Three places we visited:
1. Garner Denver – 3rd place
2. McElroy – really nice park in back
3. Fiberpads
Notes:
CHAPTER 17
Metal Forming
 Stresses to plastically deform the metal are usually compressive
 Examples: rolling, forging, extrusion


Desirable mechanical properties:
 Low yield strength
 High ductility
These properties are affected by temperature:
 Ductility increases and yield strength decreases when work
temperature is raised
Bulk Deformation Processes
(a) Rolling and (b) forging
(c) Extrusion and (d) wire and bar drawing
Punch & Die VS Blanking
P&D = keep the thing punched out
Blanking = keep everything but what was punched out
Sheet Metalworking
(a) Bending and (b) deep drawing
(c) Shearing: (1) punch first contacting sheet and (2) after cutting
where Yf = flow stress, that is, the yield strength as a function of strain
Yf  K n
Average flow stress; and  = maximum strain during deformation process
K n
Yf 
1 n
Cold Working - room temperature
Advantages
 Better accuracy, closer tolerances
 Better surface finish
 Strain hardening increases strength and hardness
Disadvantages
 Higher forces and power required for deformation
 Starting work surfaces must be free of scale and dirt
Warm Working
- above room temperature but below recrystallization temperature .3 Tm
Advantages
 Lower forces and power than in cold working
 More intricate work geometries possible
 Need for annealing may be reduced or eliminated
Hot Working
temperatures above the recrystallization temperature = .5Tm
Advantages
 Lower forces and power required
 Metals that usually fracture in cold working can be hot formed
Disadvantages
 Lower dimensional accuracy
 Higher total energy required
 Poorer finish

Strain rate in forming is directly related to speed of deformation v
CHAPTER 18
BULK DEFORMATION
1. Rolling – slab or plate is squeezed between opposing rolls
2. Forging – work is squeezed and shaped between opposing dies
3. Extrusion – work is squeezed through a die opening, thereby taking the
shape of the opening
4. Wire and bar drawing – diameter of wire or bar is reduced by pulling it
through a die opening
Importance of bulk def
 In hot working, significant shape change can be accomplished
 In cold working, strength is increased during shape change
 Little or no waste
(a) Two-high, (b) three-high, (c) four-high
(d) Cluster mill, (e) tandem rolling mill
Rolled Threads > cut threads
CHAPTER 19
Advantages of Sheet Metal Parts
 High strength
 Good dimensional accuracy
 Good surface finish
 Relatively low cost
Three Major Categories of Sheet Metal Processes
1. Cutting
 Shearing to separate large sheets
 Blanking to cut part perimeters out of sheet metal
 Punching to make holes in sheet metal
2. Bending
 Straining sheet around a straight axis
3. Drawing
 Forming of sheet into convex or concave shapes

Three principal operations in press working that cut sheet metal:
 Shearing
 Blanking
 Punching
Shearing Operation
(a) Blanking - sheet metal cutting to separate piece (called a blank) from
surrounding stock, (b) punching - similar to blanking except cut piece is scrap,
called a slug
V-Bending - Low production, Performed on a press brake, and V-dies are
simple and inexpensive
Chapter 20 - Machining
Machining is Important
 Variety of work materials can be machined
 Most frequently used to cut metals
 Variety of part shapes and special geometric features possible:
 Screw threads
 Accurate round holes
 Very straight edges and surfaces
 Good dimensional accuracy and surface finish
Disadvantages
 Wasteful of material
 Chips generated in machining are wasted material
 At least in the unit operation
 Time consuming
 A machining operation generally takes longer to shape a given part
than alternative shaping processes

Most important machining operations:
 Turning
 Drilling
 Milling
1. Single-Point Tools
 One dominant cutting edge
 Point is usually rounded to form a nose radius
 Turning uses single point tools
2. Multiple Cutting Edge Tools
 More than one cutting edge
 Motion relative to work achieved by rotating
 Drilling and milling use rotating multiple cutting edge tools
Roughing vs. Finishing Cuts
 Roughing - removes large amounts of material from starting work
part
 Some material remains for finish cutting
 High feeds and depths, low speeds
 Finishing - completes part geometry
 Final dimensions, tolerances, and finish
 Low feeds and depths, high cutting speeds
Chip Thickness Ratio
to
r 
tc
where r = chip thickness ratio; to = thickness of the chip prior to chip formation; and
tc = chip thickness after separation
 Chip thickness after cut is always greater than before, so chip ratio is always
less than 1.0
Four Basic Types of Chip in Machining
1. Discontinuous chip ---Brittle work materials, Low cutting speeds, Large feed
and depth of cut, High tool-chip friction
2. Continuous chip --- Ductile work materials, High cutting speeds, Small feeds
and depths, Sharp cutting edge, Low tool-chip friction
3. Continuous chip with Built-up Edge (BUE) ---- Ductile materials,
Low-to-medium cutting speeds, Tool-chip friction causes portions of chip to
adhere to rake face, BUE forms, then breaks off, cyclically
4. Serrated chip ----- Semicontinuous - saw-tooth appearance, Cyclical chip
forms with alternating high shear strain then low shear strain , Associated
with difficult-to-machine metals at high cutting speeds

Coefficient of friction between tool and chip
F

N

Friction angle related to coefficient of friction as
  tan 
Shear stress acting along the shear plan
Fs

As
where As = area of the shear plane
t ow
As 
sin 

Shear stress  = shear strength S of work material during cutting
CHAPTER 21 - MACHINING OPERATIONS AND MACHINE TOOLS
Rotational - (a) cylindrical or disk-like shape
Nonrotational - (b) block-like and plate-like
CAPTER 22 - CUTTING TOOL TECHNOLOGY
3 Modes of tool failure
1. Fracture failure
 Cutting force becomes excessive and/or dynamic, leading to brittle
fracture
2. Temperature failure
 Cutting temperature is too high for the tool material
3. Gradual wear
 Gradual wearing of the cutting tool
Tool wear
Taylor Tool Life Equation
vTn = C
v = cutting speed; T = tool life; and n and C are parameters that depend on feed,
depth of cut, work material, tool material, and tool life criterion
Tool Life Criteria in Production – worst to least worst
1. Complete failure of cutting edge
2. Visual inspection of wear by the machine operator
3. Fingernail test across cutting edge
4. Changes in sound emitted from operation
5. Chips become stringy and difficult to dispose
6. Degradation of surface finish
7. Increased power
8. Workpiece count
9. Cumulative cutting time
TOOL Catagories
 Single point tools
 Used for turning, boring, shaping, and planing
 Multiple cutting edge tools
 Used for drilling, reaming, tapping, milling, broaching, and
sawing
Cutting fluid contaminates
-
tramp oil
garbage
small chips
molds, etc.