Metal Cutting

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FUNDAMENTALS FUNDAMENT ALS OF MET METAL AL CUTTING CUTTING CHAPTER CONTENTS 5.1 5.2 5.3 5.4 5.5 5.6 5.7 5.8 5.9 5.10

Overview of Machining  Mechanics of Machining  Cutting Forces Cutting Temperat emperature ure Tool Wear and Tool Life Cutting uids Surface Finish Cutting Tool Material Materialss Machinability  Selection of Cutting Conditions

5.1 OVERVIEW OF MACHINING Denitions  term applied to all material-removal processes  Machining :  Metal cutting : the process in which a thin layer of excess metal (chip (chip)) is removed by a  wedge-shaped single-point or multipoint cutting tool  with  with dened geometry from a workpiece , through a process of extensive plastic deformation

v v

work surface

    r     a      m      i     r     p  

machined surface

chip cutting tool

work surface

cut

feed motion

workpiece

direction of  direction feed motion

chip

tool machined surface

direction of primary motion

Close-up view of a turning operation in  which a thin layer of metal (chip (chip)) is removed from the work surface  of  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 both primary and and feed  feed motions.

Schematics of metal cutting process showing the basic terminology.

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Overview of Machining  v

Valery Marinov, Manufacturing Technology 

 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 undened tools 

Set-up of the grinding operation showing the workpiece, abrasive bonded wheel and the spray of burned chips v

Non-traditional processes :

machining with electrical, optical or chemical sources of energy 

Cutting operation performed by a ve-axis CO 2 laser

The place of machining operations      s     g     l     a     n     i      i     r      t     r     e      t     a      t     a      S    m

Metallurgical processes

Casting

Ê

Metal forming

Powder metallurgy

Material-removal processes

 Assembly

     t     r     n     a     i     o     p    -      t     c     e    u      l      d     g     n    o      i     r      S    p     s      l      t     a    c     u     n     d      i      F    o     r     p

Diagram showing the place of machining operations within the entire production cycle.

Machining operations are capable of producing more precise dimensions and smooth surface nishes than all other manufacturing processes. They are performed after other processes, which create the general shape of the parts. Machining then provides the nal geometry, dimensions and nish.