Manufacturing design and technology  drills  science and technology of advanced operations

Science and Technology of Advanced Operations “… very valuable knowledge … new procedures to nd the root causes of tool failure with accuracy … based on the innovative concepts … the ri

Science and Technology

of Advanced Operations

“… very valuable knowledge … new procedures to nd the root causes of

tool failure with accuracy … based on the innovative concepts … the right

methodologies and practices to help … selection of the drilling system

components to manufacture high-quality products, improve the efciency

of the drilling process and development of the next generation of

high-performance (HP) drills.”

—J C Outeiro, Arts et Metiers ParisTech

“… explains drilling (science and technology of advanced operations) with

high quality and innovation … a useful reference for academics, researchers,

mechanical, manufacturing, industrial engineers, and professionals familiar

with machining technology.”

—J Paulo Davim, University of Aveiro

exceptional depth of scientific and technical detail

In a presentation that balances theory and practice,Drills: Science and

Technology of Advanced Operations details the basic concepts,

terminol-ogy, and essentials of drilling The book addresses important issues in

drilling operations, and provides help with the design of such operations It

debunks many old notions and beliefs while introducing scientifically and

technically sound concepts with detailed explanations

Manufacturing and Industrial Engineering

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A d v a n c e d O p e r a t i o n s

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Contents

Preface xv

Acknowledgments xxv

Author xxvii

Chapter 1 Drilling System 1

1.1 Fundamentals 1

1.1.1 Basic Drilling Operations 1

1.1.2 Machining Regime in Drilling Operations 4

1.1.2.1 Cutting Speed 5

1.1.2.2 Feed, Feed per Tooth, and Feed Rate 5

1.1.3 Depth of Cut and Material Removal Rate 7

1.1.4 Cut and Its Dimensions 8

1.1.5 Selecting Machining Regime: General Idea 10

1.1.6 Cutting Force and Power 13

1.1.6.1 Definition of Terms According to ISO Standard 13

1.1.6.2 Basis of the Cutting Force and Power Calculations 13

1.2 Drilling System for HP Drills: Structure, Properties, Components, and Failure Analysis 15

1.2.1 System Concept 15

1.2.2 Drilling System 20

1.2.2.1 Structure of the Drilling System 20

1.2.2.2 Coherency Law 21

1.2.2.3 System Objective 22

1.2.3 Case for HP Drills 22

1.2.4 Design of Drilling Systems 25

1.2.4.1 Part Drawing Analysis and Design of the Tool Layout 27

1.2.4.2 Drill Selection/Design 28

1.2.4.3 Drill Material Selection 32

1.2.4.4 HP Drill Design/Geometry Selection 33

1.2.4.5 Part-Holding Fixture Design/Selection 34

1.2.4.6 Metal Working Fluid 35

1.2.4.7 Controller 35

1.2.4.8 Machine Tools 37

1.2.4.9 Tool Holders 40

1.2.5 Summary: Checklist of Requirements for the Drilling System for HP Drilling 49

References 52

Chapter 2 Tool Failure as a System Problem: Investigation, Assessment, and Recommendations 55

2.1 Traditional Notions and Approaches 57

2.2 Failure: A System-Related Definition 58

2.3 Tool Failure Prime Sources 58

2.4 Preparation Stage: Collecting Information 59

2.4.1 Knowing That a Failure Occurs 59

2.4.2 Tool Tracking: The Tag System 59

2.4.3 Automated Tool Tracking with RFID 60

2.4.4 Collecting Other Supporting Information and Evidences 63

2.4.5 Assessment of the Collected Evidences: Obvious Root Causes 64

2.4.6 Additional Information Needed for Normal Tool Failure Analysis 68

2.4.6.1 Tool Drawing 69

2.4.6.2 Tool Layout 69

2.4.6.3 Tool Inspection Report 70

2.4.6.4 Part Inspection Report 70

2.4.6.5 Drilling System Background Information 70

2.4.6.6 Additional Information if the Problem Was Solved 73

2.4.6.7 Tool History 73

2.4.6.8 Inventory Count and Delivery Schedule for the Next Supply 73

2.5 Part Autopsy and Tool Reconstruction Surgery 73

2.5.1 Example: Step 1—Failure Information 74

2.5.2 Example: Step 2—Analysis of the Collected Failure Information 75

2.5.3 Example: Step 3—Sectioning the Autopsy Specimen 75

2.5.4 Example: Step 4—First Microscopic Examination of the Sectioned Part 78

2.5.5 Example: Step 5—Breaking the Precut Section and Separating Debris/Tool Fragments 78

2.5.6 Example: Step 6—Examining the Surface of the Machined Hole 80

2.5.7 Example: Step 7—Reconstruction of the Bottom of the Hole Being Drilled 81

2.5.8 Example: Step 8—Reconstruction of the Drill and Root Cause Determination 82

2.5.9 Example: Step 9—Archiving the Evidence and Writing a Report 84

2.6 Tool Wear 85

2.6.1 Background Information 85

2.6.2 Standard Wear Assessment 88

2.6.3 Statistical Analysis of Tool Wear Curves 91

2.6.4 Common Wear Regions of Drills 99

2.6.5 Assessment of Tool Wear of HP Drills 103

2.6.6 Correlations of Drill Wear with Force Factors 104

2.6.7 Assessment of Wear Resistance of Tool Materials 105

2.6.8 Real Mechanisms of Tool Wear: Pure Abrasion, Adhesion, and Abrasion–Adhesive Wear 107

2.6.9 Special Wear Mechanisms: Reaction of the Cutting Tool on Increased Cutting Speed and the Optimal Cutting Temperature 111

