Instant High-productivity drilling tools: materials, metrology, and failure analysis, 2nd edition vi
High-Productivity Drilling Tools: Materials, Metrology, and Failure Analysis, 2nd Edition Viktor P. Astakhov
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This completely updated volume covers the design, manufacturing, and inspection of high‑productivity drilling tools (HPDT) and addresses common issues with drilling system components. It discards old notions and beliefs as it introduces scientifically and technically sound concepts and rules with detailed explanations and multiple practical examples.
High‑ProductivityDrillingTools:DesignandGeometry introduces the development of the con cept of high‑productivity (HP) drill design and its manufacturing and application features. This book continues to develop the concept of a drilling system in the new edition and includes new practical examples. It explains how to properly design and manufacture drilling tools for a spe cific application and includes a detailed explanation of the design features, tool manufacturing and implementation practices, metrology of drilling and drilling tools, and the tool failure analysis. Using the coherency law as the guidelines introduced in the first edition, the new edition shows how to formulate the requirements for the components of the drilling system, pointing out that the drill ing tool is the key component to be improved.
This practical book should be on the shelves of all industrial engineers, those working in pro duction and manufacturing, process designers, tool material designers, cutting tool designers, and quality specialists. Researchers, senior undergraduate students, and graduate students will also find this book full of very helpful reference information.
High‑Productivity Drilling Tools
Design and Geometry
Second Edition
Viktor P. Astakhov
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ISBN: 978‑1‑032‑20353‑9 (hbk)
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DOI: 10.1201/9781003263296
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2.2
2.2.1
3.3.3
Preface
Why don’t you write books people can read?
NoraJoycetoherhusbandJames(1882–1941)
MODERN OBJECTIVE OF MACHINING
Reduction of direct manufacturing costs associated with machining operations is a never‑ending challenge for manufacturing plants that have this problem more pressing in recent years because of two prime reasons. The first one is the increased use of special alloys with advanced properties and significant tightening of quality requirements for machined parts. The second one is increasing global competition, which is changing the environment facing most companies today. Previously sheltered from the global market, many manufacturing companies now concern about how to hold and even increase profitability against international competitors.
To meet these challenges, many metal‑machining manufacturing companies strive to reduce cycle times and costs‑per‑parts/units through investing heavily in the increased use of high‑speed, highly‑efficient machining operations and thus changing the whole metal‑machining culture which was around for more than a hundred years. These changes include the utilization of machines with powerful, digitally controlled, truly high‑speed motor spindles; the application of high‑pressure, through‑tool, metal‑working fluid (hereafter MWF) supply; the implementation of high‑precision hydraulic, shrink fit, and steerable tool holders; the integration of advanced cutting process monitor ing; wider use of advanced cutting tool materials; and so on.
These changes can be called the fourth “silent” industrial revolution as they happened in a rather short period of time currently becoming well known as Industry 4.0 initiative. The implementation of the listed developments led to a stunning result: For the first time in manufacturing history, the machining operating time became a bottleneck in the part machining cycle time. As discussed in Chapter 1, in shops with stand‑alone computer numerical controlled (CNC) machines, the machin ing time is 20% of the operating time, whereas in automotive shops, this time reaches 60%. The latter is due to aggressive tool use strategy, elimination of any tool/part inspection in the machine, adjustable pre‑setting of the MWF pressure for each individual tool, automated (robotic) workpiece/ part loading/unloading, using tools with RFID chips, and so on. In both cases, however, the actual machining time is the largest (commonly called as a bottleneck). Knowing these data, one should realize that the implementation of high‑penetration rate tools and well‑designed machining opera tions to reduce machining time has become a vital necessity.
Therefore, the best, most reliable cutting tools of advanced designs, with the best tool materials and the highest possible tool manufacturing quality capable of highly‑efficient machining, should be used in the modern metal‑working industry regardless of their cost as this cost is still virtually insignificant compared to the gain due to increased productivity as the major objective of modern cutting operations. These tools are referred to in this book as high‑productivity (HP) tools.
HIGH‑PRODUCTIVITY DRILLING TOOLS
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 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 HP drilling tools could significantly reduce the time required for machining operations and thus reduce 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 manu facturing facilities remain the weakest link among other machining operations. Moreover, there 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 HP drill ing tools. It is totally forgotten that process capability, quality, and efficiency 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 the 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. However, successful implementation of such tools to achieve high‑productivity drilling operation is achieved if and only if the system concept of drill ing operation (discussed in Chapter 1) is clearly understood and thus properly implemented.
AIM OF THIS BOOK
This book aims to provide in‑depth explanations of the most important aspects in the design and manufacturing of HP drilling tools (with multiple practical examples) for various applications as well as to address the common issues with various important components of the drilling systems to enable one to design/develop effective drilling operations based on the coherency law for drill ing systems introduced and exemplified in this book. It sharply discards many old notions and beliefs while introducing scientifically and technically sound notions/concept/rules with detailed explanations.
UNIQUENESS OF THIS VOLUME
Understanding
One of the most distinguished features of the proposed book is providing explanation to the recom mendations made. It provides a detailed description of the physical/machinal/technological ratio nale behind these suggested recommendations/designs/processes. A real question, however, is “Do we really need understanding of the theory behind HP drilling, and thus the whole essence of metal cutting?” The answer is not as simple as one might think. As long as things proceed well, we do not need to explain or to understand the essence. We drive our cars, watch TV, or use computers without fully understanding of the processes involved. Moreover, explanations and quests for understanding would retard and disturb “normal” course of manufacturing activities including buying and using drilling tools, and receiving awards for excellence in manufacturing. In other words, the explana tions to encourage people to ask inconvenient questions and thus challenge comfortable status quo are discouraged. However, when something goes wrong or breaks down in a production or research activity, or when a competing industrial or scientific group, company, country, etc. achieve better results, so that one is confronted with losing the market or the funding, or even a sector of national economy, then the understanding of the involved processes becomes urgent. It is common, unfor tunately, that such urgency becomes evident too late. In fully applicable to metal cutting and tool design research: when machining time was insignificant in the whole time of part manufacturing,
any research on its improvement was not funded; when machining time became a bottleneck, no research results and specialists are available for the design of efficient machining operations.
