Machining Processes
Group #3
Erica Velarde, Sean Clifton
David Pincus, Ruben Sosa
Typical Parts Made with These
Processes
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Machine Components
Engine Blocks and Heads
Parts with Complex Shapes
Parts with Close Tolerances
Externally and Internally Threaded Parts
Products and Parts Made By These
Processes
Alternative Processes
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Precision Casting
Powder Metallurgy
Powder Injection
Molding
Abrasive Machining
Thread Rolling
The Turning Process
Using Engine Lathes
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Operate on all Types of
Materials
Use of single-point tools
Skilled Labor
Low Production Rate
Tool Geometry
Rake Angle
 Side Rake Angle
 Cutting-Edge
Angle
 Relief Angle
 Nose Radius
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Typical Lathe and Its Various Components
Lathe Components
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Bed: Usually made of cast iron. Provides a heavy
rigid frame on which all the main components are
mounted.
• Ways: Inner and outer guide railsn that are
precision machined parallel to assure accuracy of
movement.
• Headstock: mounted in a fixed position on the
inner ways, usually at the left end. Using a chuck, it
rotates the work.
• Gearbox: inside the headstock, providing multiple
speeds with a geometric ratio by moving levers.
• Spindle: Hole through the headstock to which bar
stock can be fed.
• Chuck: 3-jaw (self centering) or 4-jaw (independent)
to clamp part being machined.
• Tailstock: Fits on the inner ways of the bed and can
slide towards any position the headstock to fit the
length of the work piece. An optional taper turning
attachment would be mounted to it.
• Tailstock Quill: Has a Morse taper to hold a lathe
center, drill bit or other tool.
• Carriage: Moves on the outer ways. Used for
mounting and moving most the cutting tools.
• Cross Slide: Mounted on the traverse slide of the
carriage, and uses a handwheel to feed tools into
the workpiece.
• Tool Post: To mount tool holders in which the cutting
bits are clamped.
• Compound Rest: Mounted to the cross slide, it
pivots around the tool post.
• Apron: Attached to the front of the carriage, it has
the mechanism and controls for moving the carriage
and cross slide.
• Feed Rod: Has a keyway, with two reversing pinion
gears, either of which can be meshed with the
mating bevel gear to forward or reverse the carriage
using a clutch.
• Lead Screw: For cutting threads.
• Split Nut: When closed around the lead screw, the
carriage is driven along by direct drive without using
a clutch.
• Quick Change Gearbox: Controls the movement of
the carriage using levers.
• Steady Rest: Clamped to the lathe ways, it uses
adjustable fingers to contact the workpiece and align
it. Can be used in place of tailstock to support long
or unstable parts being machined.
• Follow Rest: Bolted to the lathe carriage, it uses
adjustable fingers to bear against the workpiece
opposite the cutting tool to prevent deflection.
Lathe Accessories
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Carriage and Cross Slide Stops
Devices for Turning Parts with Various Tapers
Milling, Sawing, Gear-Cutting, and Grinding
Attachments
Various Attachments for Boring, Drilling, and
Thread Cutting
Typical Lathe and Its Various Components
More Tool Geometry
Lathe Operations
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Form Tools
Boring
Drilling
Parting
Grooving
Thread Cutting
Knurling
Cutting Operations Performed on a Lathe
Above Left: Example of Boring
Below Left: Example of Thread Cutting
Above Right: Example of Drilling
Below Right: Example of Grooving
Types of Lathes
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Bench Lathes
Special Purpose Lathes
Tracer Lathes
Automatic Lathes
Automatic Bar Machines
Turret Lathes
Computer-Controlled Lathes
Turret Lathe
Computer-Controlled Lathe
Things to Remember About
Machining Parts on Lathes
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Takes considerable amount of time
High Production Costs
Wastes Material
Not as Economical as Forming or Shaping
Machining Processes
Boring, Drilling, Reaming, and Tapping
Boring and Boring Machines
What is Boring
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Performed to enlarge a hole made previously.
Used for circular internal profiles in hollow
workpieces
Boring Machines
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Small pieces – lathe
Large pieces – boring
mill
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Horizontal vs Vertical
Boring mills
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Perform various
operations: TURNING,
FACING, GROOVING,
CHAMFERING
Horizontal Boring Mill
Vertical Boring Mill
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Large pieces can be
machined on a vertical
mill
Jig Boring Machines
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Vertical machines
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High precision bearings
Used to make jigs and
fixtures
Being replaced by CNC
boring machines
Considerations
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Through holes, rather than blind holes,
should be specified.
Smaller length-bore diameter ratios
Interrupted internal surfaces should be
avoided.
Drilling, Drills, and Drilling
Machines
What are Holes used For?
