The Influence Of Machining Parameters On Tool Wear And Surface Finish.

THE INFLUENCE OF MACHINING PARAMETERS ON

TOOL WEAR AND SURFACE FINISH

NOR HARIYANI BINTI ABD WAHAB

B050810303

UNIVERSITI TEKNIKAL MALAYSIA MELAKA 2011

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

THE INFLUENCE OF MACHINING PARAMETERS ON TOOL

WEAR AND SURFACE FINISH

This report submitted in accordance with requirement of the Universiti Teknikal Malaysia Melaka (UTeM) for the Bachelor Degree of Manufacturing Engineering

(Manufacturing Process)

by

NOR HARIYANI BINTI ABD WAHAB B050810303

UNIVERSITI TEKNIKAL MALAYSIA MELAKA

BORANG PENGESAHAN STATUS LAPORAN PROJEK SARJANA MUDA

TAJUK: The Influence of Machining Parameters on Tool Wear and Surface Finish SESI PENGAJIAN: 2010/11 Semester 2

Saya NOR HARIYANI BINTI ABD WAHAB

mengaku membenarkan Laporan PSM ini disimpan di Perpustakaan Universiti Teknikal Malaysia Melaka (UTeM) dengan syarat-syarat kegunaan seperti berikut: 1. Laporan PSM adalah hak milik Universiti Teknikal Malaysia Melaka dan penulis. 2. Perpustakaan Universiti Teknikal Malaysia Melaka dibenarkan membuat salinan

untuk tujuan pengajian sahaja dengan izin penulis.

3. Perpustakaan dibenarkan membuat salinan laporan PSM ini sebagai bahan pertukaran antara institusi pengajian tinggi.

4. **Sila tandakan (√)

SULIT

TERHAD

TIDAK TERHAD

(Mengandungi maklumat yang berdarjah keselamatan atau kepentingan Malaysia yang termaktub di dalam AKTA RAHSIA RASMI 1972)

(Mengandungi maklumat TERHAD yang telah ditentukan oleh organisasi/badan di mana penyelidikan dijalankan)

Alamat Tetap:

1201,Kampung Pasir Panjang 21100, Kuala Terengganu.

Tarikh: _________________________

Disahkan oleh:

PENYELIA PSM

Tarikh: _______________________

** Jika Laporan PSM ini SULIT atau TERHAD, sila lampirkan surat daripada pihak berkuasa/organisasi berkenaan dengan menyatakan sekali sebab dan tempoh laporan PSM ini perlu dikelaskan sebagai SULIT atau TERHAD.

DECLARATION

I hereby declare that this report entitled “THE INFLUENCE OF MACHINING PARAMETERS ON TOOL WEAR AND SURFACE FINISH” is the result of my own research except as cited in the references.

Signature : ... Author’s Name : ... Date : ...

APPROVAL

This report is submitted to the Faculty of Manufacturing Engineering of UTeM as a partial fulfillment of the requirements for the degree of Bachelor of Manufacturing Engineering (Engineering Process). The member of the supervisory committee is as follow:

………. Supervisor

ABSTRAK

Proses melarik adalah proses memesin ke atas permukaan bahan kerja dengan menghasilkan tatar(chips). Dalam proses larik, kehausan mata alat dan kekasaran permukaan dipengaruhi oleh beberapa parameter seperti kelajuan pemotongan, kedalaman pemotongan, kadar suapan dan juga ciri-ciri mesin. Tujuan utama kajian ini adalah untuk mengkaji parameter-parameter mesin yang mempengaruhi ke atas kehausan mata alat dan kekasaran permukaan. Dalam kajian ini ‘Tungsten carbide’ digunakan sebagai alat pemotongan untuk memesin bahan kerja (mild steel). Kaedah ‘Design Of Experiment (DOE)’ digunakan untuk mengkaji hubungan di antara pelbagai proses parameter (kedalaman pemotongan, kelajuan pemotongan, dan kadar suapan) dengan kehausan mata alat dan kekasaran permukaan. Kehausan mata alat(Flank wear) diukur dengan menggunakan ‘Scanning Electron Microscope’ dan kekasaran permukaan diukur dengan munggunakan ‘Portable Profilometer’. Keputusan kajian ini menunjukkan bahawa kehausan mata alat dipengaruhi oleh kadar suapan dan kelajuan pemotongan manakala kekasaran permukaan dipengaruhi oleh kadar suapan. Keputusan kajian ini juga menunjukkan bahawa terdapat interaksi yang kuat antara kedalaman pemotongan dengan kadar suapan dan juga interaksi antara kedalaman pemotongan dengan kelajuan pemotongan yang mempengaruhi kehausan mata alat. Walaubagaimanapun, tidak ada kesan interaksi yang mempengaruhi kekasaran permukaan.