Another vital but routinely ignored aspect of the importance of proper explanation belongs to the plane of human psychology. It can be explained with an example from the world of science. In 1847, decades before the germ theory of infection, physician Ignaz Semmelweis suggested that, by wash ing their hands before examinations, doctors could save the lives of many maternity ward patients. He published the results of his many‑year study showing that hand‑washing produced a reduction in maternal mortality to less than 1%, compared to 10%–35% in general practice. Surprisingly, his results were totally rejected by the medical community as many doctors feel offended by his pure evidence‑based finding, and thus a clear suggestion. Needless to say that this suggestion was not followed. The prime reason for that is that Dr. Semmelweis did not offer any scientific rationale why his suggestion works regardless of a great body of meticulously carried experimental study data. Only decades later, when the germ theory of infection was widely adopted in medicine, hand‑wash ing became a routine mandatory procedure as doctors understood why they needed to do so. This example shows the role of the widely accepted theory (or simply, explanations) for even seemingly obvious experimental data or even the result of observation that everyone can see.
FeatUres
The major feature of this book is the introduction and development of the concept of high‑produc tivity (HP) drilling tool design and its manufacturing and application features. The uniqueness of this book can be summarized as follows:
1. For the first time, a clear quantitative detailed explanation of the major objective of mod ern manufacturing as the underlying vital necessity of the design/selection/use of most advanced HP drilling tools is provided. It argues that inthedirectoppositeofprevailing commonnotion in the world‑wide manufacturing and scientific (metal cutting and cutting tools) worlds, the highest quality, and thus the most expensive and reliable, cutting tools must be used in modern manufacturing as a way to reduce the manufacturing cost due to high productivity of such tools.
2. A unique concept of the drilling tool quality is introduced and used as the framework of the book content development. It is to say that throughout this book, the scientific and technological synergy that has been developed among the basic components of drill qual ity such as the tool material, tool design, and tool manufacturing quality is in the focus of attention. This synergy stems from the wide, and thus stable knowledge base and experi ence. The concept and its development throughout this book instill the comprehension of conceptualizing the whole process of the design of HP drilling tools in potential readers.
3 The concept of a drilling system, introduced in the first edition of this book, is further developed with practical examples. The interinfluence of the components of this system such as a drill, drilling machine, tool holder, fixture, and coolant, is analyzed. The coher ency law is introduced.
This book summarized many‑year experience of the author in industry including research, develop ment, manufacturing, implementation, and failure analysis of cutting tools. The author serves as the
cutting tool corporate specialist in Production Service Management, Inc. (PSMi) company, which is a part of the EWIE Group of companies that provides tool commodity management services (including cutting tool development, procurement, application optimization and cost reduction, and failure analysis) for many industries/manufacturing facilities, such as the automotive, aerospace, power, medical, and in many countries that give him truly unique opportunities to visit various manufacturing facilities including cutting tool manufacturing facilities, learn their machining pro cess and cutting tool manufacturing and management practices, investigate cutting tool failures, and understand their needs and goal in the implementation of advanced cutting tools. The author learned that advanced manufacturing runs on tight timelines and high demand, so to gain a com petitive edge, optimization of various machining operations including the use of advanced cutting tools is absolutely paramount. The author has also led a unique assessment program of cutting tool manufacturers for the automotive industry.
I hope that reading this book is worth your time as it covers a number of important pieces of knowledge and information in a systematic manner never covered before. In other words, I hope that the material covered in this book can help you achieve your goals such as improved productivity and quality and reduced unscheduled downtime in performing hole‑making operations.
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 con tents of the chapters is listed in the following.
Chapter 1: Basics of Drilling and Drilling System
This chapter consists of two logically connected parts. The first introductory part presents a short classification of drilling operations. It discusses the components of the drilling regime: cut ting 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 first introduces the basics of the system approach. The structure of the drilling system is defined, and the coherency law is formulated. Then, the chapter introduces a unique concept of cutting tool quality as a synergy of the cutting tool material, tool design, and tool manufacturing quality. The prime objective of the drilling system is established, and major constraints to achieve this objective are considered. The case for HP drills is considered and discussed. The design procedure for drilling systems is considered with practical examples.
Chapter 2: Geometry and Design Components of Drilling Tools
The basic designs and proper geometry of reamers and taps are considered correcting many old notions prevailing in the industry today. Detailed classifications of the features of these tools as well
as the proper definitions of the terms involved are given. The advantages and limitations of form taps are also discussed.
This chapter discusses PCD drills according to the concept of cutting tool quality introduced in Chapter 1. It is to say that the synergy of fundamentals and particularities of the polycrystalline (PCD) tool material, drill manufacturing quality, and drilling tool design is considered. The chapter covers PCD tool material in unparalleled depth from its origin and technology to all facets of its implementation in various drilling tool designs. Thermal stability of PCD was revealed as its weak est feature causing the vast majority of premature failures of PCD tools. It is conclusively proven that overheating on brazing and improper finishing of PCD tools are prime causes of such failures. The practical recommendations on the best practices in brazing and finishing are discussed. The chapter considers various PCD drill designs including the PCD‑tipped drill, full‑face (cross) PCD drills, and full‑head PCD drills. The advantages and disadvantages of these designs/constructions as well as their application particularities including tool drawings are discussed.
Appendix: Basics of the Tool Geometry
The major objective of this appendix is to familiarize potential readers with the basic notions and definitions used in the analysis of tool geometry. It provides the fundamentals and definitions of the involved terminology for better comprehension of Chapters 2–4. Three systems of consideration of the cutting tool geometry are considered, namely tool‑in‑hand (T‑hand‑S) and tool‑in‑use (T‑use‑S), in the proposed, namely the tool‑in‑holder (T‑hold‑S), systems. The relevancy of these systems is explained, and the corresponding angles are clearly defined with graphical supports. The geometri cal relationships among the introduced angles are established. The chapter 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.
