Design Improvement Of Wheel Spacer.
UNIVERSITI TEKNIKAL MALAYSIA MELAKA
Design Improvement of Wheel Spacer
Thesis submitted in accordance with the partial requirements of the Universiti Teknikal Malaysia Melaka for the
Bachelor of Manufacturing Engineering (Manufacturing Process)
By
Tan Soon Lam
Faculty of Manufacturing Engineering March 2008
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DESIGN IMPROVEMENT OF WHEEL SPACER
TAN SOON LAM
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UNIVERSITI TEKNIKAL MALAYSIA MELAKA
BORANG PENGESAHAN STATUS TESIS*
JUDUL: _______________________________________________________________ _______________________________________________________________ _______________________________________________________________ SESI PENGAJIAN : _______________________
Saya _____________________________________________________________________
mengaku membenarkan t esis (PSM/ Sarj ana/ Dokt or Falsaf ah) ini disimpan di Perpust akaan Universit i Teknikal Malaysia Melaka (UTeM) dengan syarat -syarat kegunaan sepert i berikut :
1. Tesis adalah hak milik Universit i Teknikal Malaysia Melaka .
2. Perpust akaan Universit i Teknikal Malaysia Melaka dibenarkan membuat salinan unt uk t uj uan pengaj ian sahaj a.
3. Perpust akaan dibenarkan membuat salinan t esis ini sebagai bahan pert ukaran ant ara inst it usi pengaj ian t inggi.
4. **Sila t andakan (√)
(HURUF BESAR)
SULIT
TERHAD
TIDAK TERHAD
(Mengandungi maklumat yang berdarj ah keselamat an at au kepent ingan Malaysia yang t ermakt ub di dalam AKTA RAHSIA RASMI 1972)
(Mengandungi maklumat TERHAD yang t elah dit ent ukan oleh organisasi/ badan di mana penyelidikan dij alankan)
(TANDATANGAN PENULIS) Alamat Tet ap:
Tarikh: _______________________
Disahkan oleh:
(TANDATANGAN PENYELIA) Cop Rasmi:
Tarikh: _______________________
* Tesis dimaksudkan sebagai t esis bagi Ij azah Dokt or Falsaf ah dan Sarj ana secara penyel idikan, at au disert asi bagi pengaj ian secara kerj a kursus dan penyel idikan, at au Laporan Proj ek Sarj ana Muda (PSM). ** Jika t esis ini SULIT at au TERHAD, sil a l ampirkan surat daripada pihak berkuasa/ organisasi berkenaan dengan menyat akan sekali sebab dan t empoh t esis ini perl u dikel askan sebagai SULIT at au TERHAD.
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FAKULTI KEJURUTERAAN PEMBUATAN
Rujukan Kami (Our Ref) : 17 March 2008 Rujukan Tuan (Your Ref):
Pust akawan
Perpust akawan Universit i Teknikal Malaysia Melaka UTEM, Ayer Keroh
MELAKA. Saudara,
PENGKELASAN TESIS SEBAGAI SULIT/ TERHAD
- TESIS SARJANA MUDA KEJURUTERAAN PEMBUATAN (PROSES PEMBUATAN): TAN SOON LAM
TAJUK: DESIGN IMPROVEMENT OF WHEEL SPACER
Sukacit a dimaklumkan bahawa t esis yang t ersebut di at as bert aj uk “ Design
improvement of wheel spacer ” mohon dikelaskan sebagai t erhad unt uk
t empoh lima (5) t ahun dari t arikh surat ini memandangkan ia mempunyai nilai dan pot ensi unt uk dikomersialkan di masa hadapan.
Sekian dimaklumkan. Terima kasih.
“ BERKHIDMAT UNTUK NEGARA KERANA ALLAH”
Yang benar,
WAN HASRULNIZZAM WAN MAHMOOD
Pensyar ah,
Fakul t i Kej ur ut er aan Pembuat an (Penyel i a Ber sama)
06-2332122
UNIVERSITI TEKNIKAL MALAYSIA MELAKA Karung Berkunci 1200, Ayer Keroh, 75450 Melaka
Tel : 06-233 2421, Faks : 06 233 2414 Email : fkp@kutkm.edu.my
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DECLARATION
I hereby, declared this thesis entitled “Desi gn i mpr ovement of wheel spacer” was the results of my own research except as cited in references.
