fundamentals of metal...
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CHAPTER CONTENTS
65
5 FUNDAMENTALS OF METAL CUTTING
5.1 Overview of Machining5.2 Mechanics of Machining5.3 Cutting Forces5.4 Cutting Temperature5.5 Tool Wear and Tool Life5.6 Cutting fluids5.7 Surface Finish5.8 Cutting Tool Materials5.9 Machinability5.10 Selection of Cutting Conditions
5.1 OVERVIEW OF MACHINING
Definitions
v Machining: term applied to all material-removal processes v Metal cutting: the process in which a thin layer of excess metal (chip) is removed by a wedge-shaped single-point or multipoint cutting tool with defined geometry from a workpiece, through a process of extensive plastic deformation
work surface
chip
cutting tool
feed motion
prim
ar
ym
otion
machinedsurface
Close-up view of a turning operation in which a thin layer of metal (chip) is
removed from the work surface of a rotating workpiece by a coated cemented carbide cutting tool. The newly generated surface
is referred to as a machined surface. Cutting process requires both primary and feed
motions.
direction of primary motion
direction offeed motion
workpiece
chip
toolcut
work surface
machined surface
Schematics of metal cutting process showing the basic terminology.
Overview of Machining66 Valery Marinov, Manufacturing Technology
v Abrasive processes: material removal by the action of hard, abrasive particles that are usually in the form of a bonded wheel. Each single particle acts like a single-point cutting tool. Since the particular geometry of a particle is not known, abrasive processes are referred to as machining with geometrically undefined tools
v Non-traditional processes: machining with electrical, optical or chemical sources of energy
Set-up of the grinding operation showing the workpiece, abrasive bonded wheel and the spray of burned chips
Cutting operation performed by a five-axis CO
2 laser
The place of machining operations
Metallurgical processes
Casting Metal forming Powder metallurgy
Material-removal processes
Assembly
Sing
le-p
art
prod
uctio
nFi
nal
prod
ucts
Star
ting
mat
eria
ls
Ê
Diagram showing the place of machining operations within the entire production cycle.
Machining operations are capable of producing more precise dimensions and smooth surface finishes than all other manufacturing processes. They are performed after other processes, which create the general shape of the parts. Machining then provides the final geometry, dimensions and finish.