Acknowledgments
I express my gratitude to all the people who provided support, helped with the testing and imple 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 of this book.
I thank all my former and present teachers, colleagues, and students who have contributed to my knowledge of the subject.
My special thanks go to Mr. Scott Burke, CEO of EWIE Group of companies, and Mr. Todd Markel, CEO of PSMi company, for their continuous support over many years, toleration of my unorthodox ideas, and providing me with multiple opportunities to research, test, and implement advanced cutting tools, and thus to develop my knowledge, skills, and abilities within the industry.
Above all, I thank my wife, Sharon, and the rest of my family, who supported and encouraged me in spite of the numerous days, evenings, and weekends devoted to writing this book, they provided a loving family environment that afforded me the tranquility and peace of mind that made writing this book possible. This book is dedicated to 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 dur ing his teaching career and for the profound impact his work had on science and technology. An internationally 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 of Fellows.
Besides his teaching engagements, Dr. Astakhov currently serves as the tool research and applica tion manager of Production Service Management Co., which is a part of EWIE Group of companies, a large international tool management company that provides tooling services to many industries such as the automotive, aerospace, power, medical, and others. He has published monographs and textbooks, book chapters, and many papers in professional journals as well as in trade periodicals. He has authored the following books: Drills:ScienceandTechnologyofAdvancedOperations, MetalWorkingFluids:FundamentalsandRecentAdvances, GeometryofSingle‑PointTurning ToolsandDrills:FundamentalsandPracticalApplications, TribologyofMetalCutting, Physics ofStrengthandFractureControl, and MechanicsofMetalCutting. He also serves as the editor in chief, associate editor, board member, reviewer, and advisor for many international journals and professional societies.
1 Basics of Drilling and Drilling System
Everything is designed. Few things are designed well.
BrianReed,Americangraphicdesigner
1.1 BASIC DRILLING OPERATIONS
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, holding 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 provides 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 operations. 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 or both (counter rotation drilling) and secondary motion, which is translational feed motion (Figure 1.2), which can be applied either to the tool or to the workpiece depending on the particular design of the machine tool used.
FIGURE 1.1 Generic drilling: (a) on a vertical drilling machine and (b) on a lathe.
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. Dr illing 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 known as a machining center.
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 qual ity (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 a significant increase in boring productivity and accuracy.
FIGURE 1.2 Motions in drilling.
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 roughness, and shape in the transverse direction.
4. Counterboring is a 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
FIGURE 1.3 Basic drilling operations.
FIGURE 1.4 Bor ing.
the top portion of an existing hole to a cone‑shaped opening. Countersinking is often per formed 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 the surrounding metal or placed on the top of a boss, as is typical with castings. The purpose of spotfacing can be either to provide a flat surface to accommodate a screw head, nut, or washer or to make true face to start other drilling oper ations. 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.
FIGURE 1.5 Rea ming: (a) location of the part in the machine spindle and (b) location of the reamer in the tailstock.
FIGURE 1.6 Tapping.
1.2 M ACHINING REGIME IN DRILLING OPERATIONS
The cutting speed and cutting feed are prime or basic parameters that constitute the machining regime in drilling operations.
1.2.1 cUtting speed
In metric units of measure (the SI system), the cutting speed is calculated as
where π = 3.141, d dr is the drill diameter in millimeters, and 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, nw, that is, n = n dr + nw.
For example, if d dr = 10 m m and drill rotates with n = 2 ,170 r pm while the workpiece is stationary, then ν = π d dr n /1,000 = 3.141 × 10 × 2,170/1,000 = 68.15 m/min.
In the imperial units of measure, the cutting speed is calculated as
where π = 3.141, d dr is the drill diameter in inches, and n is the rotational speed in rpm or rev/min.
For example, if d dr = ¾ in. (19.05 m m) and the drill rotates with n = 1,220 r pm while the work piece is stationary, then ν = π d dr n /12 = 3.141 × 3/4 × 1,220/12 = 239.5 sfm.
Although Eqs. (1.1) and (1.2) 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. To calculate the cut ting speed properly, the relevant diameter should be used in Eqs. (1.1) and (1.2) instead of d dr. For example, for reaming, counterboring, spotfacing, and tapping, this diameter is equal to the outside tool diameter. For boring, diameter d br equal to the finish diameter of the hole being bored should be used. When one deals with a multi‑stage boring tool, this diameter is equal to the largest finish diameter of the hole being bored. In countersinking, this diameter is equal to the largest diameter of the cone‑shaped enlargement at the entrance of a hole.
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 Eq. (1.1) and the given diameter as
1.2.2 Feed, Feed per tooth, and Feed r ate
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 cut ting feed, depth of cut, and uncut chip thickness commonly referred to 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.
FIGURE 1.7 Visualization of the components of the drilling regime: (a) solid drilling and (b) core drilling.
The cutting feed, f, is the distance in the direction of feed motion at which the drilling tool advances into the workpiece per one revolution, and thus, the feed is measured in millimeters per revolution (inches per revolution). The feed per tooth, fz (the subscript z came from German zahn, i.e., a tooth), is determined as
where z is the number of cutting teeth. For example, if a two‑flute drill is fed with the cutting feed f = 0.360 mm/rev, then the feed per tooth (the chip load) is f z = 0.360/2 = 0.180 mm/z; if a four‑flute reamer is fed with the cutting feed f = 0.240 mm/rev, then the feed per tooth (the chip load) is f z = 0.240/4 = 0.0 6 mm/z.
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 is calculated as
where f is the feed (mm/rev or ipm) and n is the rotational speed (rpm).
The feed speed (feed rate) is often referred to as the penetration rate in the professional literature on drilling. It is used as a measure of drilling productivity. Substituting Eq. (1.3) into Eq. (1.5) and arranging the terms, one can obtain
where k dt = 1,000/(π d dr) is a constant for a given drill.
It directly follows from Eq. (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 metal‑working fluid (MWF) (coolant) supply system.
Although Eqs. (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.