Signature : ……….
Author’s Name : Tan Soon Lam
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ABSTRACT
This project focused on the problems of existing wheel spacer design thus developing new designs to eliminate these problems. Based on the scoring concept wheel spacer with the slotting design was chosen as the new design. Document control of wheel spacer was developed with the proper fabrication flow chart, production tooling and computer drawing. Special fixture of milling machine was developed to match the wheel spacer with slotting design. Problems and observation of the wheel spacer fabrication were among the matters discussed in this report. Comparisons were made for both the new and existing design of wheel spacer. From the machine design calculation, the clamping force and tensile stress area for the wheel spacer were 0.0055 inch2 and 10170 lb. Finally the destructive testing of new design was done to ensure the existing problems were eliminated.
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ABSTRAK
Projek ini memfokuskan masalah pada rekabentuk Pelapis Roda yang ada di pasaran dan rekabentuk baru dipertingkatkan untuk menyelesaikan masalah ini. Berdasarkan konsep skoring, rekabentuk slot dipilih sebagai rekabentuk yang baru. Dokumen kawalan dibangunkan dengan arus pembuatan, peralatan dan lukisan kejuruteraan roda pelapis. Rekabentuk lama dibandingkan yang baru dan dinilai hasilnya. Daripada, mesin rekabentuk pengiraan, daya pengapit dan daya tegangan permukaan ialah 0.0055 inch2 dan 10170 paun. Akhir sekali, percubaan musnah dilakukan bagi memastikan masalah rekabentuk lama diselesaikan.
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DEDICATION
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ACKNOWLEDGEMENT
A debt of gratitude to my talented supervisor, Mr. Taufik for his high dedication, advises and superb guidance, which prepared me in overcoming the challenges in this final year project. I would also like to thank take this opportunity to thank to all those have been involved in making this project a successes. And finally, a warm thanks to the technician in D.Cam Automotive Accessories for his helping hand to fabricate the wheel spacer.
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TABLE OF CONTENTS
Abstract………...i
Abstrak………...ii
Dedication………....iii
Acknowledgement………...iv
Table of Contents……….………v
List of Tables………..…...viii
List of Figures………..ix
List of abbreviations, symbols, specialized ………...….xi
1. INTRODUCTION………….………1
1.1Background………...1
1.2Problem statements……….………..2
1.3Objective of the Project……….………...………2
1.4Scope of Project……….………...…2
1.5Schematic of Project……….………3
2. LITERATURES REVIEW……….……….…....4
2.1Introduction………..….…4
2.2Wheel Spacer………..……..4
2.3Manufacturing Process………..…...5
2.3.1 Lathe Operation………..…..5
2.3.2 Milling Operation ……….………...6
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vi
2.4Fastener………7
2.4.1 Thread Designations………..………..7
2.4.2 Performance of Bolted Joints………..…………8
2.5D Cam Auto Accessories………9
3. METHODOLGY ………..………..….11
3.1 Introduction……….………...…11
3.2Generic Product Development Processes………...…11
3.3Limitations of the Project……….…...12
4. DESIGN FABRICATION AND ASSEMBLY WHEEL SPACER……..…...14
4.1Introduction………...…..14
4.2Concept Development and System Level of wheel spacer ……….…….…..14
4.2.1 Sketch of Wheel Spacer………..…14
4.2.2 Process Flow Chart of Final Assembly Process………….…………17
4.3Detail Design of Wheel Spacer……….……….………18
4.3.1 Computer Drawing……….18
4.3.2 Production Tooling……….30
4.3.3 Process Plan for fabrication………..….….31
4.3.4 Assembly of Product………..34
4.4Destructive Testing of Wheel spacer.……….38
4.5Wheel Spacer Measurement………...…41
5. DISCUSSION………...43
5.1Introduction……….……43
5.2Design Requirement……….,…..43
5.3Concept Scoring………...44
5.4Machine Design Calculation………...46
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5.6Wheel Spacer Specification………...….49
6. CONCLUSION AND RECOMMEDATION………50
6.1 Conclusion………..…….…..50
6.2 Recommendation……….…...….51
REFERENCES ……….………...52
APPENDICES
A Application letter to Cameleon Auto Machining B GSK Drilling and Milling Machine specification
C Questionnaire on the design of the Wheel Spacer D G-code for Drilling
