Although almost any book and/or text on metal cutting, cutting tool design, and 4 L# J- Z) D' x, V
manufacturing process discusses to a certain extent the tool geometry, the body of 8 e- W; R7 g$ N* _. ~
knowledge on the subject is scattered and confusing. Moreover, there is no clear 2 Y n& Z- B# s5 ^' s* l
objective(s) set in the selection of the tool geometry parameters so that an answer
0 J6 @- Q4 ^" g3 h/ O3 U4 w' Oto a simple question about optimal tool geometry cannot be found in the literature
1 Y4 W0 N+ c4 ]: Aon the subject. This is because a criterion (criteria) of optimization is not clear, on ! i. @: |) Y( r: H& _2 O- U
one hand, and because the role of cutting tool geometry in machining process
! j* S; z; {: R2 e6 N1 C. ~optimization has never been studied systematically, on the other. As a result, many
& Q' B6 _/ g; j' Gpractical tool/process designers are forced to use extremely vague ranges of tool
, P3 w/ E5 W' a/ Q) G/ Q; Fgeometry parameters provided by handbooks. Being at least 20+ years outdated,
5 ^$ i- }3 \4 I; uthese data do not account for any particularities of a machining operation including
; A) O0 ^8 R) ^4 o! v" _ q1 Fa particular grade of tool material, the condition of the machine used, the cutting 5 H* K, T) [/ w. _' Z
fluid, properties and metallurgical condition of the work material, requirements to
9 i) ~, A6 L6 Z5 m+ rthe integrity of the machined surface, etc.
8 i; g. B, `) @* E0 JUnfortunately, while today's professionals, practitioners, and students are
3 |( n5 \5 W- C- Y9 i' Jinterested in cutting tool geometry, they are doomed to struggle with the confusing & {, f! D" A8 T2 |
terminology. When one does not know what the words (terms) mean, it is easy to
$ G, [0 g" Y1 U, f$ D! d: islip into thinking that the matter is difficult, when actually the ideas are simple, 0 i; {( I7 q% e; M1 f6 n
easy to grasp, and fun to consider. It is the terms that get in the way, that stand as a
4 P* n \2 L9 w3 x/ Lwall between many practitioners and science. This books attempts to turn those
6 I# V" O. n: E1 Bwalls into windows, so that readers can peer in and join in the fun of proper tool
* L! X% I! C: v$ V4 [design.
3 w" r# B% [) K4 o! ^, L( VSo, why am I writing this book? There are a few reasons, but first and foremost,
! T) Q. p- {; z8 L! k4 xbecause I am a true believer in what we call technical literacy. I believe that
1 c% r/ B, D7 a) J) ~ [3 y7 Feveryone involved in the metal cutting business should understand the essence and % \* c3 w0 c4 R5 Z1 V
importance of cutting tool geometry. In my opinion, this understanding is key to
2 r! y8 B& ^1 r% I) H5 t) timproving efficiency of practically all machining operations. For the first time, this $ w) i* E+ J4 {- g
book presents and explains the direct correlations between tool geometry and tool
# \2 U _1 G$ Y Rperformance. The second reason is that I felt that there is no comprehensive book * h4 g! k5 u" z$ N0 t7 u
on the subject so professionals, practitioners, and students do not have a text from * b) C# e& M/ _# |
which to learn more on the subject and thus appreciate the real value of tool ! _+ K3 D$ M0 {: P) y: U/ k
geometry. Finally, I wanted to share the key elements of tool geometry that I felt ; S y/ H9 |# F# o7 A5 y/ e6 |$ o# u, i
were not broadly understood and thus used in the tool design practice and in
' t2 x H+ x, H$ L: L# Ooptimization of machining operations in industry. Moreover, being directly
$ a! m1 h% d4 T" g1 a' S* Ainvolved in the launch of many modern manufacturing facilities equipped with " i) M) ]9 H# g1 e
state-of-the-art high-precision machines, I found that the cutting tool industry is not
3 K7 v7 F& I2 s rready to meet the challenge of modern metal cutting applications. One of the key
6 w7 e9 M7 s) i9 h6 V/ Iissues is the definite lack of understanding of the basics of tool geometry of 0 f( T( b( t% H
standard and application-specific tools.