1.2.3 depth oF cUt and Material reMoval r ate
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 ap = (d drd1)/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 mm 3/min) in solid drilling is calculated as
Substituting Eq. (1.6) into Eq. (1.7), one can obtain
Referring to Figure 1.8, one can calculate MMR (measured in mm 3/min) in core drilling as
FIGURE 1.8 Visualization of the volume of the work materials removed in solid and core drilling.
1.2.4 cUt and its diMensions
Standard ISO 3002‑3 defines the cut as a layer of the workpiece material to be removed by a single action of a cutting part. It was pointed out that for a given cutting tooth, geometrical parameters of the cut are
• Nominal cross‑sectional area, AD;
• Nominal thickness, h D;
• Nominal width, bD
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
where Φp is the drilling tool point angle (discussed later in this book in Chapter 2).
The nominal width of the cut known in the literature as the uncut (undeformed) chip width is calculated as
T he nominal cross‑sectional area known in the literature as the uncut (undeformed) chip cross‑sectional area is calculated as
Substituting Eqs. (1.10) and (1.11) into Eq. (1.12), one can obtain
I n the case of core or pilot hole drilling shown in Figure 1.7b, these parameters are calculated as
T he foregoing considerations reveal that the MRR and undeformed chip cross‑sectional area do not depend on the drill point angle, while the uncut chip thickness and its width do.
Example 1.1
Problem
Determine the drill rotational speed, feed speed (the feed rate), depth of cut, MRR, 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 with a two‑flute drill (z = 2) having Φp = 120 ° if the selected cutting speed is v = 80 m/min, drill diameter is ddr = 8 mm, and feed is f = 0.15 mm/rev.
Solution
The spindle rotational speed is calculated using Eq. (1.3) as
For practical purposes, n = 3,185 rpm is adopted.
The feed speed (the feed rate) is calculated using Eq. (1.5) as vffn 0.153,185477.75 mm/min == ⋅=
The depth of cut is dw = ddr /2 = 8/2 = 4 mm.
The MRR is calculated using Eq. (1.8) as
MRRfvddr 2502500.1580 824, 000 mmmin 3 == ⋅=
The nominal thickness of cut (uncut [undeformed] chip thickness or chip load) is calculated using Eq. (1.10) as hfzDpsin2 0.15 2 sin600.065 mm. () =Φ() =° =
The nominal width of the cut (the uncut [undeformed] chip width) is calculated using Eq. (1.11) as bdDdrp 2sin 2 8 2 sin604.619 mm. () =Φ() =° =
The nominal cross‑sectional area (the uncut [undeformed] chip cross‑sectional area) is calculated using Eq. (1.12) as
AhbDDD 0.0654.6190.300 mm 2 == ⋅=
Except for some special and form tools (e.g., the tap), the discussed formulae for calculating geo metrical parameters of the cut are valid for all drilling tools. For counterboring and spotfacing, the point angle Φp = 180 ° should be used. For countersinking, these parameters vary over the cutting cycle so that the maximum nominal thickness and width of cut should be determined.
FIGURE 1.9 Boring operation.
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 Figure 1.9. The tool has Φp = 190 °, the selected cutting speed v = 240 m/min, bored hole diameter dbr = 40 mm, diameter of the hole to be bored d1 = 35 mm, and cutting feed f = 0.10 mm/rev.
Solution
The spindle rotational speed is calculated using Eq. (1.3) as
For practical purpose, n = 1,911 rpm is adopted.
The feed speed (the feed rate) is calculated using Eq. (1.5) as
mm/min.
The depth of cut is ap = (dbr d1)/2 = (40 35)/2 = 2.5 mm.
The nominal thickness of cut (uncut [undeformed] chip thickness or chip load) is calculated using Eq. (1.10) as
The nominal width of the cut (the uncut [undeformed] chip width) is calculated using Eq. (1.15) as
The nominal cross‑sectional area (the uncut [undeformed] chip cross‑sectional area) is calculated using Eq. (1.12) as
1.2.5 selecting Machining regiMe: general idea
Selecting the proper speed and feed 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 a process economy‑driven issue to achieve the system objective. 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’sHandbook , which celebrated with its 31st edition, nearly 100 years as TheBibleoftheMechanicalIndustries. The values selected in this way are always subject to specific job conditions so they were always consid ered 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 pur pose of tool layout design (discussed later in this chapter). Once the design of the whole drill ing operation is complete, and thus the parameters of the drill and drilling operation (tool holder, method of MWF supply, machine capabilities in terms of achievable speeds and feeds, etc.) have been selected, a standard or a special drill from at least two drill manufacturers should be quoted, asking them (besides the tool cost and lead time) to suggest speed and feed for the given designed operation as well as the estimation of tool life and tool reliability. If a special high‑volume opera tion is to be designed, and thus a special drilling tool is to be used, a tool manufacturer should be involved in the design of the tool layout and then the drilling tool to achieve the maximum efficiency of this operation.
Although speeds and feed rates are determined by the type of material being drilled and the depth of the hole, there are two other important system considerations to keep in mind: tool hold ing and work holding. A frequent cause of drill breakage is a loose or poorly designed tool holder that imparts wobble to the drill. Even at slow speeds and feeds, a wobble will quickly break a drill. There are many types of tool‑holding devices to choose from, but hydraulic and shrink‑fit tool hold ers provide the most secure method of tool holding, because their use results generally in the least amount of runout. A precision collet tool holder is the next best option.
Workpiece clamping is also important. If the workpiece is not clamped properly, chatter or work piece shifting due to cutting forces can be the case during drilling, which results in lower tool life, poor quality of the machined surface, and even breakage of the drill. If a drilling operation has been proceeding normally, and drills suddenly begin breaking, the first areas to check are the tool holder and the workpiece clamping.
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“Nindemann,” said the captain earnestly, “I’m sending you ahead tomorrow to get through to Ku Mark Surk for aid. It should be only twelve miles south now. You ought to do it in three days, maybe four at the most, and get back in four more. Meanwhile, we’ll follow in your trail. I’ll give you one of our two rifles, your share of the alcohol for food, and you can take any man in the party with you except Alexey to help you out. Alexey we must keep as a hunter. Who do you want?”
