Although almost any book and/or text on metal cutting, cutting tool design, and ' f3 @3 H% F5 r: y& D, E. t4 I# B9 K
manufacturing process discusses to a certain extent the tool geometry, the body of
5 w$ M8 r2 @+ k9 I* f9 z/ hknowledge on the subject is scattered and confusing. Moreover, there is no clear 0 S7 v$ O t U: F! R, |
objective(s) set in the selection of the tool geometry parameters so that an answer
% B8 K' U4 b! ~% r$ p# u! a& ^$ |to a simple question about optimal tool geometry cannot be found in the literature
' R" D3 z) M! H$ A. d; o% a; eon the subject. This is because a criterion (criteria) of optimization is not clear, on
9 S5 N; |- C4 W5 [, [one hand, and because the role of cutting tool geometry in machining process 8 F0 ^# t) [" N+ p4 @7 Y
optimization has never been studied systematically, on the other. As a result, many
* h1 Z U: \5 p- ~. P) \practical tool/process designers are forced to use extremely vague ranges of tool 1 ~9 B2 G0 e! h' h, i: n: P
geometry parameters provided by handbooks. Being at least 20+ years outdated,
0 H+ N& o% ]+ n5 _these data do not account for any particularities of a machining operation including
! _$ N( {, d, E, Ea particular grade of tool material, the condition of the machine used, the cutting & I- H8 R- W8 W' m
fluid, properties and metallurgical condition of the work material, requirements to
; N' ~' B- U8 _/ J/ D4 }4 Fthe integrity of the machined surface, etc. ( {% H2 z) x3 `+ C; o" a
Unfortunately, while today's professionals, practitioners, and students are * B7 W# m' q8 E* o4 M" w; T$ g
interested in cutting tool geometry, they are doomed to struggle with the confusing
, X/ B3 U- t4 s; a6 f% `- C5 Eterminology. When one does not know what the words (terms) mean, it is easy to
! o9 `# e, a: _2 F; X# y7 W* S( ^slip into thinking that the matter is difficult, when actually the ideas are simple,
( r: B1 x- {; m- Neasy to grasp, and fun to consider. It is the terms that get in the way, that stand as a
- p' ^' [# i0 @: c- d: D4 z @wall between many practitioners and science. This books attempts to turn those 8 H# w0 `" M' }- a" y4 \ X
walls into windows, so that readers can peer in and join in the fun of proper tool
) ^# S% |2 L" A C4 [design. ( L* `) j0 }9 H% A/ H4 A& x8 g# k0 o
So, why am I writing this book? There are a few reasons, but first and foremost, 2 I( W" M: {' m" C2 ?6 c, T' J
because I am a true believer in what we call technical literacy. I believe that
0 k1 t1 F- `' U* {( b2 l7 k1 A9 [everyone involved in the metal cutting business should understand the essence and
9 M J3 o! h* L* Z5 m0 h2 ?importance of cutting tool geometry. In my opinion, this understanding is key to
$ U4 \4 U$ W+ i$ M" T! i$ ~improving efficiency of practically all machining operations. For the first time, this
# G. m, ~- G! ^0 b( q( Hbook presents and explains the direct correlations between tool geometry and tool
! s, ]4 E v% X. Hperformance. The second reason is that I felt that there is no comprehensive book
8 ?# _! x# |% |1 Q7 Z2 j& zon the subject so professionals, practitioners, and students do not have a text from
: ^& o+ n( p! `7 R/ ^% Uwhich to learn more on the subject and thus appreciate the real value of tool * b( B- |$ X% I; s- l% l6 ]$ E
geometry. Finally, I wanted to share the key elements of tool geometry that I felt 1 I0 T4 M6 R* q* \: s0 |- P
were not broadly understood and thus used in the tool design practice and in
6 q" _* ^; s2 e4 j/ qoptimization of machining operations in industry. Moreover, being directly