7 K$ Q$ l/ {5 y ^& z$ i1 [The lack of information on cutting tool geometry and its influence on the
3 S% p# L; k( T; C2 I$ u9 xoutcome of machining operations can be explained as follows. Many great findings + O; R' i5 H' X; f+ d. r
on tool geometry were published a long time ago when neither CNC grinding 9 \& N4 `+ r9 }2 y
machines capable of reproducing any kind of tool geometry were available nor ) {' R5 F. c7 w% b7 q% o
were computers to calculate parameters of such geometry (using numerical
) y' r9 N7 J6 R# q, g: n8 ]3 {methods) common. Manual grinding using standard 2- and 3-axis simple grinding 3 ^9 }) i9 \+ n, q# g- v
features was common so the major requirement for tool geometry was the simpler , |5 \! \- X( Q, I* L5 |
the better. Moreover, old, insufficiently rigid machines, aged tool holders and part
% y0 R. P- i- \4 R- @fixtures, and poor metal working fluid (MWF) selection and maintenance levered ; E' V1 e& X3 B1 K6 ~: |3 Z
any advancement in tool geometry as its influence could not be distinguished under - r! {$ t9 b3 W0 U9 _4 `* g
these conditions. Besides, a great scatter in the properties of tool materials in the & W! D. {9 Z, o* P+ U/ ]
past did not allow distinguishing of the true influence of tool geometry. As a result, : l# o/ F% @$ |* d5 x' L) Q: l2 H
studies on tool geometry were reduced to theoretical considerations of features of 3 r3 W' a& a8 c5 Z8 a
twist drills and some gear manufacturing tools such as hobs, shaving cutters,
$ C9 s: N& E, ~4 v+ U; Yshapers, etc.
n! j' W- v1 I1 a6 QGradually, once mighty chapters on tool geometry in metal cutting and tool 0 ^. n, s; X, n$ z e
design books were reduced to sections of few pages where no correlation between ! Q& L0 b( P% D/ @+ ?
tool geometry and tool performance is normally considered. What is left is a " Q. ~! \# c7 J7 p7 R; u7 L
general perception that the so-called “positive geometry” is somehow better than
9 r2 V" n% f, w& L; T i0 i# f“negative geometry.” As such, there is no quantitative translation of the word ) m! y3 s* D6 x+ ~( f- y. f2 ~
“better” into the language of technical data although a great number of articles
/ _) y0 x2 ]9 |' n% B4 v" |written in many professional magazines discuss the qualitative advantages of
) G- N( g+ w. o+ a; D+ g. S8 H“positive geometry.” For example, one popular manufacturing magazine article ! E4 w o k$ M6 X0 O3 }) m. A
read “Negative rake tools have a much stronger leading edge and tend to push ; a. R# G& D7 g( z( r3 a! g
against the workpiece in the direction of the cutter feed. This geometry is less free 4 |# e: Q: Q$ Y6 Z
cutting than positive rakes and so consumes more horsepower to cut.” Reading
: }+ ?! ^% \* mthese articles one may wonder why cutting tool manufacturers did not switch their
% c! l( l" A9 l) Z" ?4 F! Otool designs completely to this mysterious “positive geometry” or why some of / @6 M* \, u, P O( X0 f
them still investigate and promote negative geometry. 1 O5 v) d1 t t! q: i t& C, T
During recent decades, the metalworking industry underwent several important
' j7 S2 C& Q) h! Echanges that should bring cutting tool geometry into the forefront of tool design $ O$ @: k$ [3 Y X
and implementation: |