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The Formation and Properties of Machining Burrs

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The Formation and Properties of Machining Burrs Utah State University DigitalCommons@USU All Graduate Theses and Dissertations Graduate Studies 5-1973 The Formation and Properties of Machining Burrs LaRoux K. Gillespie Utah State University Follow this and additional works at: https://digitalcommons.usu.edu/etd Part of the Manufacturing Commons Recommended Citation Gillespie, LaRoux K., "The Formation and Properties of Machining Burrs" (1973). All Graduate Theses and Dissertations. 4558. https://digitalcommons.usu.edu/etd/4558 This Thesis is brought to you for free and open access by the Graduate Studies at DigitalCommons@USU. It has been accepted for inclusion in All Graduate Theses and Dissertations by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. ii ACJ<NO W LE DG ME NTS This study of Burr Formation is an outgrowth of the author's earlier work on Deburring Procpsses. In studying the techniques re- quired for ren1oving burrs fron1 precision 1nin i aturf' components two important conside rations became obvious: a) For repeatible deburring the bun· properties have to be repeatible and b) A knowledge of how burrs forrn is essential if one wishes to predict deburring requirements and minimum cost machining-deburring conditions. In o r d~r to establish the generality of th" Burr Formation Mecha- nisms the four principle machining operations (drilling , milling, turning. and grindmg) were studied. The Burr Formation Mechanisms and resulting properti<>s are described ana l ytically a nd empiricillly. The author is indebted to the Bendix Corporation for providing the timP to pursue this study and for th e graduate fellowship which made it possible to return to graduate study. The many excellent suggestions from Dr. P. T. Blotter, Dr . Carl D. Spear. and Professor W. Karl Somers provided many of the links required to tie the theory and empirical rPsults together. Robert Poor's assistance in making the 1000 burr mPasurements is also gratefully acknowledged. Finally. I owe a special d0bt of gratitude to my wife who stood pati<>ntly hy while her husband engrossed himself in this study. LaRoux 1<. Gillespie iii TARLE OF CONTENTS Page ACKNOWLEDGMENTS LIST OF T.A BLES . iv LIST 0 F" PIG UR ES. vii DEFINITION OF TERMS AND SYMBOLS. xi ABSTRACT ... xiii INTRODUCTION. Statement of Problem Objective of the Study 2 Method of Approach . 2 BASIC MECf!ANISMSOF BURR FORMATION . 4 BURR FORMATION AND PROPERTIES IN SPECIFIC 0 PERA TIO NS . .. 23 Turning Operations 23 Milling Operations 36 Grinding Operations. 61 Drilling Operations 65 GENERAL COMMENTS 71 CONCLUSIONS AND RECOMMENDATIONS 73 BIBLIOGRAPHY. 76 APPENDIXES 80 Appendix A. Derivation of Burr Equations 81 Appendix B. Burr Measurement Data . 126 App<enrlix C. Analysis of Variance Results 142 iv LIST OF TA 8LES Table Page I. Variables studic'd in t urning t0sts 29 2. Side milling lpst conditions. 47 3 ANOVA results for side milling. 48 4. Typical lengths of side milling burrs 49 5. Relative burr thi ckness of side milling buns 50 6. End milling conditions studied 55 7. ANOVA results for end milling 57 8. Typical properti~s of end milling burrs 57 9 . D r illing test conditions . 68 Al. Strain hardening data 90 A2. S train in bending 95 A3. Ridge dl,, ct and Meye r n' value II 7 ;-1 , Results of turning tests 1 29 B2. End mi l1 ing test conditions 132 B3 . Measured burr length . 134 B4. Measur<'d burr thickness 136 B5. Measun·d burr l0ngths. Sid<> milling t<·sts 1 38 B6. MPasur<'d burr l<'ngths. ";rinding burrs 139 B7 Measu rpcl burr lengths and thickness 1 40 v LIST OF TABLES (Continued) Tabl,. Page Cl. Analysis of variance . Turning-burr lengths ~42 cz. Analysis of varianc e . End mill - Burr No. length 143 C3. Anal ysis of variance. End mill - l=)urr No. ' length 144 C.f. Analysis of variance . End mill - Hurr No . 5 length 144 cs. Analysis of variance. End mill- Burr No . 6 length 145 C6 . Analysis of vari anc P. End milling - Bu rr No. 8 length 145 C7. Analysis of variance. End milling Burr No . 9 length 146 C8. Analysis of variance>. Side 1nilling - Burr No. length 1 '6 C9. Analysis of variancp. Side milling - Burr No . 2 length 147 ClO. Analysis of variance . Side milling - bu rr No. 3 length 147 Cll. Analysis of variance . Side milling - Burr No. .. length 148 c 1 2. Analysis of variance. Side milling - Burr No. length 148 c 13. Analys i• ui variance. Side milling - Burr No. 6 length 146 c 14. Analysis of variance. Side milling - Burr No . 