Although almost any book and/or text on metal cutting, cutting tool design, and
$ F% X5 k0 o6 e% w5 D4 \' \+ umanufacturing process discusses to a certain extent the tool geometry, the body of 9 w- u9 T$ g9 f5 [
knowledge on the subject is scattered and confusing. Moreover, there is no clear $ ` L. `) S0 b) M7 M
objective(s) set in the selection of the tool geometry parameters so that an answer # s5 |! p0 m) W) ^! {* w; U; Z
to a simple question about optimal tool geometry cannot be found in the literature
5 ^* T4 l! e* U# W( {+ u( E2 |on the subject. This is because a criterion (criteria) of optimization is not clear, on
% }% u! F9 d7 ~7 k0 `one hand, and because the role of cutting tool geometry in machining process 1 l! c7 p* N4 V# E
optimization has never been studied systematically, on the other. As a result, many w& t) E6 r e6 u
practical tool/process designers are forced to use extremely vague ranges of tool 9 m o; h. t2 ^* Z6 T; O% c% y
geometry parameters provided by handbooks. Being at least 20+ years outdated, 0 v( r0 a: r( ]8 Z! o% _9 o
these data do not account for any particularities of a machining operation including 5 w0 ^& {) T, b, P0 a+ w
a particular grade of tool material, the condition of the machine used, the cutting 9 s4 ]6 @' d+ o7 n/ V
fluid, properties and metallurgical condition of the work material, requirements to
/ s, d+ V; t$ l, V2 s1 Gthe integrity of the machined surface, etc.
, y+ P2 z& ^' ^7 bUnfortunately, while today's professionals, practitioners, and students are 9 J8 O; N4 h( r1 i0 G' m
interested in cutting tool geometry, they are doomed to struggle with the confusing
9 Z, l3 u& O I7 vterminology. When one does not know what the words (terms) mean, it is easy to ! x7 ?0 ^: ~, h8 W2 S8 q5 t
slip into thinking that the matter is difficult, when actually the ideas are simple, 4 c! W7 U d# p, `* t3 V
easy to grasp, and fun to consider. It is the terms that get in the way, that stand as a
. A5 b7 D* Y D* s/ i7 Nwall between many practitioners and science. This books attempts to turn those . s7 d, u$ Q, u' ?
walls into windows, so that readers can peer in and join in the fun of proper tool 1 r6 \' q) u: f# _' i& K( _% P
design. # I; s7 A L- ^8 m4 m% K
So, why am I writing this book? There are a few reasons, but first and foremost, - J# {! R7 q l M- S- v
because I am a true believer in what we call technical literacy. I believe that
) V7 W" v, u9 Y2 }everyone involved in the metal cutting business should understand the essence and
$ r& C( @4 `$ V. v4 @ b4 dimportance of cutting tool geometry. In my opinion, this understanding is key to
, k' G$ v: ` eimproving efficiency of practically all machining operations. For the first time, this
' z, A1 K$ `! |6 _6 M) cbook presents and explains the direct correlations between tool geometry and tool ( N1 N2 A7 t) x" R$ W2 R% b7 i" Q
performance. The second reason is that I felt that there is no comprehensive book
0 S$ ~* B6 Z( ?5 k$ `- Eon the subject so professionals, practitioners, and students do not have a text from
; H* W7 c& @! Swhich to learn more on the subject and thus appreciate the real value of tool
) @2 j3 f, e6 p0 P! i9 Sgeometry. Finally, I wanted to share the key elements of tool geometry that I felt + y, s" K: J% o; v
were not broadly understood and thus used in the tool design practice and in
6 Z! O, t+ O: K$ S) ~7 P( @optimization of machining operations in industry. Moreover, being directly . i6 Z% c" R$ b; E8 l; g- o0 N
involved in the launch of many modern manufacturing facilities equipped with $ S" E; a P q
state-of-the-art high-precision machines, I found that the cutting tool industry is not ; f( J" l2 ^+ x5 R, h6 ]
ready to meet the challenge of modern metal cutting applications. One of the key , p- V1 ^& U( O, V6 p+ j1 A
issues is the definite lack of understanding of the basics of tool geometry of , S6 J; ?4 K% T+ y! [
standard and application-specific tools.
. h: X- T! ^1 NThe lack of information on cutting tool geometry and its influence on the
$ S3 J( }: D8 ^7 {) m: J x3 T2 Uoutcome of machining operations can be explained as follows. Many great findings
0 t1 ~3 a* B/ o/ ~2 ~. P* G3 gon tool geometry were published a long time ago when neither CNC grinding
; V' F- t) G) O1 a6 Q0 T" smachines capable of reproducing any kind of tool geometry were available nor
% o, w6 r+ y) c: Z$ G1 d2 y) Nwere computers to calculate parameters of such geometry (using numerical
! B# `9 t/ C0 U% u# ^7 w( V0 omethods) common. Manual grinding using standard 2- and 3-axis simple grinding
# r0 J4 R. I/ Z8 e9 d* Efeatures was common so the major requirement for tool geometry was the simpler 9 p4 b4 n- N+ u S' U# T
the better. Moreover, old, insufficiently rigid machines, aged tool holders and part
6 c$ m( F. f% u+ ffixtures, and poor metal working fluid (MWF) selection and maintenance levered ( a1 C. D) ^0 t, }5 Y
any advancement in tool geometry as its influence could not be distinguished under ! J7 |# i6 c5 i$ c/ W
these conditions. Besides, a great scatter in the properties of tool materials in the
3 ]; Q& h, f) d- H) j% B+ Wpast did not allow distinguishing of the true influence of tool geometry. As a result, 8 R5 I- [/ k. y. S# W6 N
studies on tool geometry were reduced to theoretical considerations of features of . V; E4 `. q9 ^5 U& i# X
twist drills and some gear manufacturing tools such as hobs, shaving cutters,
1 A, ^ y! Z0 @( {! R j3 ushapers, etc.
- F( r& U' J9 wGradually, once mighty chapters on tool geometry in metal cutting and tool ) Q% u9 }/ u4 |" f
design books were reduced to sections of few pages where no correlation between ) [2 w" K4 t) _5 {( x9 c4 S
tool geometry and tool performance is normally considered. What is left is a ( N6 d9 ]$ q7 H% z* e( D0 |
general perception that the so-called “positive geometry” is somehow better than
$ r, ]' C6 R; O& b- Z9 Z) ]3 n“negative geometry.” As such, there is no quantitative translation of the word # e+ b ^/ o( X, U
“better” into the language of technical data although a great number of articles / o& N; s. r" m7 K5 ^$ _
written in many professional magazines discuss the qualitative advantages of
7 y" d; l: [* M9 X4 v# F“positive geometry.” For example, one popular manufacturing magazine article
( [9 D. Q# T) t& _% Iread “Negative rake tools have a much stronger leading edge and tend to push
9 Y7 _; V+ l' d( _4 Fagainst the workpiece in the direction of the cutter feed. This geometry is less free ) p8 Q8 |' r5 a! b8 f
cutting than positive rakes and so consumes more horsepower to cut.” Reading ; B. X9 x- V6 U/ {) v) z# p. F k
these articles one may wonder why cutting tool manufacturers did not switch their
# r4 J3 K. p! X. _tool designs completely to this mysterious “positive geometry” or why some of 9 _+ t( A2 g# \4 x; M* Y
them still investigate and promote negative geometry.
7 J5 J' j! r6 }3 U5 t3 _% nDuring recent decades, the metalworking industry underwent several important
/ U- S: t& P; [changes that should bring cutting tool geometry into the forefront of tool design
& j% Y l8 D) x' ]: mand implementation: |