2.6.9.1 Prevailing Concept 111

2.6.9.2 Optimal Cutting Temperature: Makarow’s Law 115

2.6.10 Special Wear Mechanisms: PCD 116

2.6.11 Casting Defects and Tool Wear/Failure 126

2.6.12 Special Wear Mechanisms: Cobalt Leaching 130

2.6.13 Facts and Physics of the Wear of Tool Materials 133

2.6.13.1 Need for a New Theory of Tool Wear 133

2.6.13.2 Diffusion Self-Healing of Microcracks 137

References 139

Chapter 3 Tool Materials 143

3.1 Words of Wisdom 143

3.2 Basic Properties 144

3.2.1 Wear Resistance 145

3.2.2 Toughness 145

3.3 High Speed Steels 147

3.3.1 Why HSSs? 147

3.3.2 Brief History 148

3.3.3 Common Grades of HSS 149

3.3.3.1 Group I: General-Purpose HSSs 150

3.3.3.2 Group II: Abrasion-Resistant HSSs 150

3.3.3.3 Group III: High Red Hardness HSSs 150

3.3.3.4 Group IV: Super HSSs 151

3.3.4 Factors Affecting Intelligent Grade Selection of HSS 151

3.3.5 Formation of Properties 154

3.3.5.1 Casting of HSS 156

3.3.5.2 Dealing with Cast Structure 158

3.3.6 Components in HSS 167

3.3.6.1 Tungsten and Molybdenum 167

3.3.6.2 Chromium 167

3.3.6.3 Vanadium 168

3.3.6.4 Cobalt 168

3.3.6.5 Carbon 168

3.3.6.6 Sulfur 168

3.3.7 Heat Treatment of HSS 170

3.3.7.1 Soft Annealing and Stress Relieving 170

3.3.7.2 Hardening and Tempering 171

3.3.7.3 Cryogenic Treatment of HSSs 173

3.3.8 Coating of HSS 175

3.4 Cemented Carbides 179

3.4.1 What Is Cemented Carbide? 180

3.4.2 Brief History 180

3.4.3 Grade Classification 182

3.4.3.1 Earlier Standards 182

3.4.3.2 Current Standard 183

3.4.4 Problem 186

3.4.5 Properties of Cemented Carbides 187

3.4.5.1 Introduction Notes 187

3.4.5.2 Groups of Properties 188

3.4.5.3 Formation of Properties: Basics 189

3.4.5.4 Some Important Properties 190

3.4.5.5 Nondestructive Testing of Carbide Properties Using Magnetic Measurements 197

3.4.5.6 Nanoparticle Carbides: Research and Expectations 206

3.4.6 Carbide Blanks 207

3.4.6.1 Blanks for Carbide-Tipped Drilling Tools 208

3.4.6.2 Round Carbide Blanks 210

3.4.6.3 Round Carbide Blanks Made of Advanced Carbides 214

3.4.7 Coating 216

3.4.7.1 Methods of Application 216

3.4.7.2 Coating Strategies 220

3.4.7.3 Quality Control 222

3.4.8 Cryogenic Treatment of Cemented Carbides 226

3.4.9 Considerations in Proper Grade Selection 228

3.5 Diamond 230

3.5.1 Introduction 230

3.5.2 Blanks for Drilling Tools: PDC and PCD Disks 231

3.5.3 Manufacturing of PCD Disks 234

3.5.3.1 Process 234

3.5.3.2 Powder Mix 238

3.5.4 Grain Size 241

3.5.5 Interfaces 244

3.5.6 Thermal Stability 245

3.5.7 PCD Grade Selection and Quality Inspection 250

3.5.7.1 Grade Selection Considerations 250

3.5.7.2 Quality Assessment of PCD Products 253

References 255

Chapter 4 Twist and Straight-Flute Drills: Geometry and Design Components 259

4.1 Classification 260

4.2 Basic Terms 265

4.3 Constraints on the Drill Penetration Rate: Drill 268

4.4 Force Balance as the Major Prerequisite Feature in HP Drill Design/Manufacturing 269

4.4.1 Theoretical (Intended) Force Balance 269

4.4.2 Additional Force Factors in Real Tools 271

4.4.3 Resistance of a Drill to the Force Factors 272

4.4.3.1 Resistance to the Drilling Torque 273

4.4.3.2 Resistance to the Axial Force 276

4.4.3.3 Drill-Design/Process-Related Generalizations/ Considerations Related to Resistance to the Force Factors 284

4.4.3.4 Improving Drill Rigidity 287

4.4.3.5 Axial Force (Thrust)–Torque Coupling 290

4.5 Drill Geometry 291

4.5.1 Importance of the Drill Geometry 291

4.5.2 Tool Geometry Measures to Increase the Allowable Penetration Rate 292

4.5.3 Straight-Flute and Twist Drills Particularities 292

4.5.4 Systems of Consideration 295

4.5.5 Drilling Tool Geometry in T-hand-S: Rake and Clearance Angles 296

4.5.6 Drilling Tool Geometry in T-mach-S and T-use-S: Clearance Angles 307

4.5.7 Drilling Tool Geometry in T-mach-S and T-use-S: Rake Angles 314

4.5.7.1 Rake Angle in T-mach-S/T-use-S γcf Determination According to the First Approach 315

4.5.7.2 Rake Angle in T-mach-S/T-use-S γne Determination

According to the Second Approach 318

4.5.7.3 Comparison of the First and Second Approaches 323

4.5.7.4 Chip Breakage 328

4.5.8 Chisel Edge 336

4.5.8.1 General 336

4.5.8.2 Case 1: The Primary Flank Is Planar and Its Width Is Equal to or Greater than 2a o 337

4.5.8.3 Case 2: The Primary Flank Is Planar and the Width of the Primary Flank Is Equal to a o 346

4.5.8.4 Drill Flank Is Formed by Two Surfaces (Generalization: Tertiary Flank Plane and Split Point) 350

4.5.8.5 Modifications of the Chisel Edge 359

4.5.9 Point Angle and Margin 366

4.5.9.1 Axial/Radial Force Ratio 368

4.5.9.2 Uncut Chip Thickness (Chip Load) and Chip Flow 368

4.5.9.3 Exit Burr and Delamination 369

4.5.9.4 Cycle Time 372

4.5.9.5 Back Taper 372

4.5.9.6 Margin and Minor Cutting Edge 377

4.6 Drill Design Optimization Based on the Load over the Drill Cutting Edge 384

4.6.1 Uncut Chip Thickness in Drilling 385

4.6.2 Load Distribution over the Cutting Edge 386

4.6.3 Drills with Curved Cutting Edges 387

4.6.4 Generalization 393

References 394

Chapter 5 PCD and Deep-Hole Drills 397

5.1 PCD Drilling Tools 397

5.1.1 Challenges of Work Materials 397

5.1.1.1 Metal-Matrix Composites 397

5.1.1.2 Polymer-Based Composite Materials 399

5.1.1.3 Similarity and Differences 401

5.1.2 PCD-Tipped Drilling Tools 401

5.1.3 Full-Face (Cross) PCD Drills 407

5.1.3.1 First Approach: PCD Is Sintered in a Part of the Drill Body 407

5.1.3.2 Second Approach: PCD Segment(s) Is Brazed into the Drill Body 416

5.2 Deep-Hole Drills 427

5.2.1 Introduction 427

5.2.2 Common Classification of Deep-Hole Machining Operations 428

5.2.2.1 Force Balance and the Meaning of the Term Self-Piloting Tool 430

5.2.3 Additional Force Factors in Real Tools 432

5.2.4 Common Feature of SPTs: Supporting Pads 434

5.2.4.1 Locating Principle of SPTs 434

5.2.4.2 Optimal Location of the Supporting Pads 440

5.2.4.3 Location Accuracy of the Supporting Pads 444

5.2.5 Gundrills 450

5.2.5.1 History 450

5.2.5.2 Basic Design and Geometry 451

5.2.5.3 Chip Breaking 453

5.2.5.4 Common Recommendations on the Selection of Tool Geometry/Design Parameters 456

5.2.5.5 Particularities of the Rake and Flank Geometries 457

5.2.5.6 Shank 463

5.2.5.7 Drivers 468

5.2.5.8 HP Gundrills and Gundrilling 469

5.2.6 STS Drills 491

5.2.6.1 History 491

5.2.6.2 Basic Operations 493

5.2.6.3 Basic Geometry of STS Drills 496

5.2.6.4 Power and Force 498

5.2.6.5 Problem with the Core 502

5.2.6.6 Problem with the Pressure Distribution 504

5.2.6.7 Addressing the Problems 507

5.2.7 Ejector Drills 508

References 520

Chapter 6 Metalworking Fluid in Drilling 523

6.1 Introduction 523

6.2 MWF Application Methods 523

6.2.1 Flood Application 524

6.2.2 Through-Tool MWF Application 526

6.2.3 Near-Dry (Minimum Quantity Lubricant) Application 529

6.2.4 Application of CMWFs 529

6.3 High-Pressure MWF Supply: Theory, Apparatus, and Particularities of Tool Design 529

6.3.1 Flow Rate 529

6.3.2 Pressure 530

6.3.2.1 Definition 530

6.3.2.2 Pressure Measurement 532

6.3.3 Pressure Loss in MWF Supply to the Machining Zone 534

6.3.3.1 Simple Tests to Understand Phenomenology of Pressure Losses 534

