Although almost any book and/or text on metal cutting, cutting tool design, and 8 r- I4 d& \5 X8 {
manufacturing process discusses to a certain extent the tool geometry, the body of ' k2 \# ]& [% K
knowledge on the subject is scattered and confusing. Moreover, there is no clear * ]& R7 y5 ~" }1 B& ]7 l
objective(s) set in the selection of the tool geometry parameters so that an answer ' J9 i& Y% c6 I3 p; K/ z1 ?& p' S
to a simple question about optimal tool geometry cannot be found in the literature ( x3 q; m/ C1 Q$ g( F7 F' K- V5 Y
on the subject. This is because a criterion (criteria) of optimization is not clear, on ) u6 @# M) o* `" ]
one hand, and because the role of cutting tool geometry in machining process # k/ P; r1 P1 v5 _( r, b( }
optimization has never been studied systematically, on the other. As a result, many
% I* h9 J& H) O( ~5 b& Gpractical tool/process designers are forced to use extremely vague ranges of tool
9 |5 T6 y; q5 T" ygeometry parameters provided by handbooks. Being at least 20+ years outdated, ' Q! E; h0 U4 n5 z
these data do not account for any particularities of a machining operation including
8 Y* x- {& r, Sa particular grade of tool material, the condition of the machine used, the cutting / k) f5 N5 V- G2 W7 w6 `4 o1 u1 ^
fluid, properties and metallurgical condition of the work material, requirements to 5 L6 A0 Y% y, t5 u( a1 v% V
the integrity of the machined surface, etc.
7 u9 r& F w3 w! X/ k$ {, SUnfortunately, while today's professionals, practitioners, and students are
. d ^* ]/ J7 l! Q) yinterested in cutting tool geometry, they are doomed to struggle with the confusing 4 p. C: y8 F6 a! Q: P
terminology. When one does not know what the words (terms) mean, it is easy to
, q- W! b, F: O6 \5 D8 b! `/ Z) c4 tslip into thinking that the matter is difficult, when actually the ideas are simple,
+ T* h* d- p4 Ceasy to grasp, and fun to consider. It is the terms that get in the way, that stand as a ) ]4 i( }4 k- q
wall between many practitioners and science. This books attempts to turn those
2 K$ H: P) J G+ Pwalls into windows, so that readers can peer in and join in the fun of proper tool
W8 o' r/ R& d# T; Ydesign. ) T7 b/ L' b1 ^
So, why am I writing this book? There are a few reasons, but first and foremost,
* E% F) A- B4 ]# j. @% v8 ^ xbecause I am a true believer in what we call technical literacy. I believe that ) P0 }2 T! [, Z, b9 n# v: Y' `0 h
everyone involved in the metal cutting business should understand the essence and
( F2 Z Y- j4 q T( Pimportance of cutting tool geometry. In my opinion, this understanding is key to ! V8 I' s9 u& x" [) U9 O. _( \
improving efficiency of practically all machining operations. For the first time, this
1 s6 R3 p. v0 r- y( o9 l3 r% _book presents and explains the direct correlations between tool geometry and tool
2 M, W6 J, w7 w: S% h1 w- ]performance. The second reason is that I felt that there is no comprehensive book % D5 p5 ?% g4 `
on the subject so professionals, practitioners, and students do not have a text from . [5 p+ ?& y S: M6 L
which to learn more on the subject and thus appreciate the real value of tool + P: C1 S/ R* x, z
geometry. Finally, I wanted to share the key elements of tool geometry that I felt " v5 ]6 T+ B+ p8 w! ~
were not broadly understood and thus used in the tool design practice and in
, x7 v3 f( g! w% n; o. a3 f; Woptimization of machining operations in industry. Moreover, being directly % Z; v8 U+ Q* A& @; x9 N0 V
involved in the launch of many modern manufacturing facilities equipped with
0 {& V3 K! H1 P+ j4 y3 ~state-of-the-art high-precision machines, I found that the cutting tool industry is not
0 [$ L/ p4 G+ {) @; Y: Fready to meet the challenge of modern metal cutting applications. One of the key , `+ o6 P7 E" z1 f& T! m! i