ABSTRACT

Single point turning is a material removal process from the surface of a workpiece by producing chips. In turning, the tool wear and surface roughness are commonly influenced by several parameters such as cutting speed, depth of cut, feed rate and characteristics of the machine tool. The main purpose of this research is to study the influence of machining parameters on tool wear and surface finish. In this reserch tungsten carbide was used as a cutting tool to machine the workpiece (mild steel). Design Of Experiment (DOE) method was applied as the research approach to ascertain the relationship between various process parameters ( depth of cut, cutting speed, and feed rate) and the tool wear and surface roughness. Flank wear was measured using Scanning Electron Microscope(SEM) and surface roughnesswas measured using portable profilometer. The result of this research indicates that the tool wear was influenced by feed rate and cutting speed while the surface roughness was influenced by feed rate. The finding also indicate that there were strong interaction between the depth of cut and feed rate and the interaction between depth of cut and cutting speed that influenced tool wear. However, there is no interaction effect that influenced the surface roughness.

ACKNOWLEDGEMENT

First of all, I am grateful to ALLAH S.W.T for blessing me in finishing my final year project 2, (PSM 2) with success in achieving my objectives to complete this project. Secondly I want to thank my family for giving morale support and encouragement in completing my project and also throughout my study in UTeM as they are my inspiration to success. I also would like to thank my supervisor Dr. Md Nizam Bin Abd Rahman for guiding and supervising my final year project throughout this semester. He has been very helpful to me in finishing my project and I appreciate every advice that he gave me in correcting my mistakes. I would like to apologize to my supervisor for any mistakes and things that I done wrong while doing my project. Thank you very much to all and May god bless you.

DEDICATION

TABLE OF CONTENT

Abstrak i

Abtract ii

Acknowledgemen iii

Dedication iv

Table of Content v

List of Tables viii

List of Figures ix

List Abbreviations xi

1. INTRODUCTION 1

1.1 Background 1

1.2 Problem Statement 3

1.3 Experimental Design 1.3.1 Objectives

1.3.2 Scopes of Study

3 4 4 1.4 Structure of the Report

1.4.1 Chapter 1: Introduction 1.4.2 Chapter 2: Literature Review 1.4.3 Chapter 3: Methodology

1.4.4 Chapter 4: Result and Discussion

1.4.5 Chapter 5: Conclusion and Recommendations

5 5 5 5 5 6

2. LITERATURE REVIEW 7

2.1 Turning Operation 2.2 Cutting Operation

2.2.1 Orthogonal cutting process

7 9 9

2.3 Wear

2.3.1 Wear characterization 2.3.2 Wear mechanisms of tools 2.4 Tool wear mechanism 2.5 Tool wear measurement 2.5.1 Tool life

2.5.2 Tool failure modes 2.5.3 Tool Life Test 2.6 Cutting Tool Materials

14 14 21 25 26 27 28 28 31

2.7 Types of cutting tool 33

2.8 Surface Roughness Measurement 34

2.8.1 Surface Roughness in Turning 2.9 Observations of chip formation

2.10 Turning Process Parameter That Effect the Surface Roughness and Tool Wear

2.11 Single point tools 2.12 Design of Experiment 2.12.1 Full Factorial Experiment

36 38 41 42 43 44

3. METHODOLOGY 46

3.1 Introduction 46

3.2 Flow chart process 47

3.3 Process Flow Chart 48

3.4 Material 49

3.5 Equipment 51

3.5.1 Measurement 52

3.5.2 Clamped workpiece in a chuck 53

3.5.3 Setting lathe machine 53

3.5.4 Centering the tool bit 53

3.5.5 Straight turning 54

3.6 Cutting Parameter 55

3.7 Design of Experiment (D.O.E) 56

3.8.1 Scanning Electron Microscopy Analysis (SEM) 58

3.9 Method to Analyze Surface Roughness 60

3.10 Data Analysis 61

4. RESULT AND DISCUSSION 62

4.1 Introduction 62

4.2 Tool Wear Result 62

4.3 Surface Roughness Result 69

4.4 Design of Experiments

4.4.1 ANOVA Balanced (Tool wear versus Depth of cut, Feed

Rate, Cutting speed)