The quartermaster thought a moment, then answered, “I’ll take Noros, captain.”
“Isn’t Iversen better?” asked De Long anxiously. “I think he’s stronger.”
“No,” replied Nindemann, “he’s been complaining of his feet three days now.”
“That’s right, captain,” broke in Dr. Ambler who was alongside the skipper. “Noros is best.”
“All right; Noros then. Be ready, both of you in the morning.” Stiffly De Long stretched himself out before the tiny camp fire crackling feebly in the snow.
Morning found thirteen somber seamen looking anxiously off over the frozen tangle of rivers and of islands to the south. Somewhere there beyond that terrible delta land lay Ku Mark Surk and life, but all about them was only the vast snow-crusted tundra, an Arctic waste of wintry desolation and the promise of slow death. Solemnly De Long shook Nindemann’s hand.
“You’ll do all a man can do to get us help, I know, Nindemann,” he said. “God keep you safe and bring you soon again to us.”
“I ain’t got much hope of finding help, captain,” responded the quartermaster gloomily “It’s farther maybe to Ku Mark Surk than you think.”
“Well, do the best you can. If you find assistance, come back to us as quickly as possible. God knows we need it here! If you don’t—” The captain’s voice broke at that implication, he paused a moment,
then concluded huskily, “Why then you’re still as well off as we; you see the condition we are in.” He turned to Nindemann’s companion, standing in the snow beside him,
“Noros, are you ready?”
“Yes, captain.”
De Long looked them over. They carried nothing but one rifle, forty cartridges, and a small rubber bag with three ounces of alcohol, their share of the party’s sole remaining substitute for food. Their clothes were ragged, their sealskin trousers bare of fur, their boots full of holes. The captain’s eyes lingered on the toes protruding from the remnants of their footgear.
“Don’t wade in the river, men. Keep on the banks,” he finished gently.
There was a bustling in the little knot of men surrounding them, and Collins suddenly pushed through to confront De Long.
“I’m the New York Herald correspondent with this expedition,” he said bruskly. “As James Gordon Bennett’s representative, I demand the right to go with these men!”
De Long, surprised at the interruption, flushed slightly, then answered evenly,
“Mr. Collins, we’ll settle that question with Mr. Bennett in New York. At present, getting you or anybody through as a newspaper correspondent interests me very little. And in any other capacity, just now you’re only a hindrance to this expedition; you’re much too weak to keep up with Nindemann. You wouldn’t last five miles!” and turning his back on Collins, he gripped Noros’ hand, shook it warmly, and repeated,
“Remember, Noros. Keep out of the water! That’s all. Shove off now, men!”
Bending forward against the wind, Noros and Nindemann staggered away toward the south, the last forlorn hope of the eleven emaciated castaways standing in the frozen drifts behind them, cheering them as they vanished in the blinding snow.
CHAPTER XXXVII
“And that was on October 9th, Mr. Melville,” sobbed Nindemann. “But Ku Mark Surk wasn’t twelve miles away like the captain thought; it was over seventy miles! His chart was bad, and besides before, every day he hadn’t traveled so far as he guessed maybe. For ten whole days after that, Noros and me went south over terrible country, and we found to eat only one ptarmigan I shot with the rifle, and we ate up first our boot soles and then most of our sealskin pants and we froze and kept on going till even the sealskin pants was all gone and we had traveled over forty miles and still we had not come to Ku Mark Surk. And all the while we dragged ourselves along because we knew our shipmates could get no food in that country we had gone over and they were starving and the captain trusted Noros and me to get help for them.
“But after ten days we were freezing in only our underwear for clothes and we were so weak without food that we could not go on and when we saw at last an empty hut, we crawled inside there to die but we found in it a little rotten dried fish that looked like sawdust and tasted like it too and we ate that, thinking maybe then we could keep on again but the mouldy fish made us so sick with dysentery we could not even any more crawl, and we lay there three days expecting only to die soon, when at last some natives looked in that hut and found us! We would be dead there in that hut long ago if not for them!” Nindemann choked back a bitter sob and gripped my hand feebly. “We couldn’t make them natives understand they had to go back north for the captain and they brought us first to Ku Mark Surk and then here to Bulun. And now it is November 2nd, eleven more days even since they found us, and there is no hope for anybody any more! The captain and our shipmates must now all be dead in that snow!” And racked with sobs at the idea that somehow he had failed in the captain’s trust, Nindemann wept hysterically.
“Perhaps they found shelter in a hut,” I suggested, trying to calm him. “I’ll start back right now to look anyway.”
“No use,” repeated the quartermaster hopelessly “For a long ways from where we left them, there ain’t no huts, only a hundred rivers going every way and for a man twice to find the same spot there is impossible. You ain’t so strong no more. You’ll only die yourself!”
I laid the weeping seaman back on his couch. Probably he was right. But so long as the faintest shred of hope existed for Captain De Long and his comrades, I must look for them.
I got the best directions I could from Noros and from Nindemann as to the route south they had traveled, where they had stopped each night, the rivers they had crossed. Taking either man with me as a guide was impossible; they could not travel. So leaving instructions for my whaleboat party that, except for Bartlett (who was to stay in Bulun to search for me if in a month I did not return), all the others on arrival there were to proceed under Lieutenant Danenhower’s charge south to Yakutsk, I got a dog sled and immediately started north. At Ku Mark Surk I met the Russian Commandant next day; he helped me with another dog team and a ten day supply of fish. With that I proceeded northward along Nindemann’s trail from Ku Mark Surk, having two native drivers and twenty-two dogs.
Through fierce November storms we pushed on down the delta, sometimes finding Nindemann’s trail, often losing it. The going was slow, the cold was intense, we were frequently stopped by gales which completely blinded us and against which the dogs refused to travel, instead lying down in the snow and howling dolefully. The river began to divide as it spread out over the flat and treeless delta. One after another I searched along innumerable streams for Nindemann’s trail but in the deepening snows found no sign as we went north. Wrapped in thick furs, I nevertheless nearly froze to death on my sledge. It was inconceivable that De Long and his companions, long without food, clothed only in scanty rags, could live through such weather. But still I searched, hopeful now at least of recovering their bodies.