6.3.3.2 Electrical Analogy to Comprehend the Relationship between the Flow Rate and Pressure 535

6.3.3.3 Modified Bernoulli Equation 537

6.3.3.4 Types of Flow 538

6.3.3.5 Viscosity 538

6.3.3.6 Reynolds Number 539

6.3.3.7 Major Pressure Losses: Friction Factor 541

6.3.3.8 Minor Losses (Losses Due to Form Resistance) 544

6.3.3.9 Solution of the Reverse Problem 552

6.3.3.10 Practical Coolant Channel Configurations 552

6.3.3.11 Pressure Loss in the Machining Zone 558

6.3.3.12 Total Pressure Loss and the Pressure Needed to Deliver the Desirable Flow Rate 560

6.3.4 MWF Flows Management in the Bottom Clearance Space 560

6.3.4.1 Two-Flute Drills 560

6.3.4.2 Gundrills 565

6.3.5 Coolant Channels Network: Ejector Effect 572

6.4 Near-Dry (Minimum Quantity Lubricant) Drilling Operations: Theory, Apparatus, and Particularities of Tool Design 577

6.4.1 Challenges with MWF 577

6.4.2 Understanding the Subject 578

6.4.3 Implementation Aspects 581

6.4.4 Aerosol (Mist) 581

6.4.4.1 How Aerosol Is Generated 581

6.4.4.2 Aerosol Composition 582

6.4.4.3 Aerosol Parameters Control 583

6.4.5 Classification of NDM 584

6.4.6 Cutting Tool 593

6.4.6.1 Modification to the Tool Geometry 593

6.4.6.2 Modification to Design of Internal Aerosol Supply Channels and Their Outlets (Both Shape and Location) 595

6.4.7 Chip Management 596

6.5 Increasing Tool Life with CMWF 597

6.5.1 Where Does It Hurt? 597

6.5.2 How CMWF Can Reduce Cutting Temperature 598

6.5.3 Why It Works 599

6.6 Application of CMWFs 599

6.6.1 Basics 599

6.6.1.1 Work Material 600

6.6.1.2 Tool Material 600

6.6.2 Commonly Accepted Rationale behind the Use of CMWF 601

6.7 MWF Essential Parameters to Be Maintained in HP Drilling 602

6.7.1 Concentration 603

6.7.2 Water Quality 603

6.7.3 MWF Filtration 604

References 607

Chapter 7 Metrology of Drilling Operations and Drills 611

7.1 Introduction 611

7.2 Standard Reference Temperature 613

7.3 Small-Scale Features 613

7.3.1 Definition of Surface Profile, Cutoff (Sampling) Length, and Centerline 614

7.3.2 Common Characteristics of Surface Texture (Roughness) Used in Drilling Operations 615

7.3.3 Designation of Surface Texture (Roughness) Parameters 619

7.3.3.1 Basic Symbols 619

7.3.3.2 Composition of Complete Graphical Symbol 620

7.3.3.3 Practical Designation on Tool Drawings 623

7.3.3.4 Preferred Surface Roughness 624

7.3.3.5 Different Methods for Designating Surface Texture 626

7.4 Large-Scale Features: Bore Tolerancing 627

7.5 Large-Scale Features: Geometrical Tolerances 630

7.5.1 Concept and Standard Symbols 630

7.5.2 Definitions of Basic Terms 631

7.5.3 Definitions of Geometrical Tolerance-Related Terms 631

7.5.4 Datum Features 638

7.6 Bore Gaging 641

7.6.1 Bore Gage Classification and Specification 641

7.6.2 Components of Gage Accuracy 642

7.6.3 Bore Gage Types 643

7.7 Drill Metrology 643

7.7.1 Drilling Tool Diameter 643

7.7.1.1 Existing Tolerances 643

7.7.1.2 Methodology to Calculate the Drilling Tool Diameter and Its Tolerance Zone 645

7.7.1.3 Assessment of the Results 648

7.7.1.4 Drill Diameters in the Tool Drawing 650

7.7.2 Shank Diameter 650

7.7.3 Overall Length/Flute Length/Shank Length 651

7.7.4 Datum 654

7.7.5 Runout (Straightness) 656

7.7.5.1 Concept 656

7.7.5.2 Importance 657

7.7.5.3 Method of Measurement and Tolerancing According to Standards 658

7.7.5.4 Assigning in Drill Drawings 660

7.7.5.5 System Runout 661

7.7.6 Point Angle and Lip Height 665

7.7.6.1 Point Angle Tolerances 665

7.7.6.2 Lip Height Tolerances 666

7.7.6.3 Assigning in Drill Drawings 672

7.7.7 Web Thickness, Centrality (Symmetry) of the Web, and Flute Spacing 672

7.7.7.1 Web Thickness 672

7.7.7.2 Centrality (Symmetry) of the Web 673

7.7.7.3 Flute Spacing 675

7.7.8 Chisel Edge Centrality 677

7.7.9 Back Taper 679

7.7.10 Margin Width 680

7.7.11 Angle of Helix 681

7.7.12 Clearance Angle 683

7.7.13 Surface Roughness 687

7.7.14 Drill Inspection 689

7.7.15 Dimensional Inspection (Metrological) System: Flowchart 690

7.7.16 Dimensional Inspection (Metrological) System: Design Stage 693

7.7.16.1 Diameter-/Length-Related Articles 693

7.7.16.2 Major Reference Plane 695

7.7.16.3 Articles Related to the Major Cutting Edges 701

7.7.16.4 Articles Related to the Chisel Edge and Its Region 706

7.7.16.5 Articles Related to Gashes 709

7.7.16.6 Articles Related to the Coolant Holes 711

7.7.16.7 Dealing with Nonincluded Articles 712

7.7.17 Dimensional Inspection (Metrological) System: Planning Stage 712

7.7.17.1 Simple Gages 712

7.7.17.2 Optical Microscopes/Measuring Systems 713

7.7.17.3 Specialized Measuring Microscopes 717

7.7.17.4 CNC Measuring Systems 725

7.7.17.5 Summary 733

References 734

Appendix A: Axial Force, Torque, and Power in Drilling Operations 735

Appendix B: Tool Material Fundamentals 747

Appendix C: Basics of the Tool Geometry 789

Preface

Why don’t you write books people can read?

Nora Joyce to her husband James (1882–1941)

Various studies and surveys indicate that hole making (drilling) is one of the most time-consuming metal cutting operations in the typical shop It is estimated that 36% of all machine hours (40% of computer numerical controlled [CNC] machines) is spent performing hole-making operations, as opposed to 25% for turning and 26% for milling, producing 60% of chips Therefore, the use of high-performance drilling tools could significantly reduce the time required for drilling operations and thus reduce hole-making costs

Over the past decade, the tool materials and coatings used for drills have improved dramatically New, powerful, high-speed spindles, rigid machines, proper tooling including precision workhold-ing, and high-pressure, high-concentration metal working fluid (MWF) have enabled a significant improvement in the quality of drilled holes and an increase in the cutting speed and penetration rate

in drilling operations In modern machine shops, as, for example, in the automotive industry, the quality requirements for drilled holes today are the same as they used to be for reamed holes just

a decade ago The cutting speed over the same time period has tripled and the penetration rate has doubled

Despite all these new developments, many drilling operations even in the most advanced facturing facilities remain the weakest link among other machining operations Moreover, there

manu-is still a significant gap in the efficiency, quality, and reliability of drilling operations between advanced and common machine shops This is due to a lack of understanding of not only the process and its challenges, but primarily of the design, manufacturing, and application methods of high- productivity (HP) drilling tools It is totally forgotten that process capability, quality, and effi-ciency are primarily decided on the cutting edges of the drill as this tool does the actual machining while all other components of the drilling system play supporting roles presumably assuring drill best working conditions Therefore properly designed and manufactured drilling tools for a given application is the key to achieving high efficiency in drilling operations Such a tool is referred to as the high-productivity drill (HP drill) throughout the book

WHY NOW?

