator.

❑ All CNC screw machines are fully automated.

160
3.3.1 Types of Screw Machines Contd.

Automatic chucker - is similar to an automatic

screw machine.

❑ The main difference is that the automatic

chuckers handle large-sized parts.

❑ These types of machines are

❑ becoming obsolete with the introduction of
more advanced CNC machines.
161
3.3.2 Functional Parts of a Screw Machine

Despite the numerous components of an automatic

screw machine,
❑ they all work together to produce precise parts
repeatedly.

❑ Functional parts of a screw machines are the

❑ headstock, feed screw, carriage and spindle among
others.

Headstock - which holds the main spindle,

❑ is a solid piece of component that keeps the cutting
operation as steady and accurate as possible. 162
3.3.2 Functional Parts of a Screw Machine Contd.

❑ The main spindle is a hollow piece on the headstock,

❑ permitting the machined workpiece to extend into
the work area
❑ in order to reduce preparation time and save on raw
material.

Feed screw - is the driveshaft, which gives the carriage

mechanism its power by driving the gears controlling it.

❑ The feed screw works along with the lead screw to drive
the spindle,
❑ which in turn spins the machined workpiece. 163
3.3.2 Functional Parts of a Screw Machine

Carriage - holds the tool bit and moves it along a

longitudinal or perpendicular facing.

❑ This can be carried out by the operator through the use

of a hand wheel or by engaging the feed shaft,
❑ which engages the tool bit mechanism and runs it
automatically.

❑ In newer models, the operator inputs the programming

into a CNC machine,
❑ which then directs the tool bit according to the
programming. 164
3.3.2 Functional Parts of a Screw Machine

Spindle - holds the workpiece, and as it spins the

different tool bits in contact with the workpiece,
❑ machining of unneeded material is carried
out.

❑ Typically, in the past, machine screws have only a

single spindle.

❑ Modern screw machines, in particular, the CNC

screw machines, feature multiple spindles.
165
3.3.3 Different Operations of a Screw Machine

Screw machines are used to

❑ manufacture small parts and components.

❑ Though, they are called screw machines,

❑ screws are not commonly produced using
them.

Common operations of a screw machine are the

❑ complex shape, threading, and rotary broaching
among others.
166
3.4 Fabrication Technology

❑ Fabrication involves the construction of structures, machines and

components
❑ by various manufacturing processes using different raw materials.

❑ Metal fabrication is the building of metal structures, machines or metal

parts
❑ by cutting, forming, joining and assembling processes.

❑ There are three basic stages involved in the fabrication of structures,

machines or components, which usually begins with the
❑ graphic design, i.e. engineering drawings of the component or
machine to be fabricated;
❑ actual fabrication processes and assembling, and
❑ installation and testing of the final project.
167
3.4 Fabrication Technology Contd.

❑ The actual fabrication process involves five main stages,

❑ planning, measuring, marking out and production of templates,
❑ cutting and preparation of blanks from stock material,
❑ forming of blanks to make the required component or part,
❑ joining and assembly, and
❑ finishing operations.

❑ The planning, measuring and marking out are performed in strict

compliance with the engineering graphics design.
❑ After the measuring and marking out, the cutting operation follows.
❑ Cutting is achieved by shearing, sawing or turning using machine
tools such as jigsaw, computer numerical control (CNC) machine and
water jet among others.
168
3.4 Fabrication Technology Contd.

❑ The next stage after the cutting operations is the forming

operation.

❑ Forming involves bending and shaping of the component using

appropriate hand and machine tools.

❑ After the forming operation is completed, the next stage is the

assembling of various components or parts.

❑ The assembling process involves joining of pieces together

❑ by welding, riveting, threaded fasteners, etc.

❑ The final stage is the finishing operation, which involves

machining, painting, etc. 169
4. Summary

❑ Machine tools are any of a class of power-driven devices designed for carrying out specific
machining operations in order to produce a desired size, shape and surface finish of workpiece
being machined.

❑ The productivity of a machine tool is measured either by the number of parts produced in a
unit of time, volumetric removal rate, or specific removal rate per unit of power consumed.

❑ Machine tools, according to their specialisation can be divided into general-purpose (universal
or standard), special-purpose, and limited-purpose machines.
❑ main functions of machine tools are for
❑ holding the workpiece to be machined, holding the tool, and achieving the required
relative motion to generate the required workpiece geometry.

