Tools
Manufacturing
Processes
Outline
Types of Tools
Tool Geometry
Cutting Fluids
Effects
Types
Tool Wear
Forms
Causes
Failure Modes
Critical Parameters
Horsepower Used
Operating Temperature
Feed and Speed
Tool Life
Types of Tools
Tool Geometry
Single Point Tools
Multiple Point Tools
Chip Breakers
Effects of Material on Design
Single Point Tools
Multiple Point Tools
Chip Breakers
Important Tool
Properties
- High hardness
- Resistance to abrasion, wear and
chipping of the cutting edge
- High toughness/impact strength
- High hardness at high
temperatures
- Resistance to bulk deformation
- Chemical stability (does not react
or bond strongly with the work
material
- High modulus of elasticity
(stiffness)
- Consistent tool life
- Proper geometry and surface finish
Tool Materials
- Carbon and medium-alloy
steels
- High-speed steels
- Cast-cobalt alloys
- Carbides
- Coated tools
- Alumina-based ceramics
- Cubic boron nitride
- Silicon-nitride-base ceramics
- Diamond
- Whisker-reinforced materials
Cutting Speeds of
Tool Materials
Cutting Fluids
Effects
-
coolant
lubricant
flushes chips
reduces oxidation of heated
surfaces
Types
- cutting oils
- emulsified oils
- chemical fluids
Cutting Fluid
Application
Flooding
- ≥ 3 gallons per minute per tool
Misting
- atomized fluids
- a health hazard (OSHA limit =
.2 mg/m3)
High Pressure Systems
- often applied through the tool
Tool Wear
Forms
- crater wear
- flank wear
- chipping
Causes
-
abrasion
adhesion
diffusion
plastic deformation
Crater Wear and
Flank Wear
Crater wear
Flank wear
Failure Modes
Fracture
Temperature Failure
Gradual Wear
Critical Parameters
Horsepower Used
Operating Temperature
Horsepower Used
Values of Unit Horsepower for
Various Work Materials
Material
Carbon
Steels
Cast
Irons
Aluminum
Brinell
Hardness
Unit Horsepower
hpu hp/(in3/min)
150-200
0.6
201-250
0.8
251-300
1.0
125-175
0.4
175-250
0.6
50-100
0.25
Operating Temperature
Feed and Speed
Speed – the rate at which the
tool point moves as it rotates
(in a lathe, the rate at which
the cutting point on the
workpiece rotates)
Feed – the rate at which the tool
is fed into/along the workpiece
Feed and Speed
V = πDN/12
V = surface cutting speed (ft/min)
D = diameter of rotating object (in.)
N = rotation rate (RPM)
Feed and speed
Example: Assume a high-speed steel saw with 100
teeth and a diameter of 6 inches is used to cut
aluminum. Determine the proper RPM and feed
rate.
V (HSS, aluminum) = 550-1000 ft/min [in table]
N = 12V/(πD) = 12(550-1000)/(π6)
= 350-637 RPM
Feed (aluminum, saw) = .006-.01 in/tooth [in table]
(.006-.01)100 teeth = .6-1in
(.6-1)350 RPM = 210-350 in/min
Start with the lowest values. They can be increased
so long as the finish is acceptable.
Tool Life
F. W. Taylor, 1907
Taylor Tool Life Equation
vTn = C
n )
vTn = C(Tref
Cutting Performance
How do we know if cutting
parameters are optimal?
1.
2.
3.
4.
5.
6.
Surface finish
Tool wear
Chip shape
Sound
Cutting time
Heat
Summary
Tools fail slowly with gradual wear or
suddenly with fracture
Cutting fluids help reduce the effects of
wear and temperature failure
The materials of the tool and the workpiece
affect the tool shape and life
Higher cutting speeds increase the
operating temperature and decrease tool
life
It is necessary to calculate proper feed and
speed to prevent excessive tool wear
The End
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