Although the basic design and manufacturing principles of drilling tools have been studied and used since the time that the Great Pyramids were built, the implementation of the results of these studies has been rather modest The most apparent cause for this is that these studies lacked a sys-temic approach; that is, one component, for example, tool life, was studied while other important parameters, for example, process efficiency, were not considered Although this is true, it is not the real cause The reality is that neither the machining system, as a whole, nor its components were ready for implementation of the advances made in the design and manufacturing of drilling tools

In the not-too-distant past, the components of a machining system were far from perfect, and thus it was not possible to utilize the advantages of advanced drilling tools Tool specialists were frustrated old machines with insufficient power and spindles that could be rocked by hands; part fixtures that clamped parts differently every time; part materials with inclusions and great scatter in essential properties; tool holders that could not hold tools without excessive runouts assuring their proper position; starting bushing and bushing plates that had been used for years without replace-ment; low-concentration often contaminated MWFs that were more damaging than beneficial to the

cutting tool; manual sharpening and presetting of cutting tools; limited range of cutting speeds and feeds; low dynamic rigidity of machines, etc The most advanced (and thus expensive) drilling tools, therefore, performed practically the same (or even worse) as basic tools made in a local tool shop As

a result, any further development in tool improvement was discouraged as leading tool manufacturers did not see any return on investment in such developments

For many years, a stable though fragile balance was maintained between low-quality (and thus relatively inexpensive) drilling tools and poor machining system characteristics Metal cutting research was attributed mainly to university labs, and their results were mostly of academic inter-est rather than addressing practical needs It is clear that metal cutting theory and the cutting tool designs based on this theory were not requested as many practical specialists had not observed any application benefits of such tools, and thus the theory behind them

This has, however, changed rapidly since the beginning of the twenty-first century as global petition forced many manufacturing companies, mainly automotive manufacturers, to increase the efficiency and quality of machining operations To address these issues, leading tool and machine manufacturers have developed a number of new products—new powerful precision machines hav-ing a wide range of speeds and feeds, tool materials and coatings, new tool holders, automated

com-workholding fixtures, advanced machine controllers, etc These changes can be called the silent

machining revolution as they are rather dramatic and happened in a short period of time For ple, the 2013 Hanover Fair, the world’s largest trade show for industry, was intended to be the drive toward the fourth industrial revolution Unfortunately, it was not noticed by many tool manufactur-ers or even researchers Therefore, the following text lists a few significant changes that can barely

exam-be seen in university labs and machine shops

MACHINE TOOLS

Dramatic changes in the design and manufacturing of machine tools can be summarized as follows:

1 Machines with powerful digitally controlled truly high-speed motor spindles: For ple, machines with working rotational speeds of 25,000 rpm and 35 kW motor spindles are used in advanced manufacturing power train facilities in the automotive industry New multiaxis CNC machines with an excess of power and spindles capable of 35,000 rpm rotational speed are also being rapidly introduced in the mold-making industry

2 New spindles that assure tool runout <0.5 μm: These were implemented on many machines High static and dynamic rigidity of such spindles and machines made with granite beds results in chatter (vibration)-free performance even at the most heavy cuts in truly high-speed machining conditions

3 High-pressure through-tool MWF supply: New machines are equipped with a sure (70 bar and more if needed) MWF (coolant) supply through the cutting tools to pro-vide cooling and lubrication needed for high-speed operations MWFs cleaned up to 5 μm are delivered at constant controlled temperatures suitable for a given machining operation

high-pres-T ool H olders and T ool P reseTTing P racTice

Old-fashioned tool holders having 7/24 taper developed over half a century ago and sold today as CAT,

BT, and ISO are being rapidly replaced with high-precision HSK, developed as a standard defined by DIN (German Institute for Standardization) Balanced hydraulic, shrink fit, and steerable tool holders have been developed and widely implemented for high-speed machining to minimize tool runout and to maximize tool holding rigidity With shrink fit tool holders, vibration is reduced and cutting is notice-ably faster and smoother due, in part, to the lack of set screws and component tolerance variances.For years, tool presetting was one of the weakest links in assuring proper tool position and per-formance No matter how good the tool and its tool holder are tool presetting accuracy determines

the actual performance of the tool Need for more accurate tool presetting, tool data ity from the presetter to the machine tool controller, and tool performance traceability has led to the development of noncontact laser-automated tool presetting machines Nowadays, tool presetting machines (e.g., Zollar and Kelch) are widely used in high-speed machining applications Each tool contains an ID number to enable users to retrieve and use the data later on The tool is mounted into the holder, and the CNC-driven tool length stop is set to ensure correct tool positioning—for example, tool tip to gage datum Measurement results are transferred to the tool radio-frequency identification chip (e.g., the Balluff chip) embedded in the holders (see Chapter 2 for a detailed explanation) Such a presetting machine can provide accuracy within 3 μ on each tool, which, in turn, results in improved machining quality.

transformabil-a dvanced c uTTing P rocess M oniToring

Many recent technologies offer tool and machine monitoring, from detecting tool presence to suring the tool’s profile Some can even measure the power consumed by the spindle motor and use that information to control the feed rate and minimize machining time The most common features of modern machine tool controllers developed for high-speed unattended manufacturing are as follows:

mea-• Detecting broken or absent tools: Small, simple tool detectors that check for the

pres-ence of a drill or other cylindrical-shaft tool were developed and implemented on modern machine tools Their small size and simple operation adapt them well for many environ-ments, including machining centers, screw machines, and transfer machines

• Power monitoring: Directly monitoring the power consumed by the spindle motor allows

one to understand exactly what is happening with the tool in a drilling operation Power monitoring systems take their data directly from the motor controller; others measure with

transducers on the wiring to the motor This is called the sensory perception of machines

The system obtains information that would not otherwise be detectable and notifies the operator as soon as possible when there is a problem

• Adaptation: Not only can power-monitoring units detect broken or worn tools, but with an

adaptive control option, they can also use them to control the feed rate, reducing machining time, yet extending tool life by keeping the tool load constant and well under maximum load

a dvances in c uTTing T ool M aTerials

Improvements in the quality and consistency of the major groups of tool materials through menting advanced tool materials technologies are of prime importance (see Chapter 3 for details) Improved quality of machining systems allows wide use of modern grades of polycrystalline dia-mond (PCD) tool material capable of milling, drilling, and reaming high-silicon aluminum alloys at speeds of 1,000–11,000 m/min Modern grades of carbide tools combined with advanced coatings allow machining of alloyed steels at speeds of 300–600 m/min Modern grades of polycrystal-line cubic boron nitride (PCBN) allow hard machining operations, which substitute some grinding operations New tool materials and advanced grades of existing tool materials, including nanocoat-ings, have also been introduced

imple-a dvances in c uTTing T ool M anufacTuring

A number of significant advances in cutting tool manufacturing are taking place rapidly The duction of CNC tool grinders/sharpeners and CNC tool geometry inspection/measuring machines are probably the most significant

intro-For decades, manual tool grinding/sharpening machines were used in the cutting tool industry It was not possible to maintain the geometry of ground/sharpened tools with reasonable accuracy, as

this varied significantly from tool to tool The exact tool geometry simulated by any advanced tool design program couldn’t be reproduced with reasonable accuracy using such machines It was also not possible to grind any complicated profile of the tool as might be required for optimal tool per-formance Naturally, any advanced tool geometry suitable for optimal performance of a machining

operation was bluntly rejected by machining practice as being impractical for a real world application.