❑ Examples of machine tools are the

❑ lathes, which are any of a class of machine tools that cuts and shapes materials by revolving
the workpiece against a cutting tool;
❑ milling machines, which are any of a class of machine tools that removes material as the
workpiece is fed against a rotating multipoint cutter;
❑ screw machines, shaping machines, grinding machines, drilling machines, etc.
170
4. Summary Contd.

❑ The operations performed using a lathe are either by

❑ holding the workpiece between centres or by a chuck, e.g. straight turning,
shoulder turning, taper turning, chamfering, thread cutting, etc.; and
❑ operations performed by holding the work by a chuck, faceplate or angle plate,
e.g. undercutting, parting-off, internal thread cutting, drilling, reaming, etc.
❑ The two distinct methods of milling operations using a milling machine are
❑ classified as the up-milling and down milling operations.
❑ Different kinds of milling operations performed on a milling machine are the
❑ plain (slab), face, side, angular, gang milling operations, etc.

❑ Metal fabrication is the building of metal structures, machines or metal parts by

cutting, forming, joining and assembling processes.
❑ There are three basic stages involved in the fabrication of structures, machines or
components, which usually begins with the
❑ graphic design, i.e. engineering drawings of the component or machine to be
fabricated;
❑ actual fabrication processes and assembling, and
❑ installation and testing of the final project. 171
Unit 4: Use of Hand Tools

❑ Contents Outline
1. Introduction
2. Objectives
3. Main Content
3.1 Measuring and Marking Tools
3.1.1 Vernier Calipers
3.1.2 Calipers
3.1.3 Micrometer
3.1.4 Scriber and Surface Gauges
3.1.5 Try Squares
3.1.6 Spring Dividers
3.1.7 Centre and Dot Punches
3.1.8 Surface Plates
3.2 Work Holding and Supporting Tools
3.2.1 Workbenches
3.2.2 Bench Vices
3.2.3 Vee Blocks
3.2.4 C-Clamps
3.2.5 Angle plate 172
Contents Outline Contd.

3.3 Cutting Tools

3.3.1 Hacksaws
3.3.2 Chisels
3.3.3 Twist Drills
3.3.4 Taps and Dies
3.4 Finishing Tools
3.4.1 Reamers
3.4.2 Files
3.5 Miscellaneous Tools
3.5.1 Hammers
3.5.2 Wrenches
3.5.3 Screwdrivers
3.5.4 Crowbars
4. Summary 173
1. Introduction

Tools refer to any device or instrument, especially

one held in the hand, used to carry out a particular
function.

❑ It ranges from the simple hand tools, such as a

file, to the very complex machine tools, such as a
computer numerical control (CNC) machine.

❑ Hand tools are tools that are manually controlled.

❑ Examples are the screwdrivers, spanners,
pliers, hammers, wrenches, Allen keys, etc.
174
1. Introduction Contd.

There are different types of hand tools used in the

workshop.

❑ These hand tools can be classified into five

categories based on their operations and usage,
which are the

❑ measuring and marking, holding and

s u p p o r t i n g , c u t t i n g , f i n i s h i n g , a n d
miscellaneous tools.
175
3.1 Measuring and Marking Tools

Measuring and marking out are the preliminary

work
❑ for providing outlines and centres, given the
detailed dimension of required shapes and
their parts geometry.

❑ The desired parts could, then be cut or machined

to the required shape and size.

❑ Some of these tools perform specialised function

while others perform a common function. 176
3.1 Measuring and Marking Tools Contd.

The commonly used measuring and marking tools are

❑ Vernier caliper - a linear measuring tool,

❑ used to measure accurately the outer dimensions of round,
flat, and square components as well as the inner size of holes
and bores.

❑ It has a narrow blade, usually made of stainless steel, used as

a depth gauge for measuring the depth of bar slots, keyways,
etc.

❑ The vernier caliper has two jaws - the external jaws, located at
one end of its main scale and the internal jaws, which is made as
part of a vernier scale. 177
3.1 Measuring and Marking Tools Contd.

❑ Besides, both pair of measuring jaws, the depth gauge

has the main features including main and vernier
scales.
❑ The reading accuracy in metric system is 0.02 mm.

❑ It takes a little practice to read a vernier caliper

properly. The caliper often has a dial or digital
readouts.
❑ To read a vernier caliper, read the large number
division first, followed by the small number division,
and the number of smaller subdivisions.
178
3.1 Measuring and Marking Tools Contd.