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Typical for assembly with fasteners
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i.e. screws, bolts, rivets
Weight reduction
Ventilation
Access to inside parts
Appearance
Drilling is a Common Process!!!
THE COST OF HOLE MAKING IS AMONG THE
HIGHEST MACHINING COSTS IN
AUTOMOTIVE ENGINE PRODUCTION
Properties
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Burring on the bottom surface upon
breakthrough requires further machining
Diameters of holes are usually oversize
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Quality of drill
Thermal properties
Reaming and honing improve dimensional
accuracy
Standard-Point Twist Drill
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Point angle (118-135deg)
Lip-relief angle (7-15deg)
Chisel-edge angle (125-135deg)
Helix angle (15-30deg)
Diameter range from 0.5-150mm
Other Types of Drills
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Step Drill
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Core Drill
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Produces 2 or more different diameters
Makes an existing hole larger
Counterboring & Countersinking
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Produce depressions on the surface to
accommodate the heads of screws/bolts
More Drill Types
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Center drill
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Spot drill
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Starts a hole at the desired
location
Spade drill
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Produces small hole on the
end of a workpiece
Removable bits, produces
large-diameter or deep
holes
Higher stiffness (absence of
flutes)
Straight-flute drill
Gun drill
Gun Drill
Trepanning
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Removes a disk to create a hole
Material-Removal Rate
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MRR=(pi*D^2)f*N / 4
Pi*D^2 / 4= cross sectional area
F = the distance penetrated per revolution
N = rotational speed
General Troubleshooting
Problem
Probable causes
Drill breakage
Dull bit, chips clogging flutes, feed to
high, lip relief angle too small
Excessive drill wear
Cutting speed to high, ineffective fluid,
rake angle too high, drill burned when
sharpened
Tapered hole
Drill misaligned or bent, lips not equal
Oversize hole
Same as above, machine spindle loose,
chisel edge not central, side force on
workpiece
Poor hole surface finish
Dull bit, ineffective fluid, welding of
workpiece on drill margin, improperly
ground drill, improper alignment
Reaming and Reamers
Considerations
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Drilling should be perpendicular to the surface
Interrupted holes should be avoided
Hole bottoms should match standard drill point
angles
Through holes preferred to blind holes
Preexisting holes or dimples help center the drill
Blind holes must be drilled deeper than subsequent
reaming or tapping operations
What is Reaming
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An operation used to make an existing hole
dimensionally more accurate and/or to
improve surface finish
For further accuracy and surface finish, holes
may be burnished, ground or honed.
4 Steps to Accuracy
1.
2.
3.
4.
Centering
Drilling
Boring
Reaming
Tapping and Taps
Tapping
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Produces threads
May be done by hand
or machine
Chipless tapping is a
process of internal
thread rolling
Milling and Milling Machines
Milling
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The Process of cutting away
material by feeding a
workpiece past a rotating
multiple tooth cutter.
Types of Milling
Peripheral Milling
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Peripheral Milling is when the cutter is longer than
the width of the cut.
a.k.a.- Slab Milling
The axis of the cutter is usually parallel to the work
piece surface.
Face Milling
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the cutter is mounted on a spindle having an
axis of rotation perpendicular to the
workpiece surface.
Leaves feed marks on the machined surface.
End Milling
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The cutter generally rotates on an axis
vertical to the workpiece.
It can be tilted to machine tapered surfaces.
Cutting teeth are located on both the end
face of the cutter and the periphery of the
cutter body.
Can produce a variety of surfaces at any
depth.
Conventional Milling
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a.k.a- Up Milling
The Direction of cutter rotation opposes the
feed motion.
Climb Milling
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a.k.a.- Down Milling
The direction of cutter rotation is the same as
the feed motion.
Other Types of Milling
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Straddle Milling
Form Milling
Slotting and Slitting
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Uses circular cutters
Tool holders
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Arbor Cutters
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Mounted on an arbor
Used in peripheral, face, straddle and form
milling.
Shank-Type Milling
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Cutter and shank are
one peice
Design and Operating Guidelines
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Basic cutters should be used as much as
possible.
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Avoid expensive special cutters.
•Chamfers should be specified instead of
radii.
•Chamfer-A furrow or groove, as in a column.
•Avoid internal cavities and pockets with sharp
corners.
•Due to the difficulty of doing them.
Troubleshooting
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Tool Breakage
Tool material lacks toughness,
improper angles.
Excessive Tool Wear
improper tool material, improper
tool fluids.
Rough Surface Finish
Feed per tooth too high, tool
chipped or worn.
Chatter Marks
Insufficient stiffness of system,
external vibrations.
Breakout
Lead angle too low, feed and
depth of cut too high.
Milling Machines
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First Milling Machine
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Built in 1820 by Eli Whitney
Column-and-Knee type
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Most common milling machines.