Our food gave out, the Yakut drivers wanted to return to Ku Mark Surk. I enquired if there were any village on the delta itself from which we might continue our search. They said there was one. On the far northwestern corner of the delta on the Arctic shore, some thirty miles due west of where from Nindemann’s account De Long had landed on the coast, was a small village called Tomat. I looked at my chart, a copy I had long ago made at Semenovski Island of De Long’s. There was no village marked there on that chart, but knowing now the chart to be wholly unreliable, I accepted my drivers’ statements as being true and ordered them to head for Tomat to replenish our food supply, intending then to pick up De Long’s trail at the abandoned boat, and follow him southward from there till I came upon his party, whether alive or dead. But my drivers protested; we must turn about and return to Ku Mark Surk; without food, we would all perish on the desolate road to Tomat. Fiercely I turned on them in their native tongue.
“Head north!” I ordered savagely. “And when we have to, we’ll eat the dogs! And when they’re gone, by God, I’ll eat you if necessary to get north to Tomat! Keep on north!”
Cowed by my threats, and thoroughly believing that this wild stranger from the sea might well turn cannibal, the dog drivers headed northwest toward Tomat, the solitary village on that northern Arctic coast. For three days our laboring dogs dragged us through the drifts along the road to Tomat, fortunately for us following a chain of deserted huts in each of which we found refuse scraps of fish heads, entrails of reindeer, and such similar offal, the which we (both men and dogs) ate greedily to save us from starvation, and on the fourth day, so frozen that I had to be carried from my sledge into a hut, we arrived at Tomat.
Staying there only a day to thaw out, to change my dogs for fresh ones, and to replenish my food supply (in that poor village, itself facing the winter with scanty food, getting each solitary fish was harder indeed than extracting from the villagers their teeth), I started east along the Arctic coast, with my feet so badly frozen I could not walk.
By evening, marked by a pole, I found the cache De Long had left on the beach but so thick was the falling snow I could not see the first cutter offshore. Salvaging the log books and the Jeannette’s navigating outfit, I loaded them on my sledges and turned south till I came on the first hut where De Long had stopped. For a week after, amid frigid Arctic gales with the temperature far below zero, I searched along the solidly frozen Lena, visiting every hut, finishing finally in that hut on the promontory where for three days De Long had waited for the rivers to freeze so he might cross, and where Dr. Ambler had sliced off Erichsen’s toes. There beyond the frozen river, on the wind-swept further shore, for a short distance I could follow where his toiling shipmates had dragged Erichsen along on his sledge, for the deep grooves left in the soft slush a month and a half before now stood clearly out in solid ice.
But there finally I lost the trail. The deep drifts of many snows buried all tracks. Facing a myriad of wandering streams, any one of which De Long might have followed south, I searched in vain for further tracks, for the hut in which Erichsen had finally died, for the epitaph board which Nindemann told me he had left there to mark it, but not another trace of De Long or of his party could I find in the ever-thickening snow as storm succeeded storm and buried the Lena Delta in drifts so deep that my floundering dogs could scarcely drag me through them.
It was now late November, six wintry weeks since without food and without shelter, De Long had parted somewhere thereabouts in that ghastly wilderness from his two messengers. Only one of two things now was possible—either De Long and his party had somehow been found by natives who were sheltering him, quite as safe as I myself; or he had long since perished and was somewhere buried beneath the snowdrifts on the open tundra, where in the dead of winter it was hopeless to search for him. Weak and frozen myself from my desperate search, coming on top of my long exposure in the open whaleboat, it was now imperative that I get out of the delta before my frozen corpse found an unmarked grave beneath the snows alongside my missing shipmates. So sadly I ordered my worn dogs south. It took us a week to fight our way back to Ku Mark Surk at the
delta head, and two days more to cover the final fearful miles along the Lena through the mountain gorges up to Bulun, where at last at the end of November I arrived, sick at heart at my failure to find my comrades, terribly sick physically from rotten food, from hunger, and with numbed limbs from which the Arctic cold had drained away every vestige of life.
CHAPTER XXXVIII
All winter long, while endeavoring to recuperate my frozen arms and legs, I gathered supplies and sledges from Bulun, from far-off Yakutsk, from all the villages between, for an intensive search of the delta in early March before the annual springtime freshets, feeding the Lena with the melting snows of southern Siberia, should come pouring out on the flat delta, burying it in a flood of raging waters and sweeping my shipmates out into the Arctic Sea.
I kept only Nindemann, now recovered, and Bartlett with me to help me in my search. All the remaining survivors, a pitiful party, under Lieutenant Danenhower’s charge, went south over the fifteen hundred mile trail to Irkutsk. Poor Aneguin, weakened by exposure, died before he got out of Siberia; Jack Cole, violently insane, reached America only to die soon after in a government asylum; and Danenhower himself, broken in health, after a few brief years spent undergoing a long series of operations, soon followed him to the grave. The rest except for Leach, whose toes had to be amputated, reached America safe and sound. Meanwhile by courier from Bulun to Irkutsk, the head of the telegraph lines in Siberia, the news of the disaster to the Jeannette finally went out on December 21.
For two and a half years not a word of us had ever reached civilization. As the months since our departure lengthened into years and no news came, anxiety in America and in Europe over our fate deepened into keen alarm. Swallowed by the trackless Arctic, fear for us grew, and in the summer of 1881, two relief expeditions fitted out by the American government went north to search for us. But where should they look? Which way did the polar currents go from Behring Strait where we had entered? No one knew save we on the Jeannette and our knowledge was useless to a world facing a search of the unknown north.
One expedition in the Revenue Cutter Corwin, searched for us fruitlessly off Wrangel Land but not daring to enter the ice, found no
trace. A second expedition, in the U.S.S. Alliance, thinking perhaps we might have drifted east over North America and come out beyond Greenland into the Atlantic, searched during the whole summer the fringe of the polar pack around Spitzbergen, getting in open water as far as 82° North, five degrees higher than we in the Jeannette were ever carried by the pack before it crushed us.