❑ Each represents 0.635 mm to be added to the

measurement.
❑ Afterwards, read which line on the vernier lines
up with a line on the main scale. For each line, a
thousandth must be added to the measurement.

Figure 4.1: Schematic illustration of a vernier caliper, showing its

essential features
179
3.1 Measuring and Marking Tools Contd.

Caliper - a very simple tool that could be as

simple as a compass with inward or outward-
facing points.
❑ used to measure the distance between two
symmetrically opposing sides

To take measurement with a caliper, its tips are

adjusted to fit across the points to be measured.
❑ The caliper is then removed and the distance
between its tips together with a measuring
tool, such as a ruler or steel rule is taken 180
3.1 Measuring and Marking Tools Contd.

❑ In the hands of a skilled user, the caliper could

achieve +/- 0.05 mm accuracy

❑ There are two types of calipers, which are

❑ Outside calipers, used to measure external
dimensions such as length, external diameter
of holes and thickness of a bar; and

❑ Inside calipers, used to measure internal

dimensions such as internal diameter of
holes, width of slot or grooves, etc. 181
3.1 Measuring and Marking Tools Contd.

(a) Outside caliper (b) Inside caliper

Figure 4.2: Schematic illustrations of different types of caliper,
showing the outside caliper in (a) and inside caliper in (b)

182
3.1 Measuring and Marking Tools Contd.

Micrometer, also called micrometer screw gauge

- an instrument that incorporates a calibrated
screw, widely used for

❑ components precision measurement in

engineering and machining, and

❑ measuring small distances or thicknesses

between its two faces among others.
183
3.1 Measuring and Marking Tools Contd.

❑ Generally, it provides greater precision than a

caliper, and could measure a smaller range of
lengths.

❑ In the hands of a skilled user, the micrometer is the

most accurate among the available hand-held tool.

❑ When precision measurements are needed, the

micrometer is the ideal tool for the job
❑ because the dimension and reading are on the
same axis, supported by a strong frame at the
anvil end. 184
3.1 Measuring and Marking Tools Contd.

❑ To use a micrometer, place the part in the

opening. Afterwards, turn the thimble until the
spindle contacts the work.

❑ To apply a consistent pressure to the part, use the

ratchet stop and the clamp ring to hold the
thimble in place while you read the micrometer.

❑ To read the micrometer, read the exposed number

on the sleeve or barrel (with main scale), followed
by the number of divisions past the number.
185
3.1 Measuring and Marking Tools Contd.

❑ The common basic types of micrometers based on

their mode of applications are

❑ Outside micrometers also known as micrometer

calipers - usually used to measure the external
diameter;

❑ Inside micrometers - used to measure the diameter of

holes; and

❑ Depth micrometers - used to measure the depths of

slots and steps. 186
3.1 Measuring and Marking Tools Contd.

(a) Outside micrometer

(b) Inside micrometer

(c) Depth micrometer

Figure 4.3: Pictorial illustrations of the types of micrometers, indicating their essential features,
showing the outside micrometer in (a), inside micrometer in (b) and depth micrometer in (c) 187
3.1 Measuring and Marking Tools Contd.

Scriber - a slender hardened and tempered high carbon steel tool,

tempered to a suitable hardness at its front edge and its tip is
0
generally ground to about 12 to 15
❑ used for scribing or marking lines onto the surface of a workpiece, or
❑ for locating the centres of round bars.

Surface gauge - comprises a cast iron base on the centre in which a

steel rod is fixed vertically.

(a) Scriber (b) Surface gauge

Figure 4.4: Schematic illustrations of a scriber in (a) and surface gauge in (b), showing
their essential features 188
3.1 Measuring and Marking Tools Contd.

The try square, otherwise known as engineer’s

square - a blade made up of hardened tool steel,
attached to a base at 900.
❑ The base is made up of cast iron or steel.

Try squares are used for

❑ marking out right angles,
❑ measuring straightness of surfaces, and
❑ used during work inspection, for checking
squareness and straightness of two surfaces. 189
3.1 Measuring and Marking Tools Contd.

Figure 4.5: Pictorial illustrations of typical try squares

Spring dividers - a tool made up of hardened steel,

which is basically similar to the calipers except that
its legs are kept straight and pointed at the
measuring edge.
❑ The legs are used for
❑ scribing arcs or circles onto a workpiece, and
❑ laying out perpendicular lines, by setting lines. 190
3.1 Measuring and Marking Tools Contd.