4.4.2 Pareto Chart of the Standardized Effects 4.4.3 Main Effects Plot for Tool Wear

4.4.4 Interaction Plot for Tool Wear

4.4.5 ANOVA Balanced (Surface roughness versus Depth of cut, Feed rate, Cutting speed)

4.4.6 Pareto Chart of the Standardized Effects 4.4.7 Main Effects Plot for Surface Roughness 4.4.8 Interaction Effects Plot for Surface roughness 4.5 Development of Mathematical Modelling

70 71 72 73 74 75 76 77 78 79

5. CONCLUSION AND RECOMMENDATION 81

5.1 Conclusion 5.2 Recommendations

81 81

REFERENCES 83

APPENDICES

A. Gantt Chart PSM 1 and PSM 2

LIST OF TABLES

Table 2.1 Types of cutting tool wear 16

Table 2.2 Flank wear of variety cutting tool 30

Table 2.3 The General Properties of Cutting Tool Materials 34 Table 2.4 Factors influencing formation of chips 40 Table 2.5 Parameter that Effect Surface Roughness and Tool

Wear

41

Table 2.6 2³ Factorial design ‘Standard Order’. 45

Table 3.1 Chemical Composition Specification. 49

Table 3.2 Sumitomo SPGN120308S cutting tool dimensions 50 Table 3.3 General Properties of Tungsten Carbide 50

Table 3.4 Function of Lathe Machine 54

Table 3.5 The Cutting Parameter Range in accordance with ISO 229.

55

Table 3.6 DOE Matrix 57

Table 3.7 Factors and Levels selected for the Experiments 58

Table 4.1 Flank Wear Result. 63

Table 4.2 Result of Surface Roughness 69

Table 4.3 Result for surface roughness and tool wear to analysis

70

Table 4.4 The regression of equation for surface roughness. 79 Table 4.5 The regression of equation for tool wear. 79

LIST OF FIGURES

Figure 1.1 Single lathe turning machine 2

Figure 1.2 Experimental design of lathe process 3

Figure 2.1 Types of cutting such as (a)orthogonal and(b) oblique cutting

8

Figure 2.2 Turning process involves cutting and feed motion

8

Figure 2.3 Illustration of the deformation zones and simulated slip-line fields in orthogonal cutting

10

Figure 2.4 Heat generation 12

Figure 2.5 Orthogonal machining 12

Figure 2.6 Configuration for orthogonal cutting 13

Figure 2.7 A turning tool insert wear pattern 19

Figure 2.8 Schematic of tool wear distribution 20

Figure 2.9 Typical wear patterns of turning tool using carbide insert

20

Figure 2.10 Abrasive wear 21

Figure 2.11 Adhesive Wear 22

Figure 2.12 Wear of large scale plastic deformation 23

Figure 2.13 Wear of fatigue and fracture 24

Figure 2.14 Diffusion wear of the cutting tool 25

Figure 2.15 Conventional tool wear measurement 30

Figure 2.16 Common properties of cutting tool materials 32 Figure 2.17 Cutting speed and feed capability of various

cutting tool materials

33

Figure 2.20 Effect of feed rate and edge preparation on surface roughness (Ra). Workpiece hardness 47 HRC AISI 51200 steel

37

Figure 2.21 Discontinuous Chip 39

Figure 2.22 Continuous Chip 39

Figure 2.23 Continuous Chip with Built-up Edge 40

Figure 2.24 Turning tool geometry showing all angles 42 Figure 2.25 Tool designations for single point cutting tool 43 Figure 2.26 A 2³ two-level, full factorial design; factors X1,

X2, X3.