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viii
LIST OF TABLES
4.1 Cutting Tool and Process Parameter 30
4.2 Sequence of the Wheel Spacer fabrication 31 4.3 Comparison of Existing Design and New Design 37
5.1 Concept scoring for wheel spacer design 43
5.2 Wheel stud specification 49
5.2 Spacer specification 49
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ix
LIST OF FIGURES
2.1 The D Cam Automotive Accessories Factory. 9 2.2 The D Cam Automotive factory at lathe department. 10 2.3 The D Cam Automotive factory at milling department. 10
3.1 Generic Product Development Processes 13
4.1 Concept Design of Wheel Spacer using welding process 15 4.2 Concept Design of Wheel Spacer using End Mills process 15 4.3 Comparison of original and new design of wheel stud 16
4.4 Fixture to End Mills Wheel stud Head 16
4.5 Flowchart of Wheel Spacer fabrication 17
4.6 Solid Modeling of the Wheel Spacer 19
4.7 Solid Modeling of the Spacer 19
4.8 Solid Modeling of the Wheel stud 20
4.9 Solid Modeling of the nut 20
4.10 3D of Wheel spacer 21
4.11 Overall View of the Spacer 22
4.12 Isometric View of the Spacer 23
4.13 Bottom View of the Spacer 24
4.14 Bottom View of the Spacer 25
4.15 Side View of the Spacer 26
4.16 Coordinate of the holes for spacer 27
4.17 View of wheel stud 28
4.18 View of the Nut 29
4.19 Drilling and Milling Machine 33
4.20 Special Fixture to End mill the Wheel stud 33
4.21 Hydraulic machine 34
4.22 Press in wheel Stud into spacer 34
4.23 Isometric view of the complete Assembly of the Wheel spacer 35 4.24 Front view of complete Assembly of the Wheel spacer 35
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4.25 Back view of complete Assembly of the Wheel spacer 36
4.26 Wheel Stud with new design 36
4.27 Impact Wrench 38
4.28 Impact Wrench to tighten the nut 38
4.29 Destructive Testing on Wheel Spacer 39
4.30 Stress distribution in the wheel spacer 40
4.31 Calibration of surface roughness machine. 41 4.32 Measurement of wheel spacer surface roughness 41
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LIST OF ABBREVIATIONS, SYMBOLS, SPECIALIZED
NOMENCLATURE
CNC – Computer Numerical Computer G-Code – Programming language
HSS – High speed Steel Ib.in – Pound per inch
M – Major Diameter for thread MM/MIN – Millimeter per minute
P - Pitch
PCD – Pitch Circle Diameter
PLC – Programmable Logic Controller Ra – Surface roughness
Rev /min – Revolution per minute T6 – Heat Treated
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CHAPTER 1
INTRODUCTION
1.1 Background
According to Alloy Spacer Germany (2007), Wheel spacers move the wheel out from the hub, effectively widening the stance of the vehicle and lowering its roll centre. This simple modification increases lateral stability, which in turn provides improved handling, greater safety and of course, the sleek style you’ve been looking for. Depending on vehicle make and model they are available for most domestic and imported automobiles.
Wheel spacers are also used when a cars such as: Nissan 240SX, 350Z / GTO, Peugeot 406's or some Alfa Romeo's (to name a few) have upgraded brakes, and want to fit aftermarket alloy wheels on, but the larger brake calipers prevents this by coming into contact with the alloy wheel. Other customers needs wheel spacers when they have used brake upgrade kits such as Brembo, Stop-Tech, Endless and other brake kits. Consumers need Professional knowledgeable company when purchasing alloy wheel spacers.
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2 1.2 Problem Statement
There are different types sport wheel available in the market. But the original wheel hub cannot fit with the sport wheel. So the spacer wheel is manufactured to move the wheel out from the hub, effectively widening the stance of the vehicle and lowering its roll centre. Besides that, the wheel stud used to tighten the wheel spacer and sport wheel is easily getting loose when over force is applied on the wheel stud. As a result, the wheel stud cannot clamp the sport wheel effectively.
1.3 Objective
1) To improve existing design of the wheel spacer.
2) To fabricate and assembly of new design automotive wheel spacer.
3) To analyze automotive wheel spacer.