But neither expedition found the slightest sign of us, and more alarmed than ever, an international search was being organized by our Navy, with the help of England, Russia, and Sweden for the summer of 1882. In the midst of these preparations in late December, 1881, from far up in the Arctic Circle, my first brief telegram from Bulun at last reached Irkutsk and flashed out over the wires to an astonished world, ending the mystery of the Jeannette’s disappearance, bringing joy to some whose friends had definitely escaped; blank despair to others whose lives were bound up with poor Chipp and his lost boat’s crew; and a terrible state of mingled fear and hope, not to be resolved for unknown months yet, to Emma De Long and the families of those men still with her husband. I felt that they were dead, but I did not know it, and dared not say so. I could only announce them as having landed safely, but yet unfound. My heart ached for Emma De Long, half the globe away from me, clinging to her daughter, praying that her husband might yet be alive, tortured by the long drawn out fear of waiting for word from Siberia, dreading each knock at the door as announcing the messenger bringing definitely the black news of his death, and all the while with her imagination able to dwell only on the agonies which her husband had undergone, and if by some miracle (for which she prayed) he still were living among those Arctic wastes, he must yet be suffering.
I received carte blanche from Washington for funds to pursue the search; from St. Petersburg, I was assured all the resources of Russia were at my command. But Washington and St. Petersburg were far away from the trackless delta where I must pursue my search, and carte blanche telegrams helped me little. A few dogs, a few interpreters, a supply of dried fish sold under compulsion by natives who could ill afford to spare them, was the total extent of the assistance I could use and get delivered to distant Bulun up in the
Arctic Circle, fifteen hundred long miles away from civilization and the telegraph wires at Irkutsk, when in late February with practically all the fish in the Lena Delta in my possession and the poor Yakuts face to face with famine, I resumed my search.
Dividing my forces, I sent Bartlett and an interpreter to cover the eastern branches of the Lena, while with Nindemann to guide me, I started again to search the western branches myself.
I had seven dog teams hauling fish, having practically stripped Jamaveloch and every Lena village of its entire supply. Delayed considerably still by fierce snow storms, we went north from Ku Mark Surk into the delta, but it took two weeks for the straining dogs to drag our stores along to where the Lena started branching widely at Cass Carta, and many a burdened dog froze to death in the drifts before he got there. At Cass Carta at last, I reorganized my remaining teams and on March 12, still in the midst of-winter weather, sent Bartlett east, and with Nindemann, began myself the search of western rivers.
For a week, systematically Nindemann scouted along each river, trying to pick out the one that he and Noros had followed south. But the innumerable storms since had changed the whole face of that frozen country How many streams we examined, I cannot even guess. Nindemann, his broad brows knit with puzzled furrows, could find nothing familiar in any of them. Baffled, we gave up searching there and went far to the north, to follow down De Long’s trail from the coast, but at the same point where in November I had lost the track, Nindemann himself was able to do no better in pointing out the path. And then came a raging storm which held us snowbound for three days.
Despairingly I considered the situation. Would we ever pick up De Long’s track? It must be soon or never! Before long the river ice would break up, we could no longer travel, and swollen with melting snow from the whole interior of Siberia, the Lena would come flooding down in torrents to drown out the low delta lands, washing away forever every trace of my comrades! De Long must be somewhere to the south. In desperation, I gave up searching the
central delta for his track, and decided to go back again to the delta head, to sweep the spreading rivers there as I came north.
Soon after, starting from the southward again, since Nindemann also felt that there he could do best, we began at a wide bay, from which one tremendous river flowed eastward toward Jamaveloch, another flowed westward and northward toward Tomat, and in between the Lena, in many smaller branches, flowed due north, spreading widely out and meandering over the delta, though now of course it flowed beneath the ice as every stream was still solidly frozen over.
Following the edge of this tremendous bay, I examined every headland on it. Broken slabs of ice were piled up in tangled masses on the banks; the snow, drifted by the winds, ran in smooth slopes from the river ice to the tops of the promontories, filling in the banks; dozens of frozen streams, like twigs spreading from a limb, branched out from the bay, complicating the search.
Coming in the late afternoon to a high headland on the western side of the bay, I left my sledge as usual on the river ice, and clambered up the crust of snow to its top. The crest was strongly wind-swept and fairly bare of snow; as I stooped to brace myself against the wind, I saw right on the point of the promontory signs of a long-dead fire, with half-burned driftwood logs hove into the wide bed of ashes and apparently many footprints in the ice about.
Beckoning to Nindemann to come up, I asked him,
“Did you or Noros build that fire here?”
“No,” said Nindemann, “it looks to me we came this way, but we never had a fire like that.”
I motioned up my dog-driver, questioned him in native dialect,
“Do Yakuts build fires this way?”
“No, no, master,” he protested volubly, “Yakuts build only small fires, never big fires like this.”
“Well, Nindemann,” I said, “I think we’re on the trail at last. This looks to me like a signal fire, especially since it’s built on this
promontory to shine out over the bay De Long must have passed here.”
“Yah,” agreed the quartermaster, “that is right. There! See? There is the old wreck of a flatboat on the bank and I remember Louis and me passed by that wreck the same day we left the captain! This is the way we came, and the captain said he’d follow our trail!”
Going down to the river again, we climbed aboard our dog sledges. Nindemann on his sledge led along the ice, and with me following on mine, we set off on a short journey up the stream to examine the bare skeleton of that flatboat, stranded on the bank a quarter of a mile downstream.
I rode, sitting sideways on my sledge, facing the high bank which rose some thirty feet above the river, and which, as usual, had harddriven snow packed in a glistening slope from its crest down over the frozen river. Going swiftly along over the ice this way while eagerly scanning the river bank, I noted standing up through the sloping snow what seemed to be the points of four sticks lashed together with a rope.
Immediately I rolled off the speeding sledge, and swiftly going to the spot, found a Remington rifle slung from the sticks, its muzzle some eight inches out of the snow. A real sign of De Long at last!