+ I# ^2 b5 f1 y# i, Jinvolved in the launch of many modern manufacturing facilities equipped with & ]9 ^; }2 x2 m1 _. _0 T" u
state-of-the-art high-precision machines, I found that the cutting tool industry is not
' T# a5 w+ ^3 x4 z7 Q$ Vready to meet the challenge of modern metal cutting applications. One of the key ( z8 \# Q& u! Q6 |6 v
issues is the definite lack of understanding of the basics of tool geometry of $ ]' F- w* H& U6 b. Q6 P
standard and application-specific tools. ) u* q5 G' A; m
The lack of information on cutting tool geometry and its influence on the
6 W1 J; k. ^! O9 w# }& C6 _outcome of machining operations can be explained as follows. Many great findings , K$ `. W% ~0 |) F0 |8 ], l
on tool geometry were published a long time ago when neither CNC grinding
d4 `0 R/ D; ^' P4 e5 n+ umachines capable of reproducing any kind of tool geometry were available nor
4 Q0 J G( J. \% qwere computers to calculate parameters of such geometry (using numerical $ X/ z. B8 k" k. Y0 i
methods) common. Manual grinding using standard 2- and 3-axis simple grinding : l( \- t7 M. C$ f
features was common so the major requirement for tool geometry was the simpler 4 w, U" R1 d& j9 K; P% k! P8 x
the better. Moreover, old, insufficiently rigid machines, aged tool holders and part $ g4 O% q) m8 s0 D/ ~& s' G
fixtures, and poor metal working fluid (MWF) selection and maintenance levered
" p" U) G0 a8 r! T! B aany advancement in tool geometry as its influence could not be distinguished under
; \1 s9 `( J7 Othese conditions. Besides, a great scatter in the properties of tool materials in the
9 S4 r x5 P2 c) m6 Gpast did not allow distinguishing of the true influence of tool geometry. As a result,
2 L( F9 w4 K q) f( S( Ystudies on tool geometry were reduced to theoretical considerations of features of # n Q. _) x$ X: r
twist drills and some gear manufacturing tools such as hobs, shaving cutters, " z, w# z; I5 [
shapers, etc. 5 b9 U0 d. Z2 v
Gradually, once mighty chapters on tool geometry in metal cutting and tool 5 m4 [# ~- o7 P' {
design books were reduced to sections of few pages where no correlation between ) J3 {3 t( @1 _5 t5 \: z
tool geometry and tool performance is normally considered. What is left is a
4 n0 S0 M I% a+ H3 c( D; Q- _6 F, Pgeneral perception that the so-called “positive geometry” is somehow better than
6 h! K3 U3 n+ ^( ~7 y“negative geometry.” As such, there is no quantitative translation of the word 0 F5 M. O; z3 O( U) }. L& |
“better” into the language of technical data although a great number of articles
! I) E, `, Y+ l% pwritten in many professional magazines discuss the qualitative advantages of
8 |0 Y' f3 D- _: {- D# z5 N( L“positive geometry.” For example, one popular manufacturing magazine article
m6 T1 d; d3 Kread “Negative rake tools have a much stronger leading edge and tend to push
% y& x4 n/ L, s2 Yagainst the workpiece in the direction of the cutter feed. This geometry is less free - \* L* W/ e! t( o( M7 L
cutting than positive rakes and so consumes more horsepower to cut.” Reading 5 U' A6 Y" R5 w1 h2 @
these articles one may wonder why cutting tool manufacturers did not switch their / C d8 E1 l; f
tool designs completely to this mysterious “positive geometry” or why some of
: k1 Q _! }' K- jthem still investigate and promote negative geometry.
9 E/ a& O4 N1 G6 p/ P" X3 cDuring recent decades, the metalworking industry underwent several important * X' L/ t7 R5 q/ I
changes that should bring cutting tool geometry into the forefront of tool design
+ z/ y$ _/ u! O; M* o# band implementation: |