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					Common Machining Operations




                         Kalpakjian
Parts of an “Engine” Lathe




                             Kalpakjian
Watchmaker’s lathe                 Typical “Engine” Lathe




         www.ticktockpro.com                   www.blazingtech.net


   Turret Lathe                    Big “Engine” Lathe




           www.liberatorcrew.com
                                              www.bakerprovan.com.au
Really Big “Engine” Lathes




                                               www.practicalmachinist.com




    60 feet c-c
                  www.harrismachinetools.com
CNC Lathe: aka “Turning Center”

(carriage is mounted toward back, “upside down”)




                                   www.machineryvalues.com
Machining
Parameters




             DeGarmo
Machining: Turning
Depth of Cut = DOC = (Dbefore – Dafter) / 2

Cutting Speed = Speed of metal moving towards cutting tip
• Usually called “Surface Feet per Minute”, SFPM, SFM
• Each cutting tool & workpiece material combo has a max SFM for decent tool wear.
 HSS & alum: 800 SFM
 HSS & 1020 steel: 110 SFM
 HSS & 1090 steel: 80 SFM
 HSS & hard 4140: 30 SFM
 TC & 1020 steel: 1000 SFM
• SFM = r*w
       = D * RPM * (π/12)
       ≈ D * RPM / 4
• RPMmax = 4 * SFM / D
  (most useful machining formula)
   E.g., find RPM for turning
   2” dia. 1020 steel:
   RPM ≈ 4*110/2 = 220
• RPM may need to be less due to chatter!
• Most relations are similar
    for milling, but D=cutter dia.                                             Kalpakjian
Cutting
Forces




          DeGarmo
Orthoganal
Model
(2-force)




             DeGarmo
Orthoganal
Model
(2-force)




             DeGarmo
Chip formation: chip types




                                          DeGarmo




                             Kalpakjian
Merchant’s Model
(Simplified 2-force)




                       DeGarmo
Chatter
Vibrational resonance of entire machining system, especially workpiece-cutter.
Causes poor surface finish, fast tool wear, noise
Factors: stiffnesses of workpiece, cutter, machine
         cutting params: speed, feed, DOC
         cutter geometry: rake, clearances
Solutions:
  Change the cutting params
    esp. speed
 Increase stiffnesses




                                                                                 Kalpakjian
Heat rise in Cutting




                   Kalpakjian
Temperature of Cutting Tip




                             Kalpakjian/Vieregge
Temperature of Cutting Tip




                       Kalpakjian / Chao & Trigger
Max Temperatures of Cutting Materials




                                        Kalpakjian
Machining Time of Cutting Materials




                                      Kalpakjian/Sandvik
Coated Carbide Cutting Inserts:
The norm for production machining
 Layers are 2-10 microns thick:
 TiN: titanium nitride (low friction, gold appearance)
 TiCN: titanium carbonitride (wear resistance)
 Al2O3: Alumina (chemical stability, wear resistance)

 Tungsten Carbide substrate (~shock and wear resistance)    www.greenleafcorporation.com




                                                           www.moldmakingtechnology.com

                               Kalpakjian/Kennametal
Cutter Shape
and Geometry




               Kalpakjian
Machining Costs




                  Kalpakjian
References

DeGarmo: E.P. DeGarmo et al, Materials and Processes in Manufacturing, Wiley, 2003.
Kalpakjian: http://www.nd.edu/~manufact/index3.htm

				
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posted:7/7/2011
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