Although almost any book and/or text on metal cutting, cutting tool design, and
' u* }2 u" s/ Y& Z; Zmanufacturing process discusses to a certain extent the tool geometry, the body of 9 j0 r& |6 o+ s. Y9 r
knowledge on the subject is scattered and confusing. Moreover, there is no clear ( H1 _& ]/ n g* e/ O
objective(s) set in the selection of the tool geometry parameters so that an answer 9 ^: R/ c/ z; L, G# R( w5 X0 _* t
to a simple question about optimal tool geometry cannot be found in the literature ( A1 V( K5 n' p, G+ Q! k
on the subject. This is because a criterion (criteria) of optimization is not clear, on d t" ?- h6 y
one hand, and because the role of cutting tool geometry in machining process 7 g" K0 E+ n* e: V5 T
optimization has never been studied systematically, on the other. As a result, many ! D& \$ {, a- ~+ j7 i2 O2 W
practical tool/process designers are forced to use extremely vague ranges of tool
' h% L8 H4 {0 z3 i" z' ageometry parameters provided by handbooks. Being at least 20+ years outdated, ! `2 V4 ?/ I. v- A! ^1 s
these data do not account for any particularities of a machining operation including / O' x3 @7 r$ i- i
a particular grade of tool material, the condition of the machine used, the cutting , R) K+ M+ C* \0 v! ~+ S7 r
fluid, properties and metallurgical condition of the work material, requirements to
. c# v1 i3 c3 [the integrity of the machined surface, etc. 2 r& L9 q8 u! P* n9 V+ s
Unfortunately, while today's professionals, practitioners, and students are
8 L3 L, D$ J# T$ s& binterested in cutting tool geometry, they are doomed to struggle with the confusing 5 C! H2 D9 ]# w
terminology. When one does not know what the words (terms) mean, it is easy to , P9 N( w' c1 M; B* _. f( A6 q
slip into thinking that the matter is difficult, when actually the ideas are simple,
8 r/ |. |" ~8 g% T2 n/ ceasy to grasp, and fun to consider. It is the terms that get in the way, that stand as a ' m- J% X! {1 B' t q1 f$ S& Z4 l
wall between many practitioners and science. This books attempts to turn those
1 g/ O) D7 Q9 z/ l2 \8 {3 awalls into windows, so that readers can peer in and join in the fun of proper tool
) v% o' _" l: vdesign.
) L9 ~1 r# r/ G5 ~So, why am I writing this book? There are a few reasons, but first and foremost, 1 i, s0 r$ u0 F
because I am a true believer in what we call technical literacy. I believe that
1 h( v5 P1 b. r3 t% A# O8 yeveryone involved in the metal cutting business should understand the essence and , H P+ y$ P+ o* J4 C) e# V" x
importance of cutting tool geometry. In my opinion, this understanding is key to
* M- c" B' X7 x; ]4 G9 \improving efficiency of practically all machining operations. For the first time, this , ]! L2 a8 e- m1 p2 q6 p
book presents and explains the direct correlations between tool geometry and tool
) |4 M) g! n [& G/ V h7 `: a$ o9 R0 iperformance. The second reason is that I felt that there is no comprehensive book
( t+ w* y: ?3 n1 x& C4 ~" bon the subject so professionals, practitioners, and students do not have a text from
5 C, ?2 ^* X( C- m3 @' ~- Fwhich to learn more on the subject and thus appreciate the real value of tool + O8 ~% z/ X: L2 X h# `8 _8 p) @3 z. l
geometry. Finally, I wanted to share the key elements of tool geometry that I felt
* `' I4 u, p( }were not broadly understood and thus used in the tool design practice and in 3 b/ r0 m9 I, H* r& ]+ n& K+ w. F. a7 [
optimization of machining operations in industry. Moreover, being directly
9 T2 H) W8 j1 k& }! M* einvolved in the launch of many modern manufacturing facilities equipped with / a" e$ i5 K. x
state-of-the-art high-precision machines, I found that the cutting tool industry is not 3 U+ a1 `7 r# y
ready to meet the challenge of modern metal cutting applications. One of the key
* E3 N' X9 X" n5 d3 N% u6 nissues is the definite lack of understanding of the basics of tool geometry of 0 _5 m3 r3 h# q3 S: p% m9 |9 q
standard and application-specific tools.