Instantly I sent my driver to bring Nindemann back, feeling that here the weakening wanderers might have made a cache of such belongings as they could no longer carry, and perhaps even have left a record of their progress. We were certainly on the trail now!
While the Yakuts at my orders began digging in the snow around those sticks, Nindemann returned to the flatboat, and I with a compass again climbed up the steep river bank, intending to get some bearings from which later I might find that spot in case a sudden snow-storm should blot out the way to it.
Panting from my exertions, I looked about for a good place on that high ground from which to take the compass bearings when a few steps off, partially buried in the snow still left on that forlorn and galeswept height, I saw a copper tea kettle. With a beating heart, I
started for it, then stopped short. There before me on that desolate plateau, protruding stiff and stark above the snow—was an extended arm!
L D
For an instant I gazed, aghast at my discovery, then dropped to my knees to find that that arm belonged to Captain De Long! There he lay, cold and silent in death, half buried in the snow. A yard or two off lay Dr. Ambler, while near their feet, closest to where the fire had been beneath the copper kettle, was stretched Ah Sam. My long search was ended at last!
Mournfully I looked. There had the saga of the Jeannette ended, there in the Arctic snows was my lost captain—dead. For a long time with bowed head, I knelt sobbing before my commander, whom last I had seen, erect in the cockpit of his boat in the midst of that roaring polar gale which had brought swift death to Chipp, waving me on to safety.
As I gazed tear-stricken into his face, calm even in death, I was struck by the odd position of his left arm, upraised with open fingers as if, lying there dying, he had tossed something over his shoulder and his stiffening arm had frozen in that gesture. I looked behind him.
A few feet away in the snow beyond his head lay a small notebook, the journal he had kept since the Jeannette sank. To me it seemed as if De Long, in his dying moment had tossed that journal over his head, away from the fire at his feet lest it should blow in there and be destroyed. I seized the journal and rose. Before me were only three of the captain’s party—where were the other eight? Perhaps the journal, if the dying captain had kept it up, might tell me. Nindemann had parted from the captain on October 9. What had happened since that day? Hurriedly, I separated the frozen leaves and turned to the page marked—
CHAPTER XXXIX
“October 10th, Monday—120th day.
Last half ounce alcohol at 5:30; at 6:30 send Alexey off to look for ptarmigan. Eat deerskin scraps. Yesterday morning ate my deerskin footnips. Light S.S.E. airs. Not very cold. Under way at eight. In crossing creek three of us got wet. Built fire and dried out. Ahead again until eleven. Used up. Built fire. Made a drink out of the tealeaves from alcohol bottle. On again at noon. Fresh S.S.W. wind, drifting snow, very hard going. Lee begging to be left. Some little beach, and then stretches of high bank. Ptarmigan tracks plentiful. Following Nindemann’s tracks. At three halted, used up; crawled into a hole in the bank, collected wood and built fire. Alexey away in quest of game. Nothing for supper except a spoonful of glycerine. All hands weak and feeble, but cheerful. God help us.
October 11th, Tuesday—121st day.
S.W. gale with snow. Unable to move. No game. One spoonful of glycerine and hot water for food. No wood in our vicinity.
October 12th, Wednesday—122nd day.
Breakfast; last spoonful of glycerine and hot water. For dinner, we tried a couple of handfuls of Arctic willow in a pot of water and drank the infusion. Everybody getting weaker and weaker. Hardly strength to get firewood. S.W. gale with snow.
October 13th, Thursday—123rd day
Willow tea. Strong S.W. wind. No news from Nindemann. We are in the hands of God, and unless He intervenes, we are lost. We cannot move against the wind, and staying here means starvation. Afternoon went ahead for a mile, crossing either another river or a bend in the big one. After crossing missed Lee. Went down in a hole in the bank and camped. Sent back for Lee. He had turned back, lain down, and was waiting to die. All united in saying Lord’s Prayer and Creed after supper. Living gale of wind. Horrible night.
October 14th, Friday—124th day
Breakfast, willow tea. Dinner, one half teaspoonful sweet oil and willow tea. Alexey shot one ptarmigan; had soup. S.W. wind moderating.
October 15th, Saturday—125th day.
Breakfast, willow tea and two old boots. Conclude to move on at sunrise. Alexey breaks down, also Lee. Come to empty grain raft. Halt and camp. Signs of smoke at twilight to southward.
October 16th, Sunday—126th day.
Alexey broken down. Divine Service.
October 17th, Monday—127th day.
Alexey dying. Doctor baptized him. Read prayers for sick. Mr Collins’ birthday; forty years old. About sunset Alexey died; exhaustion from starvation. Covered him with ensign and laid him in the crib.
October 18th, Tuesday—128th day.
Calm and mild, snow falling. Buried Alexey in the afternoon. Laid him on the ice of the river and covered him with slabs of ice.
October 19th, Wednesday—129th day
Cutting up tent to make footgear. Doctor went ahead to find new camp. Shifted by dark.
October 20th, Thursday—130th day.
Bright and sunny, but very cold. Lee and Kaack done up.
October 21, Friday—131st day.
Kaack was found dead about midnight between the Doctor and myself. Lee died about noon. Read prayers for sick when he found he was going.
October 22nd, Saturday—132nd day
Too weak to carry the bodies of Lee and Kaack out on the ice. The Doctor, Collins and I carried them around the corner out of sight. Then my eye closed up.
October 23rd, Sunday—133rd day.
Everybody pretty weak. Slept or rested all day and then managed to get enough wood in before dark. Read part of Divine Service. Suffering in our feet. No footgear.
October 24th, Monday—134th day
A hard night.
October 25th, Tuesday—135th day.
October 26th, Wednesday—136th day.
October 27th, Thursday—137th day. Iveson broken down.
October 28th, Friday—138th day.
Iveson died during early morning.
Oct. 29th, Saturday—139th day.
Dressier died during night.
Oct. 30. Sunday, 140th day.
Boyd and Görtz died during night. Mr. Collins dying