This situation, however, has been changing rapidly since the beginning of the twenty-first tury Today’s tool grinder is typically a CNC machine tool that usually has 4, 5, or 6 axes designed

cen-to produce drills from a carbide rod Such machines are widely used in the cutting cen-tool industry High levels of automation, as well as automatic in-machine tool measurement and compensation, allow extended periods of unmanned production Modern CNC tool grinding machines have the following distinctive features:

• Built-in 3D simulation This wizard automatically simulates the tool in 3D, directly in the user interface, and displays the expected cycle time This is accomplished directly on the machine so that an offline simulator is not needed

• The traveling steady unit on the P-axis for accurate long-length tools This provides three points of support to the tool Each support applies continuous hydraulic pressure on the tool, even for reducing diameters, such as tools with a back taper

• Vibration elimination techniques and process options that allow one to grind low surface roughness or mirror surface finishes

• Consistent results of less than 3 μ runout of the tool holding

• On-board measuring systems that are able to measure the ground tool in its original ing inside the grinding machine

clamp-• Robotic loading–unloading and automated grinding wheel changer

No matter how good the fully optimized cutting tool geometry is (using, e.g., a FEM simulation software) and how well it is depicted in multiple section planes on the tool drawing made using a 3D CAD program, it is practically useless as such an optimized geometry cannot be reproduced and then inspected/measured with high accuracy Until very recently, the most common practice of measuring tool geometry was manual inspection, which did not provide accurate results as it was dependent on how experienced the inspector was, the complexity of the tool, and many other fac-tors that could not be controlled Naturally, the accuracy of such an inspection was not sufficient to ensure the effective performance of HP drills

To address this important issue, CNC tool inspection machines that are capable of inspecting ting tools accurately have been developed (see discussion in Chapter 7) For example, the ZOLLER Genius 3 measuring and inspection machine is equipped with five CNC-controlled axes for measur-ing and inspecting virtually any tool parameter—it is fast, simple, precise to the micron, and fully automatic Equipped with a 500-fold magnification incident light camera, Genius 3 can automatically inspect microtools The machine includes measuring programs for virtually every parameter (radius contour tracing, effective cutting angle, clearance angle, helical pitch and angle, chamfer width, groove depth, tumble and concentricity compensation, step measurement, etc.) of cutting tools

cut-d rilling T ools as THe W eakesT l ink

The preceding discussion suggests that many components of modern drilling systems are ready

to fully support HP drills while the equipment available to tool manufacturers fully support their high-efficiency production with practically no restrictions However, wide implementation of HP drilling tools is not yet the case As a result low reliability of cutting tools and sporadic tool failures

in advanced manufacturing facilities (i.e., in the automotive industry) are major hurdles in the way

of wide use of efficient, unattended machining production lines and manufacturing cells to decrease direct labor costs and improve efficiency of machining operations As such, significant downtime

due to low reliability of drilling tools undermines the potential of highly efficient production lines and manufacturing cells, raising questions about the feasibility of unattended machining operations.

r eadiness of T ool u sers and M anufacTurers To a ddress THe i ssue

The preceding discussion clearly indicates that all the common excuses of inferior tool performance, that is, subpar quality of machining operations, have been practically eliminated Cutting tool users/machining operation designers/planners and cutting tool manufacturers have been pushed to the forefront to show their capability in producing and implementing advanced tools to address the new challenges in metal machining—high productivity rates, low-cost parts, great quality, and suitable tool reliability, particularly for unattended production lines and manufacturing cells

Leading drilling tool manufacturers failed miserably to meet this new challenge The root cause for this failure was insufficient understanding of drilling principles, including drilling tool geom-etry and drill manufacturing quality–related flaws This is partially due to the lack of information

in the literature where all aspects of drilling tools are explained The few available papers on drill geometry present the results in differential geometry, matrix, and vectorial forms not comprehen-sible to many technical readers It is not clear from the available literature sources why one should learn drilling tool geometry as no practical examples of geometry optimization are normally con-sidered in the literature In other words, the tooling industry is left with no proper scientific or even engineering support The technical and reference literature present a mixture of old and new notions

as technical data have been copied from one edition to the next for the last 50 years or more It is

therefore very difficult for a practical engineer to separate the wheat from the chaff as information

is thoroughly mixed in the technical literature and on various technical websites

AIM OF THE BOOK

The foregoing analysis suggests that the weakest link in the design of HP drilling operations is the readiness of cutting tool users/machining operation designers/planners and cutting tool manu-facturers The lack of relevant research work on modern hole-making operations just adds to the problem This book aims to address the most important issues in drilling operations and thus to provide assistance with the design of such operations It discards many old notions and beliefs and introduces scientifically and technically sound notions with detailed explanations

UNIQUENESS OF THE BOOK

The major feature of this book is the introduction and development of the concept of high-productivity (HP) drill design and its manufacturing and application features A frequently asked question con-cerns the difference between HP drills and normal drills In other words, what makes a drill an HP

drill? The answer to this is discussed in the system approach combined with the VPA-Balanced©

design concept discussed in Chapter 1 This combination can be briefly described as follows

The VPA-Balanced design concept is the methodology used to design and manufacture a drill

following a set of rules:

1 The geometry of the drill point is designed for a particular work material so that it ensures

a Minimum axial force and drilling torque (Chapter 4)

b Balanced design of the major cutting and chisel edges to guarantee chip flows from the different cutting edges with no crossing/interference and to provide sufficient room to ensure there are no restrictions on these flows (Chapters 4 and 5)

c Perfect force balance of a VPA-Balanced drill due to proper designing and turing tolerances (Chapter 7)

manufac-d Proper distribution of MWF flow in the machining zone (Chapters 5 and 6)

2 The drill material is selected to be

a Of high quality and consistency (Chapter 3)

b Application specific

3 The drill should be of high manufacturing quality (Chapter 2), including final inspection

of the tool (Chapter 7)

Although an HP drill designed adhering to the VPA-Balanced design concept is fully capable of

ensuring the highest possible productivity of a given drilling operation, this capability is realized if and only if it is fully supported by the drilling system and its components Are HP drills universal? No, they are not They can be compared to high-performance cars, which require good road conditions, highly qualified drivers, and careful maintenance High-performance cars may not be suitable for country roads, subpar maintenance, or for carrying heavy loads while moving from one apartment to the next Moreover, they are not meant for everyday commuting from home to the workplace and back

at an average speed 40 km/h However, when the conditions are ideal, they deliver great comfort, joy

of driving, and incredible reliability As more and more people appreciate these benefits, the market segment of these cars increases quickly This is also true for HP drills They are suitable for high-quality, well-maintained drilling systems They require high-quality tool materials and specialized, application-specific coatings as well as intelligent tool manufacturing systems, including complicated inspection equipment and procedures and computerized presetting in high-quality drill holders The benefits include a high-penetration rate (which in turn results in high productivity), prolonged tool life, tool reliability, and better quality of machined holes—often two- or even three-tool hole operations can be reduced to a single-tool hole operation HP drills are the major trend for the future where unat-tended, fully computerized manufacturing lines with greatly reduced labor cost, high productivity, and high consistency of quality of the manufactured parts are the ultimate goals/requirements

On reading the previous paragraph, the reader may think this to be a dream or a remote possibility However, this is a reality today, especially in the automotive industry, where manufacturing cells and production lines deliver high productivity (true high-speed machining), with minimum atten-dance, and great quality It is surprising why some people, even specialists, cannot see the obvious results The reliability of cars has increased significantly, allowing bumper-to-bumper warranties

to be extended to 100,000 miles (160,000 km) for many cars There are also a number of other significant improvements such as power-saving lights, reduced weight, more efficient fuel consump-tion, and increased safety However, in spite of these improvements, the cost of these cars has not increased when compared to the cost of other commodities in the market

To conclude this discussion, the author would like to remind the following Only 20 years ago, the practical utility of carbide drills was being debated as their cost was much more than high-speed steel (HSS) drills and their applications required more intelligent handling and resharpening, bet-ter tool holders and machine spindles, etc Many specialists at that time thought that carbide drills would have very limited use in practical manufacturing However, today these drills are common standard tools used universally, while HSS drill usage has reduced significantly The author is con-vinced that this will also be the case with HP drills as the economy of modern manufacturing dic-tates so This book has been written to accelerate wider acceptance of such drills

The distinguishing features of this book are as follows:

1 Drilling is considered in this book instead of drills as is customary in the existent literature on the subject Drilling in this book is considered at two levels: (1) as a metalworking operation and (2) as a process The former covers the steps in the design of optimal drilling operations, and thus is meant for process/machine/manufacturing lines and cell designers/developers, while the latter considers the cutting process with the unique features particular to drilling, and thus is meant for tool/tool materials/CNC tool grinder researchers/developers/designers