45

Figure 3.1 Flow chart process 47

Figure 3.2 Process Flow Chart. 48

Figure 3.3 Tungsten carbide cutting tool insert commercially made by Sumitomo

49

Figure 3.4 Single Turning Lathe machine 51

Figure 3.5 A typical lathe machine 51

Figure 3.6 Single Turning Lathe machine the process 52

Figure 3.7 Scanning Electron Microscopy (SEM) 60

Figure 3.8 Portable Surface Roughness Tester: Model Surftest SJ – 301

61

Figure 4.1 ANOVA Balanced (Tool wear versus Depth of cut, Feed rate, Cutting speed)

71

Figure 4.2 Pareto Chart of the Standardized Effects 72

Figure 4.3 Main Effects Plot for Tool Wear 73

Figure 4.4 Interaction Plot for Tool Wear 74

Figure 4.5 ANOVA Balanced (Surface roughness versus Depth of cut, Feed rate, Cutting speed)

75

Figure 4.6 Pareto Chart of the Standardized Effects 76 Figure 4.7 Main Effects Plot for Surface Roughness. 77 Figure 4.8 Interaction Effects Plot for Surface roughness 78

LIST OF ABBREVIATIONS

AA

CLA

- -

Arithmetic Average Centreline Average

ANOVA - Analysis of Variance

ap - Depth of Cut

BUE - Built Up Edge

DOE - Design of Experiment

f - Feed Rate

ISO - International Standard Organisation

Ra - Surface Roughness

TiC - Titanium Caride

VBB - Flank Wear Land

vs - Cutting Speed

CHAPTER 1

INTRODUCTION

1.1 Background

Turning is a material removal process, which create cylindrical parts by removing away unwanted material. The cutting tool feeds into the rotating workpiece and remove away material in the form of small chips to create the desired shape. The process usually applied using turning lathe machine and the majority of turning operation uses the simple single point cutting tool. In turning, the speed and motion of the cutting tool are commonly influence by several parameters such as cutting speed, depth of cut, cutting fluids and characteristics of the machine tool. These parameters are determined for a particular operation based on the workpiece material, tool material, tool size and more (Kalpakjian, 2006).

The material of the tool is chosen based on a number of factors, including the material of the workpiece, cost, and tool life. Tool life is an important characteristic to be considered when selecting a tool, as it greatly influences manufacturing costs. The cutting tools can be made of various materials, which will determine the tool's properties. These properties include the tool's hardness, toughness, and resistance to wear (Dimla et.al., 1998).

The excessive wear on the cutting tool leads to the tool not being able to support the cutting forces, which can result in tool failure. A cutting tool is considered to have become bad through progressive wear if it cannot produces part within required specifications such as dimensional integrity bad of surface finish or combination of these factors.

Wear is loss of material which usually progress continuously. Progressive wear of a tool takes place mainly in two distinct ways which is wear on the rake face by the formation of crater or built up edge resulting from the action of chip flowing along the face and wear on the flank face including often regions adjacent to the major and minor cutting edges and tool nose, where as characteristic land is formed from rubbing action of newly generated workpiece surface (Grzesik, 2008).

The damages of cutting tool are influenced by certain factor such as stress and temperature at tool surfaces which in turn depend on cutting mode such as turning, drilling or milling, cutting condition and also the presence of cutting fluid in the process. In machining, the tool damaged and its rate are very sensitive to changes in cutting operation and cutting conditions. This is very important in order to minimize machining cost. It is not only to find the most suitable tool and work material for the machining operation, but also to predict the tool life. Today, modern cutting tools have progress enormously increasing their cutting speeds and tool life, due to the materials being used and a better understanding of the cutting parameters. Figure 1.1 below shows the Single Lathe Turning Machine (Boothhroyd, 1985).

1.2 Problem Statement

Tool wear and surface finish were studied in this project. In general, the development of new cutting tools is driven by three factors; the constant demand for increased productivity, the advent of difficult to machine materials and growing environmental, health and safety issues. This study focuses on the cutting tool wear, measured using scanning electron microscope and also its effect on workpiece roughness measured using portable profilometer. This project studied the influence of machining parameters on tool wear and workpiece surface finish using full factorial Design of Experiment.

This study is aimed to find out the answer for the following questions:

i. Which machining parameters (depth of cut, cutting speed and feed rate) significantly influence cutting tool wear and workpiece surface roughness? ii. How does the change in machining parameters‟ values effect the cutting tool

wear and surface roughness?

iii. Is there interaction between the process parameters that affect tool wear and workpiece surface roughness?

1.3 Experimental Design

Relationship between input parameter and output response

Figure 1.2: Experimental Design of Lathe Process.

Input Parameter _{Output Parameter}

Tool wear Surface roughness Cutting speed

Feed rate Depth of cut

Figure 1.2 shows that the experimental design approach of to achieve the objectives of this research. The input parameters in the experiment are cutting speed, feed rate and depth of cut. The output responses of the experiment are the tool wear and surface roughness. Full factorial with two levels was adopted as experimental approach.