Figure 4.6: Pictorial illustration of a typical spring divider

Punch - is basically made up of high carbon steel,

which has a cylindrical knurled body with some plain
length at the top and made pointed at the other end.
❑ Punches are used for
❑ making indentations on the scribed lines, in
order to make them more visible. 191
3.1 Measuring and Marking Tools Contd.

A punch is specified by its length and diameter.

❑ There are two types of punches, which are the dot

and centre punches. A dot punch has a point angle
of either 30 or 600,
❑ used for marking small dots on the reference
line

❑ While a centre punch has a point angle of 900,

❑ used for making a large indent on a workpiece
for drilling operation. Both punches are made
of hardened tool steel. 192
3.1 Measuring and Marking Tools Contd.

(a) Dot punch (b) Centre punch

Figure 4.7: Pictorial illustrations of the punches, showing the dot punch in (a)
and centre punch in (b)

Surface plate - a tool made up of malleable cast iron or

graphite, machined and scraped to a high degree of
flatness,
❑ which is specified by length, width, height and grade.

❑ The degree of finishing of the surface plate depends upon

whether it would be used for
❑ bench work in a fitting shop or
❑ inspection in quality control. 193
3.1 Measuring and Marking Tools Contd.

❑ The flat surface is used as a datum surface

measuring and marking out purposes.

❑ Large surface plate that can stand on the floor

is known as surface table,
❑ used for testing the flatness and trueness of
surfaces.

Figure 4.8: Pictorial illustration of a surface plate 194

3.2 Work Holding and Supporting Tools

Work holding (or clamping) and supporting tools

are devices for
❑ keeping workpiece in firm position during
work operations in the workshop.

❑ They are usually located on workbench to ensure

proper firmness and rigidity during operations.

❑ The commonly used work holding and supporting

tools are the
❑ workbenches, bench vices, vee blocks, c-
clamps and angle plates among others. 195
3.2 Work Holding and Supporting Tools Contd.

Workbench - is a strong, heavy and rigid table like-

structure, which is made of hard wood or metal,
❑ usually situated in the workshop, in particular, for
fitting operation.

❑ A fitting process can be done at various places, but most

of the important operations of fitting are generally
carried out on a table called workbench.

Figure 4.9: Pictorial illustration of a typical workbench 196

3.2 Work Holding and Supporting Tools Contd.

Bench vice - a mechanical device, made of a cast iron

body and jaws
❑ for holding workpiece during working operation in
the workshop.

❑ The jaw comprises two main parts, the

❑ stationary (or fixed) and sliding (or movable) jaws,
❑ which are both fitted with jaw plates.

❑ The stationary jaw is fixed to the body while the

sliding jaw slides on a square threaded screw
❑ with the help of a handle. 197
3.2 Work Holding and Supporting Tools Contd.

Figure 4.10: Pictorial illustration of a bench vice, showing its essential parts

Vee block - is a work holding device where v-grooves are

provided to hold and support round objects longitudinally.

❑ With a clamp, the vee block is generally used to

❑ hold circular workpiece for marking out or machining.
198
3.2 Work Holding and Supporting Tools Contd.

Figure 4.11: Pictorial illustration of a vee block attached with clamp

❑ C-clamp - a device used for holding workpiece against

an angle plate, v-block or any other surface,
❑ when gripping is required.

❑ For instance, c-clamp is used for holding planks after

gluing, most in particular, in wood workshop. 199
3.2 Work Holding and Supporting Tools Contd.

❑ Its fixed jaw is shaped like the English alphabet ‘C’

or ‘G’,
❑ with a round shaped movable jaw, which is
directly fitted to the threaded screw at the end.

Figure 4.12: Pictorial illustration of a c-clamp with alternative

wingnut 200
3.2 Work Holding and Supporting Tools Contd.

Angle plate - a tool made of cast iron in different sizes and

ground to a high degree of accuracy,
❑which has two planed surfaces at right angles to each
other and
❑various slots on each surface for mounting and holding
workpiece.
❑ Angle plates are used for supporting or setting up work
vertically.

Figure 4.13: Pictorial illustration of a typical angle plate 201

3.3 Cutting Tools

Cutting tools in engineering workshop range

from

❑ hand held cutting tools to cutting tools

employed in sophisticated machine tools.

