Fundamentals of Cutting

1
Fundamentals of Cutting

• South Bend lathe
• Chip Formation
• Chip Breakers
• Feeds and Speeds
• Tool Materials

• Tool Properties
• Tool Wear
• Surface Finishes
• Cutting Fluids
• CNC Lathes

2
South Bend Engine Lathe
3
Chip Formation

• Discontinuous Continuous Built up edge

4
Chip Breakers

• On the Cutting Tool
• In the Material
• Inclusions
• Sulfur

5
Speed, Feed, Depth of Cut
6
Speeds, Depth of Cut

• Depth of Cut
• Speed

7
Feed Rates
or
8
Cutting Time Considerations

• Material removal rate
• Time to Cut

9
Tool Materials

• High SpeedSteel (HSS)
• CoatedCarbideInserts

10
Tool Properties

• High Hardness
• Resist Abrasion
• Resist Chipping
• Hot Hardness
• Resist BulkDeformation (E)

• Chemical Stability
• Adequate Thermalproperties
• Consistent ToolLife
• Geometry

11
Tool Wear

• slow death mechanisms gradual wear on flanks,
  or rake face of tool (crater)
• abrasion, adhesion, diffusion, chemical
• sudden death mechanisms unpredictable,
  catastrophic failure
• brittle fracture, chipping, plastic deformation

12
Tool Life

• Taylor's Equation Surface Speed
• Variation in material hardness
• within piece and piece to piece
• Variation in tool material and geometry
• Vibrations
• Changing surface characteristics of workpiece

13
Tool Geometry
14
Surface Finishes

• Tool Geometry and Feed rate

15
Surface Finishes

• Surface Speed and Depth of Cut

16
Cutting Fluids

• Reduces Cutting Temperature
• dimensional stability
• reduces thermal tool wear
• Acts as Lubricant
• reduces forces and energy consumption

17
Cutting Fluids

• Flood Cooling
• lowers temperature
• reduces oxidation
• Mist Cooling
• Better Visibility
• gets to inaccessible areas

18
Effects of Coolants

• On workpiece
• cracking, staining, chemical attack
• On machines
• bearings and slideways
• On environment
• breathing apparatus, and disposal