2 The concept of a drilling system is introduced, and the interinfluence of the nents of this system such as a drill, drilling machine, tool holder, fixture, coolant, etc.,

compo-are analyzed The coherency law is formulated The so-called component approach is a common manufacturing practice in today’s environment, where different manufacturers produce various components of the drilling system but no one seems to be responsible for system coherency Unpredictable/unexplainable tool failure is a direct result of such

an approach because the cutting tool is normally the weakest link in the machining system

3 A clear objective of a drilling operation is set out The prime system objective is explained

as an increase in the drilling tool’s (drill, reamer, etc.) penetration rate, that is, in drilling productivity

4 Unparalleled drilling tool failure analysis methodology and procedures are considered

Novel procedures such as part autopsy and drill reconstruction surgery are introduced and

explained with detailed examples The HP drill realistic wear mode and wear regions are also discussed

5 Tool materials that are common for making drilling tools are considered from the point

of view of cutting tool design and implementation Old/irrelevant yet common notions about cemented carbide tool material are discarded Instead, relevant properties of this tool material are introduced For the first time, the technology, properties, and manufacturing technology of PCD as a tool material are considered

6 Design, technology, and implementation practices of PCD drills and reamers are considered Vein and sandwich (DPI) drills, PCD-tipped tools, and full cross PCD drills are also included

7 The essentials of drill geometry parameters are considered in a simple yet practical ner for drill designers, users, and grinders The essential design features of known and advanced drilling tools, including HP drills, are discussed in detail

8 The roles, types, and application techniques of MWF (coolant) in drilling operations are considered The physical foundations of high-pressure application techniques of MWFs are discussed Classification of near-dry machining (NDM) or minimum quantity lubrication (MQL) is presented, discussing their advantages and drawbacks The essential components

of the NDM system using a 360° vision approach as the key to successful implementation

of NDM are considered

9 Drilling metrology is considered for the first time in the literature The meaning of the ignations diametric and form tolerances of drilled holes are explained with examples Drill geometry measurements/inspection using modern machines are considered The standard and suggested tolerances for HP drills on drilling tool geometry parameters as well as their inspection are discussed in detail

des-HOW THIS BOOK IS ORGANIZED

The structure of this book is unusual for the literature in the field because its logic is governed by

HP drill design, manufacturing, and implementation theory and practice A summary of the tents of the chapters is listed in the following

con-c HaPTer 1: d rilling s ysTeM

This chapter consists of two logically connected parts The first introductory part presents a short classification of drilling operations It discusses the components of drilling regime: cutting speed, cutting feed, feed rate, and material removal rate with practical examples; that is, it sets the scene for the other chapters by introducing the correct terminology, and precise definitions

of the parameters of the drilling regime The second part introduces the basics of the system approach The structure of the drilling system is defined and the coherency law is formulated The prime objective of the drilling system is established The case for HP drills is considered and discussed The design procedure for drilling systems is considered with practical examples

Discussion on the selection of the proper components of a drilling system for HP drilling is considered, with an emphasis on the best components used in the automotive industry The chapter argues that the quality of the components and equipment available today in drilling systems and

in drilling tool production systems has overgrown the quality of the design and manufacturing of many drilling tools

c HaPTer 2: T ool f ailure as a s ysTeM P robleM : i nvesTigaTion ,

a ssessMenT , and r ecoMMendaTions

This chapter considers drilling tool failure to be a system issue Analyzing the drawbacks of the traditional notions and approaches, a new system-related definition of tool failure is given The chapter argues that any tool failure is a system-related event The causes of drill failure and their proper identification are discussed Detailed procedures and methodology of drill failure analysis

are considered along with examples For the first time in tool failure analyses, part autopsy and tool

reconstruction surgery are introduced and discussed with examples

Standard tool wear measures and tool life analysis using wear curves are covered with cal examples using the Bernstein distribution for the assessment of tool quality and reliability Typical wear regions of drills are considered with an emphasis on the assessment of tool wear

practi-of HP drills Real mechanisms practi-of tool wear are explained, showing that abrasion-adhesive wear

is common in HP drilling Abnormal wear modes due to castings’ defects and cobalt leaching are discussed The influence of the cutting speed on drill life is discussed showing that how the optimal cutting speed law can be applied in the design of HP drills Wear mechanisms of PCD tools are also considered

c HaPTer 3: T ool M aTerials

The selection of a cutting tool material type and its particular grade is an important factor when planning for a successful drilling operation This chapter differs considerably from other chapters/books written on the subject in that it provides the knowledge base and practical information on tool materials for drilling tool designers, manufacturers, and end users The emphasis is on HSS, cemented (sintered) carbides, and PCD tool materials as more than 98% of modern drilling tools are made of these tool materials The chapter also focuses on common errors and misconceptions

in manufacturing and implementation of drilling tools made of these materials It provides in-depth coverage of tool materials, with definitions of terms and notions, detailed explanations of properties related to drilling, and practical examples, which make the chapter self-contained

For the first time in the literature, the proper utilization of PCD in drilling tools has been ered in detail Relevant properties of PCD, its selection, and its technology are considered Common manufacturing flaws in PCD drilling tools are discussed along with examples Recommendations to avoid such flaws are also provided

consid-Each type of tool materials is discussed in detail, covering its most essential properties These are never discussed in the literature on tool materials and are poorly discussed in materials-related sources For example, for cemetery carbide, the carbon balance is considered while for PCD, the concept of thermal stability is explained

c HaPTer 4: T WisT and s TraigHT -f luTe d rills : g eoMeTry and d esign c oMPonenTs

This chapter begins with the classification of various drills and introduces and defines the basic terms involved A detailed explanation of the major constraints on the penetration rate imposed

by the drilling tool itself and the correlation of these constraints with drill design and geometry parameters are provided The force balance is defined as the major prerequisite feature in HP drill design/manufacturing

The importance and system consideration of the drill geometry are explained with examples Drill geometry is considered in the tool-in-hand system (T-hand-S), in the tool-in-machine system (T-mach-S), and in the tool-in-use system (T-use-S) The relevance of these systems to drill geom-etry parameters indicated in the tool drawing and to tool performance is revealed Straight-flute and helical-flute tools are considered in order to help practical tool/drilling process designers to make proper selection of tool geometry parameters for a given application Drill design optimization based on the load distribution on the rake face over the length of the drill cutting edge is introduced and explained with a number of practical drill designs.

c HaPTer 5: Pcd and d eeP -H ole d rills

This chapter discusses the designs and technologies of PCD drilling tools developed to meet the challenges of both new work material and high-speed machining, primarily in the automotive and aerospace industries It discusses the disadvantages of some of the PCD-tipped drills that have been

in use for a long time The chapter points out a number of attempts (with some great successes) that were made in the development of the so-called full-face (cross-PCD) drills, broadly divided into two major design (technological) approaches: (1) PCD sintered in a part of the drill body and (2) fully sintered PCD segment brazed into the drill body The designs of the full face for HP drilling are also introduced

The chapter further discusses classification, geometry, and design of deep-hole drills It deals

with force balance and defines the term self-piloting tool (SPT) The history, design and

applica-tion particularities, and geometries of gundrills, single tube system (commonly referred to as BTA) drills, and ejector drills are considered, with an emphasis on HP drills Particularities of the MWF supply for each of these drill types are considered STS and ejector drilling principles are compared

to discard old notions while presenting information that will be useful for drill users

c HaPTer 6: M eTalWorking f luid in d rilling

This chapter argues that there are three equally important pillars for the successful application of MWF: (1) selection of the proper MWF, (2) delivery of this MWF into point of application, and (3) MWF maintenance The physical delivery of MWFs to the machining zone is considered in this chapter The chapter deals with the physics and technicalities of high-pressure MWF applications in drilling It proves that the MWF flow, more than its pressure, defines the efficiency of high-pressure MWF applications Using gun drilling as a simple example, the chapter reveals major issues that should be considered in the design of hole-making tools with internal high-pressure MWF supply.The chapter further discusses that the costs of maintaining and eventually disposing of MWF, combined with health and safety concerns, have led to heightened interest in either eliminating MWF altogether or limiting the amount of MWF applied As the former is not feasible for many appli-cations, the latter, referred to as near-dry machining (NDM) or minimum quantity lubrication (MQL), is

a current trend in industry This chapter presents a classification of NDM methods, discussing their advantages and drawbacks It considers the essential components of the NDM system, arguing that a 360° vision approach is the key to successful implementation of NDM