❑ However, the commonly used hand cutting

tools are the

❑ hacksaws, chisels, twist drills, and taps and

dies among others. 202
3.3 Cutting Tools Contd.

Hacksaw - a saw with a narrow fine-toothed blade set in a

frame, used in particular, for cutting metal.

❑ It consists of a
❑ frame, made of mild steel and
❑ a blade, made of high carbon steel or high-speed steel,
❑ which is set in the frame and tightened with the help
of a flange nut.

❑ There are two types of frame, namely the

❑ fixed type, which only takes one length of blade, and
❑ the adjustable type, which could take different blade
lengths. 203
3.3 Cutting Tools Contd.

❑ The blades can be classified as

❑ forward or backward cut,
❑ depending upon the direction of cut.

❑ The teeth of the blades are generally forward cut such that,
❑ the pressure is applied in the forward direction only while the
backward direction is idle.

Figure 4.14: Pictorial illustration of a typical hacksaw, indicating its essential

features 204
3.3 Cutting Tools Contd.

❑ Chisel - a long-bladed hard steel cutting tool with a

bevelled cutting edge and a handle,
❑ which is struck with a hammer or mallet when used
to cut or shape wood, stone or metal.

❑ It is used for
❑ removing surplus metal,
❑ cutting thin sheets or chipping any material softer
than the chisel itself.

❑ It can also be used in restricted areas for

❑ such work as shearing rivets, splitting seized or
damaged nuts from bolts. 205
3.3 Cutting Tools Contd.

Figure 4.15: Schematic illustration of a chisel, indicating its cutting edge geometry

Twist drill - a pointed tool that is rotated to cut holes in a material.

❑ It is made of a cylindrical hardened steel bar
❑having spiral flutes (grooves) running throughout the length of the body,
and
❑a conical point with cutting edges formed by the ends of the flutes.

❑ Flutes are incorporated to carry away the chips of metal and the outside
surface
❑is relieved to produce a cutting edge along the leading side of each flute. 206
3.3 Cutting Tools Contd.

❑ Twist drills have from one to four spiral flutes.

❑ Drills with two flutes are used

❑ for most drilling while those with three or four
flutes are used principally to follow smaller drills
or to enlarge holes.

❑ The principal parts of the twist drill are the

❑ shank, body and heel.

❑ The drill shank is the end that fits into the chuck of a
hand or power drill. 207
3.3 Cutting Tools Contd.

❑ The two shank shapes most commonly used in hand

drills are the
❑straight shank and square or bit stock shank.
❑ The tapered shanks are generally used in drill presses.

Figure 4.16: Pictorial illustration of a twist drill, indicating its essential cutting
edge features 208
3.3 Cutting Tools Contd.

Taps and dies - are made of hard tempered steel,

❑which are ground to an exact size.

❑ A tap is a cutting tool used for

❑ cutting internal threaded holes in a material
❑ while a die is a cutting tool used for
❑cutting external threads on round stock.

❑ The process of producing the internal thread

❑ by taps is known as tapping.

❑ The hand taps are typically supplied in sets of three taps for
each diameter and thread series to cut any particular size. 209
3.3 Cutting Tools Contd.

❑ Each set consists of a

❑ taper or first tap, intermediate, second, or plug tap and
bottoming tap.
❑ These taps in a set are identical in diameter and cross section,
which differ only in their amount of taper.

(a) Taper

(b) Plug

(c) Bottoming
Figure 4.17: Pictorial illustrations of hand taps, showing the taper in (a), plug in (b) and
bottoming in (c) 210
3.3 Cutting Tools Contd.

❑ Dies may be classified as

❑ adjustable round split die and
❑ plain round split die.

❑ The adjustable split die has an adjusting screw

❑ that can be tightened so that the die is spread
slightly.

❑ By adjusting the die, its diameter and fit of the thread

can be controlled.
❑ Plain dies are not adjustable, making it difficult to
perform variety of thread with this type of die. 211
3.3 Cutting Tools Contd.

(a) Adjustable round split die

(b) Plain round split die

Figure 4.18: Pictorial illustrations of the different types of dies, showing the
adjustable round split die in (a) and plain round split die in (b)

There are many types of wrenches for turning taps and dies.
❑ These include the T-handle and adjustable tap wrenches, and
❑ diestock for round split dies, are a few of the more common
types. 212
3.3 Cutting Tools Contd.