1.4 Scope of the Project
Propose a new design of wheel spacer which prevents screw of wheel spacer from easily getting loose. Describe and fabricate new design of spacer wheel with and Lathe machine and Computer Numerical Control (CNC) Milling. Destructive testing will be performed in this project. Besides that, the basic analysis of wheel spacer such as Clamping force and tensile stress area are included in this project. All this values are approximated.
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3 1.5 Schematic of Project
Chapter 1 describes about the background of the study, project problem statement, and the objective and scope of the project.
Chapter 2 highlights some literature reviews related to the study, which includes descriptions on Design Wheel Spacer, Manufacturing Process of wheel spacer and Fastener to clamp the wheel spacer. Besides that, it describes the Concept Scoring for product design and development.
Chapter 3 shows the methodology of the Wheel Spacer project in details. This chapter explains how to develop the wheel spacer with generic product development process. This chapter also includes limitations of the project.
Chapter 4 shows details design such as computer drawing, production tooling, process plan for fabrication and assembly. It also shows existing design and new design of the wheel spacer.
Chapter 5 provides explanation on the design requirements for the wheel spacer. Besides that, this chapter also illustrates the concept scoring for the wheel spacer which determines the final of choice design to fabricate. Moreover, some analysis of the clamping force and tensile area of thread of wheel spacer are calculated.
Chapter 6 makes a conclusion on the project where the best designs were chosen. Recommendations are included in this chapter as well.
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CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
Chapter 2 described overall of the wheel spacer which include wheel stud, material, design and manufacturing method to process wheel spacer. Besides that, it also theory shows machine design calculation for clamping force and tensile area for bolts and nut.
2.2 Wheel Spacer
From the clarification explanation of Wikipedia(2008), Wheel studs are the bolts that the wheel of an automobile rest on. Lug nuts are fastened to the wheel stud to secure the wheel. Wheel studs can be either factory equipment or aftermarket add-ons. They are semi-permanently mounted directly to the vehicle brake drum or disk hub.
The primary advantage of wheel studs over wheel bolts is greater strength due to an increase in clamping force and resistance to loosening. Another benefit is greater ease for tire changes by creating the ability to lift both the wheel and tire onto the studs creating the ability to hold and locate the assembly during tire changes rather than trying to hold up the wheel and tire while lining up the holes to insert a bolt.
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Wheel studs are replaceable and come in two basic kinds: press-in and screw-in. Welded-in studs are possible but unlikely to be encountered. Screw-in studs simply screw into the existing threaded bolt hole in the hub. The end that screws into the hub is usually either threaded with a higher tolerance fit or installed with a chemical thread locking compound to keep it from backing out from the hub when the lug nut is removed
Press-in studs are installed from the back side of the disk or drum hub and require removal of the hub from the vehicle for installation or removal. They consist of a threaded portion and a larger diameter section that is splined to prevent rotation. The diameter of the splined section is larger than the hole in the hub requiring a press fit to seat the stud. The stud is prevented from being pulled through the hub by a larger diameter stop on the end.
Most press-in studs are designed and recommended to be installed with a mechanical or hydraulic press to ensure proper seating without damage. It is possible, though not advised, to install a press-in by using a washer and nut to "draw" it into the hub. In doing so, the installer must ensure that the stud is fully seated and that no damage is done to the threaded portion of the stud.
2.3 Manufacturing Process
2.3.1 Lathe Operation
From the explanation of Wikipedia (2008), turning is process in machine tool which spins a block of material so that when abrasive, cutting, or deformation tools are applied to the workpiece, it can be shaped to produce an object which has rotational symmetry about an axis of rotation, called Solids of Revolution. Examples of objects that can be produced on a lathe include candlestick holders, table legs, bowls, baseball bats, crankshafts or camshafts.