The last section of the chapter argues that to realize the full potential of HP drilling, application

of MWF will have to be monitored carefully; if the MWF parameters deteriorate, it can easily turn successful HP drilling operations into disastrous ones in terms of efficiency and productivity Other issues such as concentration, water quality, and filtration are also discussed

c HaPTer 7: M eTrology of d rilling o PeraTions and d rills

This chapter consists of two closely related parts The first part is related to the various tolerances

on the hole being drilled The second part deals with drill metrology For centuries, the metrology of drilling operations was not considered seriously as the tolerances on drilled holes were wide open

Primitive hand gages and eyeballing measurements relying more on common sense and experience than on results of accurate measurements were considered common practice in drill metrology Nowadays, however, with extensive use of HP drills and modern drilling systems, the tolerances on drilled holes have become the same as they used to be recently for reamed or even for ground holes.The chapter introduces a novel concept of the dimensional inspection (metrological) system for HP drills The datum feature for drilling tools as the solid foundation of the drill design and metrology is defined clearly The chapter identifies drill geometrical and dimensional parameters on tool drawings and defines the procedures of their measurement/inspection with various measuring equipment including CNC drill inspection machines The standard tolerances on the drill param-eters are discussed, showing that they are not suitable for HP drills The tolerances for HP drills are also discussed.

a PPendix a: a xial f orce , T orque , and P oWer in d rilling o PeraTions

This appendix discusses the common ways of determining the force factors of drilling and points out some obvious flaws in such a determination The concept of the chip compression ratio is explained

as this is used in the chapters

a PPendix b: T ool M aTerial f undaMenTals

This appendix provides the supporting material for better comprehension of Chapter 3 It includes basics of metallurgical notions/terminology needed to understand the components and heat treat-ment of HSS The manufacturing processes involved and the formation of essential properties for cemented carbides are discussed The history of the development, formation of essential properties, and manufacturing technology of diamond as a tool material are also considered

a PPendix c: b asics of THe T ool g eoMeTry

The major objective of this appendix is to familiarize potential readers with the basic notions and definitions used in the analysis of tool geometry and the correlation of tool geometry parameters with the cutting force It provides the fundamentals and definitions of the involved terminology for better comprehension of Chapters 4 and 5 It explains with examples that among many angles of the cutting tools, the clearance angle is the major distinguishing feature The influence of other angles

on the cutting process and its outcome are also discussed Comprehensive coverage of edge tion and its metrology is included

Acknowledgments

I express my gratitude to all the people who provided support, helped with the testing and mentation of advanced tools, shared their viewpoints and discussed technical issues, allowed me to use their lab, inspection and production equipment, and assisted in the editing this book

imple-I thank Professor J Paulo Davim for encouraging and enabling me to publish this book and many other book chapters that I have written

I thank all my former and present teachers, colleagues, and students who have contributed to my knowledge of the subject

Above all, I thank my wife, Sharon, and the rest of my family, who supported and encouraged me

in spite of all the time spent away from them It was a long and difficult journey for them

Author

Viktor P Astakhov earned his PhD in mechanical engineering from Tula State Polytechnic

University, Tula-Moscow, Russia, in 1983 He was awarded a DSc designation (Dr habil., Docteur d’État) and the title “State Professor of Ukraine” in 1991 for the outstanding service rendered during his teaching career and for the profound impact his work had on science and technology An interna-tionally recognized educator, researcher, and mechanical engineer, he has won a number of national and international awards for his teaching and research In 2011, he was elected to the SME College

pub-as in trade periodicals He hpub-as authored the following books: Geometry of Single-Point Turning

Tools and Drills: Fundamentals and Practical Applications, Tribology of Metal Cutting, Physics

of Strength and Fracture Control, and Mechanics of Metal Cutting He also serves as the editor

in chief, associate editor, board member, reviewer, and advisor for many international journals and professional societies

Everything is designed Few things are designed well.

Brian Reed, American graphic designer

1.1 FUNDAMENTALS

Drilling is a hole-making machining operation accomplished using a drilling tool Figure 1.1a shows a common drilling arrangement in a drilling machine The workpiece is clamped on the machine table with a vice equipped with jaws that clamp against the workpiece, hold-ing it secure The drill is clamped in the machine spindle that provides the rotation and the feed motions Figure 1.1b shows a common drilling arrangement on a lathe The workpiece is clamped in a self-centering three-jaw lathe chuck installed on the machine spindle that pro-vides rotation and the tool is installed on the tailstock engaged with the lathe carriage that provides the feed motion

A drilling tool is defined as an end cutting tool indented for one of the hole-making tions Such a tool has the terminal (working) end and the rear end for its location in a tool holder In all drilling operations, the primary motion is rotation of the workpiece or the tool

opera-or both (counterrotation drilling) and translational feed motion (Figure 1.2), which can be applied either to the tool or the workpiece depending on the particular design of the machined tool used

There are a great number of drilling operations used in modern industry Figure 1.3 shows some of the most frequently used Although all these operations use the same kinematic motions and generic drilling tool definition, the particular tool designs, machining regimes, and many other features of the drilling tools involved are operation specific These basic operations are defined as follows:

1 Drilling is the making of a hole in a workpiece where none previously existed In this case, the operation is referred to as solid drilling If an existing hole (e.g., a cored hole in die casting) is drilled, then the operation is referred to as core drilling A cutting tool called the drill enters the workpiece axially through the end and cuts a hole with a diameter equal to that of the tool Drilling may be performed on a wide variety of machines such as a lathe/turning center and drilling/milling/boring machine

2 Boring (Figure 1.4) is the enlarging of an existing hole A boring tool enters the workpiece axially and cuts along an internal surface to form different features, such as steps, tapers, chamfers, and contours Boring is commonly performed after drilling a hole in order to enlarge the diameter, making steps and special features or to improve hole geometrical quality (i.e., to obtain high-precision diameter and shapes in the transverse [e.g., roundness] and longitudinal [e.g., position deviation] directions) Nowadays, however, many modern boring tools are multi-edge tools allowing significant increase in boring productivity and accuracy

Primary motion—rotation

Feed motion—translation

Drill longitudinal axis

FIGURE 1.2 Motions in drilling.

FIGURE 1.1 Generic drilling: (a) on a vertical drilling machine and (b) on a lathe.

3 Reaming (Figure 1.5) is the enlarging of an existing hole to accurate size and shape

An end cutting tool called the reamer enters the workpiece axially through the end and enlarges an existing hole to the diameter of the tool Reaming is often performed after drilling or boring to obtain a more accurate diameter, better surface finish, and shape in the transverse direction

4 Counterboring is flat-bottomed cylindrical enlargement of the mouth of a hole, usually of slight depth, as for receiving a cylindrical screw head An end cutting tool referred to as the counterbore enters the workpiece axially and enlarges the top portion of an existing hole to the diameter of the tool Counterboring is often performed after drilling to provide space for the head of a fastener, such as a bolt, to sit flush with the workpiece surface

5 Countersinking is the process of making a cone-shaped enlargement at the entrance of a hole An end cutting tool called the countersink enters the workpiece axially and enlarges the top portion of an existing hole to a cone-shaped opening Countersinking is often

FIGURE 1.3 Basic drilling operations.

FIGURE 1.4 Boring.

performed after drilling to provide space for the head of a fastener, such as a screw, to sit flush with the workpiece surface Common included angles for a countersink include 60°, 82°, 90°, 100°, 118°, and 120°.