❑ Dies are fixed in a diestock (die holder),

❑ which comprises a holder for the die, turned
using the long handles.

Figure 4.19: Schematic illustrations of tap wrenches and

diestock 213
3.4 Finishing Tools

❑ There are a number of finishing tools for

carrying out finishing operations.

❑ Some of these tools perform

❑ specialised function while others perform a
common function.

❑ The commonly used finishing tools are the

reamers, files, etc.
214
3.4 Finishing Tools Contd.

Reamer - a tool for widening or finishing drilled holes.

❑Reaming is an operation of sizing, widening or finishing
drilled holes,
❑with the help of a cutting tool called reamer, having a
number of cutting edges.

❑ For this operation, a hole is first drilled, in which its size is

slightly smaller than the desire finished size and then a hand
or machine reamer is used for finishing the hole to the
correct size.

❑ Hand reamer is operated by hand, with a tap wrench fitted

on the square end of the reamer and with the workpiece
held in a vice. 215
3.4 Finishing Tools Contd.

❑ Reamers are used to smooth and enlarge holes to

exact size.

❑ Holes produced by drilling are seldom accurate in

size and usually have rough surfaces.
❑ A reamer is also used to finish already drilled holes
to exact size with smoothened surface.

Square Shank Neck Flute Chamfer

Figure 4.20: Pictorial illustration of a hand reamer, showing its
main features 216
3.4 Finishing Tools Contd.

File - a multi-point cutting tool, which is used to put

finishing touches on a machined workpiece.

❑ Filing is one of the methods of removing small

amounts of material from the surface of a metal part.

❑ Files are made of hardened steel, having small

parallel rows of cutting edges or teeth on its surfaces.

❑ They are manufactured in variety of shapes and sizes

with different degree of coarseness.
217
3.4 Finishing Tools Contd.

❑ Files are used to

❑ square ends, file rounded corners, remove
burrs and slivers from metal, and straighten
uneven edges, filing of holes and slots, and
smooth rough edges.

Figure 4.21: Pictorial illustration of a typical workshop file,

indicating its main features
218
3.4 Finishing Tools Contd.

❑ Files can be classified according to the number of cuts on its

surface. These include the

❑Single cut files, whose teeth are cut in a parallel row at

an angle of 60° to the face,

❑ Double cut files, which have another row of teeth,

added in an opposite direction to the single cuts.
Material removal is more when using double cut files,
and

❑Rasp cuts files, which are generally used on wood, PVC

and rubber materials. They possess very coarse teeth
and usually used on soft material. 219
3.5 Miscellaneous Tools

❑ Miscellaneous tools are regarded as general-purpose tools that are

commonly found in engineering workshop.
❑ These include the hammers, screwdrivers, set of spanners,
wrenches, pliers and crowbars among others.

Hammer - a striking tool with a heavy soft or hard head, mounted

at right angles at the end of a handle, used for jobs such as driving
in nails.

❑ The striking head can be made of soft or hard materials depending

on the usage.

❑ Hammers are classified as either hard or soft.

❑ Hard hammers have steel heads such as blacksmith types or
mauls made for heavy hammering. 220
3.5 Miscellaneous Tools Contd.

❑ The ball peen hammer is the commonest hammer, used

by the machinists.
❑ It has a rounded surface on one end of the head,
❑ which is used for upsetting or riveting metal, and
❑ a hardened striking surface on the other.

❑ Two other workshop hammers are the

❑ straight peen and cross peen hammers.

❑ Softheaded hammers, usually made of wood, brass, lead,

rawhide, hard rubber or plastic striking surface,
❑ are used to strike workpiece that could be damaged
with hard hammers. 221
3.5 Miscellaneous Tools Contd.

❑ used in forming soft metals and striking surfaces

that are considered fragile.

❑ Soft-faced hammers should not be used for

❑ striking punch heads, bolts, or nails, as using
one in this fashion will quickly ruin this type of
hammer.

❑ A mallet is a hammer-like tool with a large head

typical made of hickory, rawhide, or rubber.
❑ handy for shaping thin metal parts without
causing dents with abrupt corners. 222
3.5 Miscellaneous Tools Contd.

(a) Maul

(b) Ball peen hammer (c) Straight peen hammer

(d) Cross peen hammer (e) Mallet

Figure 4.22: Pictorial illustrations of different kinds of hammer,
showing the maul hammer in (a), ball peen hammer in (b), straight
peen hammer in (c), cross peen hammer in (d) and mallet in (e) 223
3.5 Miscellaneous Tools Contd.