1.3.1 Objectives

The objectives of this study are:

(a) To identify machining parameters (depth of cut, cutting speed and feed rate) that significantly influence tool wear and workpiece surface roughness.

(b) To ascertain the effect of the change in machining parameter values on the tool wear and workpiece surface roughness.

(c) To determine if there are interactions between the process parameters that significantly affect tool wear and workpiece surface roughness.

1.3.2 Scopes of Study

This research focused the study of tool wear and workpiece surface roughness in the single point turning operation. All the experiments were carried out using conventional turning machine in UTeM‟s machine shop. Mild steel was used as workpiece and tungsten carbide was used as a cutting tool in this study. This study was focused the influenced of machining parameters on tool wear and surface finish.

1.4 Structure of the report

The summary of each chapter was described in the structure of report. The structure of the report includes Chapter 1 until Chapter 5 of the report.

1.4.1 Chapter 1: Introduction

Include the background of the project, problem statement, experimental design, objectives, scope and project management of the whole project.

1.4.2 Chapter 2: Literature Review

Literature review on wear characterization, surface roughness, the explanation single point turning lathe machine is based on its history, classification, application and production processes.

1.4.3 Chapter 3: Methodology

The methodology of the project contains a brief explanation about the preparation of the experiments including the equipment used measurement on tool wear and surface roughness, experimental approach using full factorial Design of Experiment method, and the data analysis using Minitab software.

1.4.4 Chapter 4: Result and Discussion

Analysis the data of the main effects plot for tool wear and surface roughness, interaction plot for tool wear and surface roughness and also pareto chart of the standardized effects or tool wear and surface roughness.

1.4.5 Chapter 5: Conclusion and Recommendations

The conclusion for a whole of the project and the suggestion for future work not only used for the extension of the project but also share the relevant information to others.

CHAPTER 2

LITERATURE REVIEW

2.1 Turning Operation

Machining is one of the most versatile processes in the manufacturing industry for processing, shaping or cutting various types of work piece materials. Machining is defined as a material removal process that is applied to a workpiece in order to get the required shape. Variety shapes can be produced by machining (Kalpakjian et.al., 2006). Currently there is a lot of emphasize given to develop the machining capabilities in order to achieve near net shapes and also to reduce cost of the machining method, tools and equipments. In the metal cutting process unwanted material is removed from a workpiece in the form of chips for producing finished parts of required dimensions and accuracy. Metal cutting is a highly non-linear and coupled thermo mechanical process, where the mechanical work is converted into heat through the plastic deformation involved during chip formation and also due to frictional work between the tool, chip and workpiece (Chandrakanth, 2000).

Machining operation can be divided into two groups, which is orthogonal and oblique cutting (Edward et.al., 2000). In orthogonal cutting, the relative velocity of the work and the tool is perpendicular to the cutting edge. In oblique cutting, the relative velocity of the work and the tool is not perpendicular to the cutting edge. Majority of cutting operation are oblique cutting. Figure 2.1 shows the differences between orthogonal and oblique cutting.

(a) Orthogonal cutting (b) Oblique cutting

Figure 2.1:Types of cutting (a) orthogonal and (b) oblique cutting (Ghosh et.al., 1986).

Turning is a very basic operation and generally produces cylindrical surfaces. The machine tool used for this type of operation is known as a lathe (Ghosh et.al., 1986). Turning is also one of the most commonly employed operations in experimental work and metal cutting (Edward et.al., 2000). The tool is held rigidly in a tool post and moved at a constant rate along the axis of the bar, cutting away a layer metal to form a surface or more complex profile as the part is being rotated. Turning is also used to as a secondary process to produce better surface finish after being processed by primary processes such as casting, forging, extrusion or drawing process. Figure 2.2 shows the turning process.

1.2 Problem Statement

Tool wear and surface finish were studied in this project. In general, the development of new cutting tools is driven by three factors; the constant demand for increased productivity, the advent of difficult to machine materials and growing environmental, health and safety issues. This study focuses on the cutting tool wear, measured using scanning electron microscope and also its effect on workpiece roughness measured using portable profilometer. This project studied the influence of machining parameters on tool wear and workpiece surface finish using full factorial Design of Experiment.

This study is aimed to find out the answer for the following questions:

i. Which machining parameters (depth of cut, cutting speed and feed rate) significantly influence cutting tool wear and workpiece surface roughness? ii. How does the change in machining parameters‟ values effect the cutting tool

wear and surface roughness?

iii. Is there interaction between the process parameters that affect tool wear and workpiece surface roughness?