: a* K8 [/ Z& @$ P0 X5 Q1 JThe lack of information on cutting tool geometry and its influence on the : ?( z: Y, T' E4 O. Q
outcome of machining operations can be explained as follows. Many great findings
( x: q7 j6 \. B( g. e( Ion tool geometry were published a long time ago when neither CNC grinding
* `! q+ W! ?, u$ a5 l. @machines capable of reproducing any kind of tool geometry were available nor
" ]+ k- v) I6 X, Dwere computers to calculate parameters of such geometry (using numerical D% F* G2 W+ E
methods) common. Manual grinding using standard 2- and 3-axis simple grinding
/ q& j% P8 U& M- e9 Tfeatures was common so the major requirement for tool geometry was the simpler
& N) y$ L' R5 _4 D, N5 A1 T3 L4 Nthe better. Moreover, old, insufficiently rigid machines, aged tool holders and part
: r$ `5 c, z' ?& z5 |/ afixtures, and poor metal working fluid (MWF) selection and maintenance levered
2 X+ D# [( x: b, @" L6 |+ v3 Kany advancement in tool geometry as its influence could not be distinguished under
) {3 h3 k! K4 P3 dthese conditions. Besides, a great scatter in the properties of tool materials in the
( D2 u& n0 `6 F2 Ypast did not allow distinguishing of the true influence of tool geometry. As a result,
3 s8 P1 q. H' ?; c* @6 h; [6 istudies on tool geometry were reduced to theoretical considerations of features of
, ?- e' s- I# Y) e" N, E* i5 Z9 ?twist drills and some gear manufacturing tools such as hobs, shaving cutters,
' ], G7 x2 I! rshapers, etc.
) M8 k# X5 P, |% R0 [! Q7 FGradually, once mighty chapters on tool geometry in metal cutting and tool
$ f* v) `5 N* R% n7 }design books were reduced to sections of few pages where no correlation between 7 D# g/ C- z9 @$ d, o s
tool geometry and tool performance is normally considered. What is left is a
/ S8 Q: p, B m @: {general perception that the so-called “positive geometry” is somehow better than
v6 P1 y$ D* d# `) y' w“negative geometry.” As such, there is no quantitative translation of the word
- P1 H$ H9 H" d7 P5 @“better” into the language of technical data although a great number of articles
1 E" @# f4 L) c- q0 I |written in many professional magazines discuss the qualitative advantages of : `9 F' ?: b' o& S8 ?
“positive geometry.” For example, one popular manufacturing magazine article
& Y9 y* _! D) q6 Y6 n( Gread “Negative rake tools have a much stronger leading edge and tend to push 3 [$ G& v0 R5 \! c5 F% D" j( P
against the workpiece in the direction of the cutter feed. This geometry is less free
$ ^ v/ y5 g+ e- S3 Dcutting than positive rakes and so consumes more horsepower to cut.” Reading 0 Z# V. e! s3 k( x8 \/ b+ ?
these articles one may wonder why cutting tool manufacturers did not switch their / l1 g" Q* |7 I, S
tool designs completely to this mysterious “positive geometry” or why some of / i; E b9 b& G. Y( R$ R
them still investigate and promote negative geometry.
0 n# a) e2 E" B2 W" iDuring recent decades, the metalworking industry underwent several important 5 H& T' w$ T; ]5 ^5 {) ?
changes that should bring cutting tool geometry into the forefront of tool design
5 I- G1 C/ g Y. \- ~( eand implementation: |