Wrench - a multi-purpose hand tool for turning cap

screws, bolts and nuts.
❑ Chrome-vanadium steel is the most widely used metal
for making wrenches, which made them, almost
unbreakable.

❑Generally classified as open-end, box-end, socket,

adjustable, ratchet and special wrenches.

❑ Open-end wrench is best suited for square-headed bolts,

and usually fit two different sizes, one on each end.
❑ The ends of this type of wrench are angled so they can
be used in close quarters. 224
3.5 Miscellaneous Tools Contd.

❑ Box-end wrench has double ended boxes and also offset to clear the
user’s hand.

❑ The boxes completely surrounds the nut or bolt and usually has 12
points so that the wrench can be reset after rotating only a partial
turn.

❑ Mostly used on hex-headed bolts, these wrenches have the

advantage of precise fit.

❑ Socket wrenches are similar to the box wrenches because they also
surround the bolt or nut and are usually made with 12 points,
contacting the six-sided bolt or nut.

❑ used with socket head cap screws and socket setscrews, and are
made detachable from various types of drive handles. 225
3.5 Miscellaneous Tools Contd.

❑ The adjustable wrench is a handy utility tool

that has smooth jaws and
❑ is designed as an open-end wrench.

❑ It has a fixed jaw and the movable jaw,

❑ s l i d e s by a t h u m bs c rew o r s p i ra l
screwworm adjustment on the wrench
handle.

❑ One adjustable wrench does the work of

several open-end wrenches. 226
3.5 Miscellaneous Tools Contd.

(a) Open-end wrench

(b) Box-end wrench

(c) Set of socket wrenches

(d) Adjustable wrenches

Figure 4.23: Pictorial illustrations of different types of wrenches, showing
the open-end wrench in (a), box-end wrench in (b), socket-end wrench in
(c) and adjustable wrenches in (d) 227
3.5 Miscellaneous Tools Contd.

Screwdriver - a hand tool used for tightening and

loosening screws or screw head bolts.
❑ Screwdrivers can be classified by their shape, type of
blade, and blade length.

❑ It is important to use the right width blade when

installing or removing screws.

❑ The two types of recessed head screws in common

use are the
❑ Phillips, and
❑ Reed and Prince. 228
3.5 Miscellaneous Tools Contd.

(a) Flat head screwdriver

Philips Reed and Prince

(b) Screwdriver blade shapes
Figure 4.24: Pictorial illustration of a screwdriver, showing the flat head
screwdriver in (a) and screwdriver blade shapes in (b) 229
3.5 Miscellaneous Tools Contd.

Crowbar - a tool consisting of a metal bar with a single

curved end and flattened points,
❑ often with a small fissure on one or both ends.

❑ Crowbars are used as a lever either to force apart two

objects or remove nails.

❑ Crowbars are commonly used to open nailed wooden

crates, remove nails or pry apart boards.

❑ Crowbars can be used as any of the three lever classes

❑ but the curved end is usually used as a first-class
lever, and the flat end as a second-class lever. 230
3.5 Miscellaneous Tools Contd.

Figure 4.25: Pictorial illustration of a crowbar

4. Summary
❑ Tool refers to any device or instrument, especially one held in the hand,
which is used to carry out a particular function, like the production of a
product or any related activities.
❑Hand tools are tools that are manually controlled.

❑ Hand tools can be classified into

❑measuring and marking, holding and supporting,
❑ cutting, finishing, and miscellaneous tools based on their operations
and usage. 231
Unit 5: Engineering Approach to Design

Engineering approach to design is the core of engineering,

❑which can simply be expressed as the processes involve in
engineering design and fabrication. These include

❑Problem identification, which could be from customers, personal

intuition, careful observation etc.;
❑Conceptual design - ideas, sketches and solution listing;
❑Refinement - computer modelling, data base development;
❑Testing - analysis and simulation of all design aspects;
❑Prototyping - visualising and improving the design;
❑Communication - through engineering drawings, specifications; and
❑Production - final design, manufacturing, distribution.

Students’ Term Paper/ Group Project:

❑Write a short essay with at least 1,500 words and not more than 2,500
words on the topic titled Engineering Approach to Design. 232
Thank
you

for

your
audience
233