1.3 Experimental Design

Relationship between input parameter and output response

Figure 1.2: Experimental Design of Lathe Process.

Input Parameter _{Output Parameter}

Tool wear Surface roughness Cutting speed

Feed rate Depth of cut

Figure 1.2 shows that the experimental design approach of to achieve the objectives of this research. The input parameters in the experiment are cutting speed, feed rate and depth of cut. The output responses of the experiment are the tool wear and surface roughness. Full factorial with two levels was adopted as experimental approach.

1.3.1 Objectives

The objectives of this study are:

(a) To identify machining parameters (depth of cut, cutting speed and feed rate) that significantly influence tool wear and workpiece surface roughness.

(b) To ascertain the effect of the change in machining parameter values on the tool wear and workpiece surface roughness.

(c) To determine if there are interactions between the process parameters that significantly affect tool wear and workpiece surface roughness.

1.3.2 Scopes of Study

This research focused the study of tool wear and workpiece surface roughness in the single point turning operation. All the experiments were carried out using conventional turning machine in UTeM‟s machine shop. Mild steel was used as workpiece and tungsten carbide was used as a cutting tool in this study. This study was focused the influenced of machining parameters on tool wear and surface finish.

1.4 Structure of the report

The summary of each chapter was described in the structure of report. The structure of the report includes Chapter 1 until Chapter 5 of the report.

1.4.1 Chapter 1: Introduction

Include the background of the project, problem statement, experimental design, objectives, scope and project management of the whole project.

1.4.2 Chapter 2: Literature Review

Literature review on wear characterization, surface roughness, the explanation single point turning lathe machine is based on its history, classification, application and production processes.

1.4.3 Chapter 3: Methodology

The methodology of the project contains a brief explanation about the preparation of the experiments including the equipment used measurement on tool wear and surface roughness, experimental approach using full factorial Design of Experiment method, and the data analysis using Minitab software.

1.4.4 Chapter 4: Result and Discussion

Analysis the data of the main effects plot for tool wear and surface roughness, interaction plot for tool wear and surface roughness and also pareto chart of the standardized effects or tool wear and surface roughness.

1.4.5 Chapter 5: Conclusion and Recommendations

The conclusion for a whole of the project and the suggestion for future work not only used for the extension of the project but also share the relevant information to others.

CHAPTER 2

LITERATURE REVIEW

2.1 Turning Operation

Machining is one of the most versatile processes in the manufacturing industry for processing, shaping or cutting various types of work piece materials. Machining is defined as a material removal process that is applied to a workpiece in order to get the required shape. Variety shapes can be produced by machining (Kalpakjian et.al., 2006). Currently there is a lot of emphasize given to develop the machining capabilities in order to achieve near net shapes and also to reduce cost of the machining method, tools and equipments. In the metal cutting process unwanted material is removed from a workpiece in the form of chips for producing finished parts of required dimensions and accuracy. Metal cutting is a highly non-linear and coupled thermo mechanical process, where the mechanical work is converted into heat through the plastic deformation involved during chip formation and also due to frictional work between the tool, chip and workpiece (Chandrakanth, 2000).

Machining operation can be divided into two groups, which is orthogonal and oblique cutting (Edward et.al., 2000). In orthogonal cutting, the relative velocity of the work and the tool is perpendicular to the cutting edge. In oblique cutting, the relative velocity of the work and the tool is not perpendicular to the cutting edge. Majority of cutting operation are oblique cutting. Figure 2.1 shows the differences between orthogonal and oblique cutting.

(a) Orthogonal cutting (b) Oblique cutting

Figure 2.1:Types of cutting (a) orthogonal and (b) oblique cutting (Ghosh et.al., 1986).

Turning is a very basic operation and generally produces cylindrical surfaces. The machine tool used for this type of operation is known as a lathe (Ghosh et.al., 1986). Turning is also one of the most commonly employed operations in experimental work and metal cutting (Edward et.al., 2000). The tool is held rigidly in a tool post and moved at a constant rate along the axis of the bar, cutting away a layer metal to form a surface or more complex profile as the part is being rotated. Turning is also used to as a secondary process to produce better surface finish after being processed by primary processes such as casting, forging, extrusion or drawing process. Figure 2.2 shows the turning process.