Although almost any book and/or text on metal cutting, cutting tool design, and , y+ k$ g0 o# m8 a3 P
manufacturing process discusses to a certain extent the tool geometry, the body of 6 {' v3 y! D2 `) n
knowledge on the subject is scattered and confusing. Moreover, there is no clear A9 z& J1 y, y) \6 w
objective(s) set in the selection of the tool geometry parameters so that an answer ( I, X, l& d2 J4 F& l# |) R" `/ Z
to a simple question about optimal tool geometry cannot be found in the literature ) b7 a& E' _" m, M ?
on the subject. This is because a criterion (criteria) of optimization is not clear, on + L" k4 b" g$ R6 c9 X
one hand, and because the role of cutting tool geometry in machining process ( B6 _# B& \2 T/ `* I. L, O
optimization has never been studied systematically, on the other. As a result, many / j/ }4 v, m V' z) V' M5 r) t- R
practical tool/process designers are forced to use extremely vague ranges of tool . [9 i# ^- g7 k8 I
geometry parameters provided by handbooks. Being at least 20+ years outdated,
& l: g7 {( o' v5 H5 z( h; t3 zthese data do not account for any particularities of a machining operation including 4 K5 ?3 Y/ r& E
a particular grade of tool material, the condition of the machine used, the cutting
9 e8 K- @( N$ y" @fluid, properties and metallurgical condition of the work material, requirements to ) T% x6 x1 o) O7 ~. G4 K6 R
the integrity of the machined surface, etc.
) A' I) v( B1 s0 f$ m5 YUnfortunately, while today's professionals, practitioners, and students are - l! G9 `( g6 r6 ]9 d, v
interested in cutting tool geometry, they are doomed to struggle with the confusing
6 S* @7 u4 S0 b+ R* hterminology. When one does not know what the words (terms) mean, it is easy to 3 s+ R/ [ l7 o K
slip into thinking that the matter is difficult, when actually the ideas are simple,
# V5 m2 D, h veasy to grasp, and fun to consider. It is the terms that get in the way, that stand as a ( j9 n: t! A$ f, S! J2 i; P3 z: [
wall between many practitioners and science. This books attempts to turn those ( j3 ]. [* Z- j+ x4 m9 ?5 g$ u1 B
walls into windows, so that readers can peer in and join in the fun of proper tool C1 q( Z" X6 v; G! ]) @
design. & Z, u3 L# R$ j3 m7 w: b- l
So, why am I writing this book? There are a few reasons, but first and foremost,
* r% j8 l* J" _7 dbecause I am a true believer in what we call technical literacy. I believe that
9 T5 h- U* d8 }" A Beveryone involved in the metal cutting business should understand the essence and - T5 j) m. L" u0 o$ n# T; S" i
importance of cutting tool geometry. In my opinion, this understanding is key to
7 c+ ^: c; k7 T( V- cimproving efficiency of practically all machining operations. For the first time, this 3 w+ H- s4 ~2 q5 E- J! s
book presents and explains the direct correlations between tool geometry and tool 7 [- r% g2 c5 [4 c f3 O, [
performance. The second reason is that I felt that there is no comprehensive book
* p T# H' Z/ |2 R' C) F! _on the subject so professionals, practitioners, and students do not have a text from ' E$ r, e3 B# \- h
which to learn more on the subject and thus appreciate the real value of tool 0 F7 f& _/ J9 ]6 f) _( l
geometry. Finally, I wanted to share the key elements of tool geometry that I felt 5 G e& p* k$ ]2 k: u3 O6 l
were not broadly understood and thus used in the tool design practice and in & | w! V0 u6 X& O% }6 l7 y
optimization of machining operations in industry. Moreover, being directly
+ ~0 i0 s0 X# ^! k% Minvolved in the launch of many modern manufacturing facilities equipped with
! Q- a F {9 G6 o* tstate-of-the-art high-precision machines, I found that the cutting tool industry is not * B2 y! \) n K4 _9 b; a, L) p
ready to meet the challenge of modern metal cutting applications. One of the key % @6 F5 S l* P+ S
issues is the definite lack of understanding of the basics of tool geometry of
; i5 g( A9 e" O7 S# u2 jstandard and application-specific tools. ' @& Y0 o/ B" a( P X
The lack of information on cutting tool geometry and its influence on the . i0 M, K4 ^, p+ J8 d/ B* {5 ]* \
outcome of machining operations can be explained as follows. Many great findings
/ L' S2 }) f M$ ion tool geometry were published a long time ago when neither CNC grinding 4 g" B% `$ X5 s: T9 C
machines capable of reproducing any kind of tool geometry were available nor : v: R: \; G7 W' u0 T
were computers to calculate parameters of such geometry (using numerical 2 q! J6 z& Q t4 e( y5 {* O$ E' u' D
methods) common. Manual grinding using standard 2- and 3-axis simple grinding
. b; J4 g; h: R$ V& ]6 }features was common so the major requirement for tool geometry was the simpler
; z4 w/ ^( A3 j$ D9 fthe better. Moreover, old, insufficiently rigid machines, aged tool holders and part - x" X3 G, z/ M4 j7 m5 ?/ E
fixtures, and poor metal working fluid (MWF) selection and maintenance levered
% K+ ^, H' G! Hany advancement in tool geometry as its influence could not be distinguished under . I& j% n, N( b) W
these conditions. Besides, a great scatter in the properties of tool materials in the
2 K: Z; ^: a7 k* S0 j+ Qpast did not allow distinguishing of the true influence of tool geometry. As a result, + D, ^; _. ?+ M) p, w
studies on tool geometry were reduced to theoretical considerations of features of
/ Q& U1 c5 `& [+ a, Btwist drills and some gear manufacturing tools such as hobs, shaving cutters, , k; I2 ^% P0 `) z7 Q
shapers, etc.
$ D/ w+ t/ Q; l3 }3 ^Gradually, once mighty chapters on tool geometry in metal cutting and tool 2 V6 U& O& h N/ u% F9 \# q
design books were reduced to sections of few pages where no correlation between ' o) P* L- N0 q
tool geometry and tool performance is normally considered. What is left is a
8 O s; Q. ~. P1 L x( Egeneral perception that the so-called “positive geometry” is somehow better than
' z( n* |# h& H$ L+ i" Y“negative geometry.” As such, there is no quantitative translation of the word
|' N" X5 p0 i. X“better” into the language of technical data although a great number of articles
- h; r0 N/ M8 @9 a8 owritten in many professional magazines discuss the qualitative advantages of
9 ~; Z w9 t; U2 N“positive geometry.” For example, one popular manufacturing magazine article 8 B5 l( q0 `0 K1 w# G$ R8 L
read “Negative rake tools have a much stronger leading edge and tend to push
! G% w5 R) Y) w/ }against the workpiece in the direction of the cutter feed. This geometry is less free 5 A. e& t; |, S* a" K
cutting than positive rakes and so consumes more horsepower to cut.” Reading % J2 `& l; l1 I0 D! X8 P! D' E
these articles one may wonder why cutting tool manufacturers did not switch their
: n. ~1 w+ |4 C: w$ e+ ptool designs completely to this mysterious “positive geometry” or why some of / a2 d# i8 v8 K) r1 T7 f, H+ R
them still investigate and promote negative geometry. 5 S3 J' E+ _2 Q$ K
During recent decades, the metalworking industry underwent several important * [( f& U0 U6 b' G4 g1 a
changes that should bring cutting tool geometry into the forefront of tool design : `* [( q" t. |6 e4 j0 N' ^; N
and implementation: |