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The material may be held in place by a chuck or worked between one or two centers of which at least one can be moved horizontally to accommodate varying material lengths. In a metalworking lathe, metal is removed from the workpiece using a hardened cutting tool which is usually fixed to a solid moveable mounting called the "toolpost", this arrangement is then moved around the workpiece using handwheels and/or computer controlled motors. The main difference between the Milling Machine and the Lathe is that in the Milling Machine the tool is moving but in the Lathe, the work is moving. Modern CNC lathes can do secondary operations like milling in X,Y,Z direction by using driven tools also called live tools. When driven tools are used the work piece stops rotating and the driven tool executes the machining operation with a rotating cutting tool. Driven tools increase machining performance as all operations can be made in one set up in the CNC lathe
2.3.2 Milling Operation
From the explanation of Wikipedia(2008), Milling is the complex shaping of metal (or possibly other materials) parts, by removing unneeded material to form the final shape. It is generally done on a milling machine, a power-driven machine that in its basic form is comprised of a milling cutter that rotates about the spindle axis (like a drill), and a worktable that can move in multiple directions (usually three dimensions [x,y,z axis] relative to the workpiece, whereas a drill can only move in one dimension [z axis] while cutting). The motion across the surface of the workpiece is usually accomplished by moving the table on which the workpiece is mounted, in the x and y directions. Milling machines may be operated manually or under computer numerical control (CNC), and can perform a vast number of complex operations, such as slot cutting, planing, drilling and threading, rabbeting, routing, etc. Two common types of millers are the horizontal miller and vertical miller.
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7 2.3.4 Drilling Operation
From the explanation of Wikipedia (2008), Drilling is the process of using a drill bit in a drill to produce holes. Under normal usage, swarf is carried up and away from the tip of the drill bit by the fluting. The continued production of chips from the cutting edges pushes the older chips outwards from the hole. This continues until the chips pack too tightly, either because of deeper than normal holes or insufficient backing off (removing the drill slightly [breaking the chip] or totally from the hole [clearing the bit] while drilling). Lubricants (or coolants) (i.e. cutting fluid) are sometimes used to ease this problem and to prolong the tool's life by cooling, lubricating the tip and improving chip flow.
Taps and dies are tools commonly used for the cutting of screw threads in metal parts. A tap is used to cut a female thread on the inside surface of a predrilled hole, while a die cuts a male thread on a preformed cylindrical rod.
2.4 Fastener
2.4.1 Thread Designations
According to Mott (1999), the formula for tensile stress area is At = (0.7854) (D-0.974 2p)
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8 2.4.2 Performance of Bolted Joints
Besides that, Mott (1999) also provide the Tightening Torque formula
T =KDP
Where T = torque, Ib.in
D = Nominal Diameter of threads, in P = Clamping load, Ib
K = Constant Dependent on the lubrication present, where K =0.15 and K =2.0 if the threads cleaned and dried
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3 1.5 Schematic of Project
Chapter 1 describes about the background of the study, project problem statement, and the objective and scope of the project.
Chapter 2 highlights some literature reviews related to the study, which includes descriptions on Design Wheel Spacer, Manufacturing Process of wheel spacer and Fastener to clamp the wheel spacer. Besides that, it describes the Concept Scoring for product design and development.
Chapter 3 shows the methodology of the Wheel Spacer project in details. This chapter explains how to develop the wheel spacer with generic product development process. This chapter also includes limitations of the project.
Chapter 4 shows details design such as computer drawing, production tooling, process plan for fabrication and assembly. It also shows existing design and new design of the wheel spacer.
Chapter 5 provides explanation on the design requirements for the wheel spacer. Besides that, this chapter also illustrates the concept scoring for the wheel spacer which determines the final of choice design to fabricate. Moreover, some analysis of the clamping force and tensile area of thread of wheel spacer are calculated.
Chapter 6 makes a conclusion on the project where the best designs were chosen. Recommendations are included in this chapter as well.
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4
CHAPTER 2
LITERATURE REVIEW
2.1 Introduction
Chapter 2 described overall of the wheel spacer which include wheel stud, material, design and manufacturing method to process wheel spacer. Besides that, it also theory shows machine design calculation for clamping force and tensile area for bolts and nut.
2.2 Wheel Spacer
From the clarification explanation of Wikipedia(2008), Wheel studs are the bolts that the wheel of an automobile rest on. Lug nuts are fastened to the wheel stud to secure the wheel. Wheel studs can be either factory equipment or aftermarket add-ons. They are semi-permanently mounted directly to the vehicle brake drum or disk hub.
The primary advantage of wheel studs over wheel bolts is greater strength due to an increase in clamping force and resistance to loosening. Another benefit is greater ease for tire changes by creating the ability to lift both the wheel and tire onto the studs creating the ability to hold and locate the assembly during tire changes rather than trying to hold up the wheel and tire while lining up the holes to insert a bolt.