Basic Components
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Work Table
Saddle
Knee
Overarm
Head
Bed Type
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Work table is mounted is mounted directly on
the bed.
Not versatile
High Stiffness
Used for high production work
Other Milling Machines
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Planer-Type
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Several heads and cutters able to mill different surfaces
•Rotary-Table
•One or more heads for face milling.
•Computer Numerical Control
•Able to mill, drill, bore and tap with repetitive accuracy
•Profile Milling Machines
•5 axes of movement.
Planning and Shaping
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Planning
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Large workpieces 25m X 15m
Work piece is mounted on a table and travels back and
forth along a straight path.
Cutting speeds can get up to 120 m/min with 150 hp
Shaping
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Tool does the moving
Small less than 1m X 2m
introduction
Broaching
and Broaching machines
Sawing
Filing
Gear
Manufacturing by Machining
Broaching and Broaching machines
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Broaching is a similar
technique to shaping
with a long multipletooth cutter and is used
to machine internal an
external surfaces.
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Broaching is just as
effective as
Boring
Milling
Shaping
Reaming
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Broaching machines
are very expensive but
these machines yield a
very high quantity of
production runs.
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Uses a single pass
for finished shapes
or sized
Produces close
tolerances and good
surface finish
Uses a multipoint
cutting tool (broach)
Has the roughing
and finishing teeth
on the same tool
Sawing
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Sawing is an old common operation dating back to
around 1000 B.C
Sawing is an efficient bulk removal process and can
produce near net shape materials
The process wastes little material
Most common use of saws
 Hacksaws
 Circular saws
 Band saws
 Friction sawing
Samples of various sawing operations
Hacksaws
Hacksaws were developed in the 1960’s.
 Good for cutting off bars, rods, and structural
shapes
Power hacksaws
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Fast
They work smoothly
and efficiently even
under heavy-duty
operation. With normal
care these machines
are indestructible.
Circular sawing
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Circular sawing is a multipoint cutting process in
which a circular tool is advanced against a stationary
workpiece to sever parts or produce narrow slots.
Uses thin circular blades with teeth on periphery
Rotating blade is fed into a stationary workpiece
Produces a narrow cut and a good surface finish
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Circular saws also
called cold saws when
cutting metal
They are used for high
production rate sawing
Cold sawing is used in
industry very commonly
particularly for cutting
large crossed sections.
Diamond Saw Blades For Marble
And Limestone
saw blade
for plastics
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Types of cold
sawing
machines
Band saw
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Uses a flexible steel band with a toothed edge
Workpieces are fed into the cutting edge on vertical
machines
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Can produce straight, irregular, or curved cuts
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Friction sawing
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Workpieces are fed into
a continuously moving
band
Produces fine, accurate
work
Is a finishing operation
in which small amounts
of material are removed
Gear Manufacturing by Machining
Several processes for making gears
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Form cutting (form-milling)
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Gear generating (Hobbing, Shaping)
Gear milling
 Uses a rotating form
cutter
 Gear blanks are
indexed after each cut
 Is a low production
process
 Gear teeth are
produced individually
Gear generating
 This particular machine
removes over 17 lb of
8822 steel from a 100lb, 18-in.-diameter gear
in under 12 min
Gear Hobbing
 Is a gear generating
process that uses a
helical hob cutter
 Cuts several teeth on a
progressive basis
 Is used for high
production runs
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Gear shaping
Cutters rotate in timed
relationship with the
workpiece
Produces internal
gears, external gears,
and integral gear-pinion
arrangements
References
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http://www.manufacturingcenter.com/tooling/archive
s/0604/0604cooling.asp
http://www.mfg.mtu.edu/marc/primers/milling/
http://www.americanmachinetools.com/How_to_use
_a_Milling_Machine_files/Fig8-33.gif
http://www.advantagefabricatedmetals.com/images/
slittingprocess.gif
http://www.eliwhitney.org/inventor.htm
http://www.cncmasters.com/images/bps-1649.jpg
http://www.lagun.com/products/gbm/gbm22e42e.html
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http://www.manufacturingcenter.com/tooling/archive
s/0604/0604cooling.asp
http://www.mfg.mtu.edu/marc/primers/milling/
http://www.americanmachinetools.com/How_to_use
_a_Milling_Machine_files/Fig8-33.gif
http://www.advantagefabricatedmetals.com/images/
slittingprocess.gif
http://www.eliwhitney.org/inventor.htm
http://www.cncmasters.com/images/bps-1649.jpg
http://www.lagun.com/products/gbm/gbm22e42e.html
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http://www.ohiobroach.com
http://www.broachingmachine.com/
http://class.et.byu.edu/mfg130/processes/me
chanicalreduction.htm
http://www.doringer.com