6 Spotfacing is a drilling operation performed where it is assumed that there will be a highly irregular face surface around a hole This is common with castings The spotface may be either below the surface of surrounding metal or placed on the top of a boss, as is typical with castings The purpose of spotfacing can be either to provide flat surface to accom-modate a screw head, nut, or washer or to make thru face to start other drilling operations The spotface tool resembles an end mill cutter A pilot in the center of the cutting surface

is often added if the alignment of the existing hole and the spotface is important

7 Tapping (Figure 1.6) is a drilling operation of cutting internal threads with an end form tool referred to as the threading tap A tap enters the workpiece axially through the end and cuts internal threads into an existing hole The existing hole is typically drilled by the required tap drill size that will accommodate the desired tap

The cutting speed and cutting feed are prime or basic parameters that constitute the machining regime in drilling operations

FIGURE 1.6 Tapping.

FIGURE 1.5 Reaming: (a) location of the part in the machine spindle, and (b) location of the reamer in the tailstock.

d dr is the drill diameter in millimeters

n is the rotational speed in rpm or rev/min no matter which rotates, the drill or the workpiece

If both the drill and the workpiece rotate in opposite directions (the so-called counterrotation), then

n is the sum of the rotational speeds of the drill, n dr , and the workpiece, n w , that is, n = n dr + n w

For example, if d dr = 10 mm and drill rotates with n = 2170 rpm while the workpiece is stationary, then v = πd dr n/1000 = 3.141 × 10 × 2170/1000 = 68.15 m/min

In the imperial units of measure, the cutting speed is calculated as

v= πd n dr

where

π = 3.141

d dr is the drill diameter in inches

n is the rotational speed in rpm or rev/min

For example, if d dr = ¾ in (19.05 mm) and the drill rotates with n = 1220 rpm while the workpiece

Normally in the practice of machining, the cutting speed v is selected for a given tool design, tool

material, work material, and particularities of a given drilling operation Then the spindle rotational speed should be calculated using Equation 1.1 and the given diameter as

d dr

= 1000

1.1.2.2 Feed, Feed per Tooth, and Feed Rate

The feed motion is provided to the tool or the workpiece, and when added to the primary motion leads to a repeated or continuous chip removal and the formation of the desired machined surface

In all drilling tools, the feed is provided along the rotational axis as shown in Figure 1.2

Figure 1.7 provides visualization of the basic components of the drilling regime such as the cutting feed, depth of cut, and uncut chip thickness commonly referred as the chip load in profes-sional literature Designations of the components of the drilling regime are shown according to the International Organization for Standardization (ISO) Standard 3002/3

The cutting feed, f, is the distance in the direction of feed motion at which the drilling tool

advances into the workpiece per 1 rev and thus, the feed is measured in millimeters per revolution

(inches per revolution) The feed per tooth, f z (the subscript z came from German zahn, i.e., a tooth),

is determined as

f z= z f (1.4)

where z is the number of cutting teeth.

The feed speed (ISO Standard 3002/3) commonly referred to in the literature as the feed rate, v f,

is the velocity of the tool in the feed direction It measures in millimeters per minute (mm/min) or inches per minute (ipm) and calculates as

v f = ⋅f n (1.5)

where

f is the feed (mm/rev or ipm)

n is the rotational speed (rpm)

The feed speed (the feed rate) is often referred to as the penetration rate in the professional erature on drilling It is used as a measure of drilling productivity Substituting Equation 1.3 into Equation 1.5 and arranging the terms, one can obtain

It directly follows from Equation 1.6 that the penetration rate depends equally on the cutting speed and feed This fact should be kept in mind when designing a drilling operation/drill and selecting the tool material and components of a drilling system, for example, the metalworking fluid (MWF) (coolant) supply system.

Although Equations 1.4 and 1.5 are exemplified for drills, they are perfectly valid for all drilling tools shown in Figure 1.3 having the basic motions shown in Figure 1.2

The depth of cut in solid drilling is calculated as a p = d dr /2 In the case of core or pilot hole drilling shown in Figure 1.7b, the depth of cut is calculated as a p = (d dr − d1)/2, where d1 is the diameter of the pilot (core) hole

The material removal rate is known as MRR, which is the volume of work material removed by

the tool per unit time Figure 1.8 presents visualization of the volume of the work materials removed

in solid and core drilling It directly follows from this figure that MMR (measured in mm3/min) in solid drilling is calculated as

dr

dr dr

For solid drilling, these parameters are calculated referring to Figure 1.7a as follows:

The nominal thickness of cut known in the literature as the uncut (undeformed) chip thickness

or chip load is calculated as



  =   sin Φ2 sin Φ2 (1.10)

where Φp is the drilling tool point angle (discussed later in this book in Chapter 4)

The nominal width of the cut known in the literature as the uncut (undeformed) chip width

p

dr p

cross-Example 1.1

Problem

Determine the drill rotational speed, feed speed (the feed rate), depth of cut, material removal rate, nominal thickness of cut (uncut [undeformed] chip thickness or chip load) and width, and nominal cross-sectional area (the uncut [undeformed] chip cross-sectional area) for a drilling operation

⋅

For practical purpose, n = 3185 rpm is adopted.

The feed speed (the feed rate) is calculated using Equation 1.5 as

v f=fn= 0 15 3185 477 75 ⋅ = m m /m in

The material removal rate is calculated using Equation 1.8 as

geo-Example 1.2

Problem

Determine the drill rotational speed, feed speed (the feed rate), depth of cut, nominal thickness

of cut (uncut [undeformed] chip thickness or chip load) and width, and nominal cross-sectional area (the uncut [undeformed] chip cross-sectional area) for a single-cutter boring tool shown in

For practical purpose, n = 1911 rpm is adopted.

The feed speed (the feed rate) is calculated using Equation 1.5 as

v f=f n= 0 10 1911 191 1 ⋅ = m m /m in

The nominal thickness of cut (uncut [undeformed] chip thickness or chip load) is calculated using Equation 1.10 as

The nominal width of the cut (the uncut [undeformed] chip width) is calculated using Equation 1.15 as

b D b D d br d

p

= = ( − ) = − = sin( 1 ) sin .

2 Φ 2 2 19040 35° 2 49 m m

The nominal cross-sectional area (the uncut [undeformed] chip cross-sectional area) is calculated using Equation 1.12 as

A D=h b D D = 0 10 2 49 0 249 ⋅ = m m 2

Selecting the proper speed and feed rate for a particular drilling application is critical to reduce drill wear and breakage as well as to achieve high drilling efficiency in terms of cost per machined hole

In this author’s opinion, the latter is the most proper measure of a drilling tool performance as well

as the efficiency of the drilling operation Therefore, the cutting speed and feed selection is not just technical as it used to be but rather is a process economy-driven issue to achieve the system objec-tive However, such a selection is not as straightforward as it used to be a few decades ago

It used to be that speed and feed recommendations were selected as provided by the literature on

the field For example, one of the most popular resources is Machinery’s Handbook, which celebrated with its 28th edition nearly 100 years as The Bible of the Mechanical Industries The values selected

in this way are always subject to specific job conditions so they were always considered as estimates

to give the process designer/manufacturing specialist/operator an approximate starting point.What makes selecting the right parameters so difficult is that there is little margin for error Speeds and feeds that are too high, as well as speeds and feeds that are too low, can result in low efficiency of the whole operation and can cause drilling tool breakage Moreover, the rapid change

of tool material properties and tool coatings as well as drill design specifics, including the MWF

application technique, overrun the recommendation provided in the reference literature so that, in

many cases, the data provided can no longer be considered a good starting point

Tables 1.1 and 1.2 give some recommendations for the selection of drilling speeds for the purpose

of tool layout design (discussed later in this chapter) Once the design of the whole drilling operation

TABLE 1.1

Speed and Feed Recommendations: HSS Drills

Work Material

Hardness HB

HSS Grade

Cutting Speed (m/min)

Feed (mm/rev) for Drill Diameter (mm)

Free machining steel