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5
Wheel studs are replaceable and come in two basic kinds: press-in and screw-in. Welded-in studs are possible but unlikely to be encountered. Screw-in studs simply screw into the existing threaded bolt hole in the hub. The end that screws into the hub is usually either threaded with a higher tolerance fit or installed with a chemical thread locking compound to keep it from backing out from the hub when the lug nut is removed
Press-in studs are installed from the back side of the disk or drum hub and require removal of the hub from the vehicle for installation or removal. They consist of a threaded portion and a larger diameter section that is splined to prevent rotation. The diameter of the splined section is larger than the hole in the hub requiring a press fit to seat the stud. The stud is prevented from being pulled through the hub by a larger diameter stop on the end.
Most press-in studs are designed and recommended to be installed with a mechanical or hydraulic press to ensure proper seating without damage. It is possible, though not advised, to install a press-in by using a washer and nut to "draw" it into the hub. In doing so, the installer must ensure that the stud is fully seated and that no damage is done to the threaded portion of the stud.
2.3 Manufacturing Process
2.3.1 Lathe Operation
From the explanation of Wikipedia (2008), turning is process in machine tool which spins a block of material so that when abrasive, cutting, or deformation tools are applied to the workpiece, it can be shaped to produce an object which has rotational symmetry about an axis of rotation, called Solids of Revolution. Examples of objects that can be produced on a lathe include candlestick holders, table legs, bowls, baseball bats, crankshafts or camshafts.
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6
The material may be held in place by a chuck or worked between one or two centers of which at least one can be moved horizontally to accommodate varying material lengths. In a metalworking lathe, metal is removed from the workpiece using a hardened cutting tool which is usually fixed to a solid moveable mounting called the "toolpost", this arrangement is then moved around the workpiece using handwheels and/or computer controlled motors. The main difference between the Milling Machine and the Lathe is that in the Milling Machine the tool is moving but in the Lathe, the work is moving. Modern CNC lathes can do secondary operations like milling in X,Y,Z direction by using driven tools also called live tools. When driven tools are used the work piece stops rotating and the driven tool executes the machining operation with a rotating cutting tool. Driven tools increase machining performance as all operations can be made in one set up in the CNC lathe
2.3.2 Milling Operation
From the explanation of Wikipedia(2008), Milling is the complex shaping of metal (or possibly other materials) parts, by removing unneeded material to form the final shape. It is generally done on a milling machine, a power-driven machine that in its basic form is comprised of a milling cutter that rotates about the spindle axis (like a drill), and a worktable that can move in multiple directions (usually three dimensions [x,y,z axis] relative to the workpiece, whereas a drill can only move in one dimension [z axis] while cutting). The motion across the surface of the workpiece is usually accomplished by moving the table on which the workpiece is mounted, in the x and y directions. Milling machines may be operated manually or under computer numerical control (CNC), and can perform a vast number of complex operations, such as slot cutting, planing, drilling and threading, rabbeting, routing, etc. Two common types of millers are the horizontal miller and vertical miller.
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7 2.3.4 Drilling Operation
From the explanation of Wikipedia (2008), Drilling is the process of using a drill bit in a drill to produce holes. Under normal usage, swarf is carried up and away from the tip of the drill bit by the fluting. The continued production of chips from the cutting edges pushes the older chips outwards from the hole. This continues until the chips pack too tightly, either because of deeper than normal holes or insufficient backing off (removing the drill slightly [breaking the chip] or totally from the hole [clearing the bit] while drilling). Lubricants (or coolants) (i.e. cutting fluid) are sometimes used to ease this problem and to prolong the tool's life by cooling, lubricating the tip and improving chip flow.
Taps and dies are tools commonly used for the cutting of screw threads in metal parts. A tap is used to cut a female thread on the inside surface of a predrilled hole, while a die cuts a male thread on a preformed cylindrical rod.
2.4 Fastener
2.4.1 Thread Designations
According to Mott (1999), the formula for tensile stress area is At = (0.7854) (D-0.974 2p)
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8 2.4.2 Performance of Bolted Joints
Besides that, Mott (1999) also provide the Tightening Torque formula
T =KDP
Where T = torque, Ib.in
D = Nominal Diameter of threads, in P = Clamping load, Ib
K = Constant Dependent on the lubrication present, where K =0.15 and K =2.0 if the threads cleaned and dried