issues is the definite lack of understanding of the basics of tool geometry of
4 X. m$ k0 N$ V3 z4 _0 }8 ?standard and application-specific tools.
8 ]% V8 i5 ^$ H7 T @* yThe lack of information on cutting tool geometry and its influence on the
$ P% s: ?% F% Coutcome of machining operations can be explained as follows. Many great findings
" T% }, A+ Z+ |+ r0 F+ `& n) y- don tool geometry were published a long time ago when neither CNC grinding
. T s* s1 D7 @& P) Amachines capable of reproducing any kind of tool geometry were available nor
x _. a9 c& zwere computers to calculate parameters of such geometry (using numerical
9 e" I7 B1 Z; |% m5 |1 h" lmethods) common. Manual grinding using standard 2- and 3-axis simple grinding
& j1 N" t3 R6 _features was common so the major requirement for tool geometry was the simpler
/ Z5 e+ F) J9 `/ Uthe better. Moreover, old, insufficiently rigid machines, aged tool holders and part
w3 a3 Y, a) @" Nfixtures, and poor metal working fluid (MWF) selection and maintenance levered
- w% B* n! `& Y9 R# J/ e; I5 _any advancement in tool geometry as its influence could not be distinguished under 6 j0 L1 h9 D' m& ~
these conditions. Besides, a great scatter in the properties of tool materials in the & \, x; c6 S* N1 {( t
past did not allow distinguishing of the true influence of tool geometry. As a result, ; ?( `; Y; J+ ?2 V0 e" U, _) i' E
studies on tool geometry were reduced to theoretical considerations of features of i. ^; z6 a& V3 J" i
twist drills and some gear manufacturing tools such as hobs, shaving cutters, ! m* j# e0 j* Q% {& f: C3 Y
shapers, etc.
9 ]$ s _1 @9 l1 W; rGradually, once mighty chapters on tool geometry in metal cutting and tool
# y# x9 m* l/ R; C% {- Udesign books were reduced to sections of few pages where no correlation between 9 V2 p' ^, D2 V/ U6 v
tool geometry and tool performance is normally considered. What is left is a - w! K: j) X& k. l+ l8 o
general perception that the so-called “positive geometry” is somehow better than
/ ]1 V$ H ?, `/ w8 W( b“negative geometry.” As such, there is no quantitative translation of the word " R% W0 R) Q+ u1 O9 I( S
“better” into the language of technical data although a great number of articles 3 w) P5 U! U! m/ F: r4 ^8 y
written in many professional magazines discuss the qualitative advantages of
( v* N( q3 c9 M, q$ N“positive geometry.” For example, one popular manufacturing magazine article
( M' _; j6 D3 `2 M& n3 cread “Negative rake tools have a much stronger leading edge and tend to push
" H3 q) p9 U, Q& h M% }3 Dagainst the workpiece in the direction of the cutter feed. This geometry is less free ! r" D7 u. T% }% [) ?1 ?
cutting than positive rakes and so consumes more horsepower to cut.” Reading
' j: k. `3 d3 @; Z9 Y z4 Mthese articles one may wonder why cutting tool manufacturers did not switch their 3 J* Q6 T% c0 g' ~. _- f" J
tool designs completely to this mysterious “positive geometry” or why some of
+ ~6 [8 u9 T+ v- N, Tthem still investigate and promote negative geometry.
1 O* `( L; m+ J2 t8 b/ y+ MDuring recent decades, the metalworking industry underwent several important & J' L# ]8 w1 k, \2 {! c
changes that should bring cutting tool geometry into the forefront of tool design
. Q0 m# Z; i$ m5 d+ L, ~% M7 ]and implementation: |