7 length 149 c 15. Analysis of variance . Side milling - Bur r No. 8 length ! 5 0 vi LIST OF' 1 A RLES (Continued) Table Pag" C 16. Analysis of variancP. Drilling - Top burr length. 150 C 17. Analysis of variance. Drilling- Bottom burr l ength 151 vii LIST OF Fit.iURES Figure Page 1. Schematic illustration of the cutting edge . 6 2. Pressures on flank surface . 7 3. Bulging caused by indentation of cylinder 8 4. Effecl of strain hardening exponent on ridging 13 5. Illustration of a Roll-Over Burr produced by pnd mill 14 6. Roll-Over Burr 1 6 7. Simplified illustration of burr formation in orthoginal milling . 19 8. Separalion o f initial chip in sidP n1illing 20 9. Chip forlTlation in n1achining 22 10. Burrs forn1cd in the basic turning operations 24 11. Burrs producC'd in turning 25 1 2. Burrs producpci in facing. 26 13. Burrs proclucC>d by plunge cutting 28 1-1. Effect of fC>edratp and SCEA on burr length. 31 1'i. Effect of ckpth of cut and SCEA on hurr length 31 1 6. Effect of iecdralE' and SCEA on burr thickness . 32 11. Side cutting edge angle 35 18. J:.:ffe c t of SCEA and true r ake on burr thickness 35 19. Effect of d<•pth of cut and SCEA on burr length 37 20. Effect of depth of cut and SCEA on burr thickness 37 viii L IST OF FIGURES (Continued) Figure Page 21 . Burrs produced in side milling . 38 22a. Milling cutte r path and chip sizP 40 22b. Tooth C>xitin g from workpiece 40 23. Chip seperation and tear type burr in millin g 4 1 24a. Cutter exiting from workpiece 43 24b. Tooth position at cutter exit . 43 25. Path gener ated by a plain milling cutter in climb m illing 44 26. Illustration of climb cut Pnlranc.c hurr 4 5 27. Edge angles r esulting from a helix angle 46 28 . Effects of machining conditions on side milling burrs 5 1 29. Identification of burr locations in C>nd milling 5 3 30. Identification of burr locations in end milling 54 31. Effect o( radial depth of cut on Roll-Over Burr 56 3 2. Effects of machining conditions on end milling bur rs 58 33. Effects of machining conditions on end milling burrs 59 34. Effects of machining conditions on end milling burrs 60 3 5. Effective rake angl" and burr location in grinding 63 36. Effects of machin ing conditions on grinding burrs 6-t 37. Roll-Over Burr formed in drilling 66 ix LIST OF .FIGURES (Continued) Figure Page 38. Typical burr formation in drilling. 67 39. Effect of drilling variables on burr s ize 69 A l . Chip deformation modes 83 A2. Cutting action near e dge 84 A3. Beam in bending 85 A4. Perfectly plastic behavior 87 A5. Burrs and bulgin g in chip formation 98 A6. C utting tool action 99 A 7. Assumed stress distribution a t effective cutting radius 99 AS. Geometry of equivalent pressurized cylinde r . I 0 1 A9 . State of s tress on a n infinitesimal clement. 102 AlO. Ellipse of plasticity . 106 All. Deformation of workpiece 10 6 A l 2. Plastic expans ion of a hole. 111 A l 3 . Sources of flan k pressure . 11 4 Al4. Displacements producc•d by lubricated wedge in perfectly plastic material . 11 b A l 5. Material dis placement using spherical indenters 11 8 Al6. Idealized model of chip 1 22 AI 7. Free body diagram at point B 122 X LIST OF FIGURES (Continued) Figure P age A l B. P l astic work in shear . .. 1 23 A l 9. Tear Burr modes of failure I 25 xi DEFINITION OF TERMS AND SYMBOLS b width of cut BHN Brinell Hardness Number BUE built up edge c machining constant, different for eac h material d radial depth of c ut in milling df degrees of freedom E modulus of e lasticity feedrate in inches per revolution F - main c utting force c F feed force (in direction of tool motion) a thrust force (in radial direction) tnaterial hardness bending moment Meyer Hardness Number n strain hardening exponent n' Meyer Strain Hardenability Exponent SCEA Side Cutting Edge Angle depth of c ut in turning instantaneous depth of cut v cutting velocity (in surface feet per minute) xii Q clearance angle rak" angle true strain true strain at fracture (in tensile test) HPlix Angle point angle on a drill u coefficient of friction v Poisson's Ratio (0. 5 for plastic materials) p radius of c urvature (T stress at the elastic limit e (T strain hardening constant 0 (T plastic stress p (T shear strPSS s T friction angle plasticity angle relating tang e ntial to radial stress plasticity angle at radius a shear angle xiii ABSTRACT The Formation and Properties of Machining Burrs by LaRoux K. Gillespie, Master of Sd,.nce Utah Stale University, 1973 Majo r P r ofessor: Dr .
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