Presentation_11_9_05.ppt Machining Process

Machining Processes
Group #3
Erica Velarde, Sean Clifton
David Pincus, Ruben Sosa

Typical Parts Made with These
Processes
 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
 Precision Casting
 Powder Metallurgy
 Powder Injection
 Molding
 Abrasive Machining
 Thread Rolling

The Turning Process
Using Engine Lathes
 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

Presentation_11_9_05.ppt Machining Process

Typical Lathe and Its Various Components

Lathe Components
 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
 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

Lathe Operations
 Form Tools
 Boring
 Drilling
 Parting
 Grooving
 Thread Cutting
 Knurling

Cutting Operations Performed on a Lathe

Above Left: Example of Boring Above Right: Example of Drilling
Below Left: Example of Thread Cutting Below Right: Example of Grooving

Types of Lathes
 Bench Lathes
 Special Purpose Lathes
 Tracer Lathes
 Automatic Lathes
 Automatic Bar Machines
 Turret Lathes
 Computer-Controlled Lathes

Things to Remember About
Machining Parts on Lathes
 Takes considerable amount of time
 High Production Costs
 Wastes Material
 Not as Economical as Forming or Shaping

Machining Processes
Boring, Drilling, Reaming, and Tapping

What is Boring
 Performed to enlarge a hole made previously.
 Used for circular internal profiles in hollow
workpieces

Boring Machines
 Small pieces – lathe
 Large pieces – boring
mill
 Horizontal vs Vertical
 Boring mills
 Perform various
operations: TURNING,
FACING, GROOVING,
CHAMFERING

Vertical Boring Mill
 Large pieces can be
machined on a vertical
mill

Jig Boring Machines
 Vertical machines
 High precision bearings
 Used to make jigs and
fixtures
 Being replaced by CNC
boring machines

Considerations
 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?
 Typical for assembly with fasteners
 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
 Burring on the bottom surface upon
breakthrough requires further machining
 Diameters of holes are usually oversize
 Quality of drill
 Thermal properties
 Reaming and honing improve dimensional
accuracy

Standard-Point Twist Drill
 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
 Step Drill
 Produces 2 or more different diameters
 Core Drill
 Makes an existing hole larger
 Counterboring & Countersinking
 Produce depressions on the surface to
accommodate the heads of screws/bolts

More Drill Types
 Center drill
 Produces small hole on the
end of a workpiece
 Spot drill
 Starts a hole at the desired
location
 Spade drill
 Removable bits, produces
large-diameter or deep
holes
 Higher stiffness (absence of
flutes)
 Straight-flute drill
 Gun drill

Trepanning
 Removes a disk to create a hole

Material-Removal Rate
 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

Considerations
 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
 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. Centering
2. Drilling
3. Boring
4. Reaming

Tapping
 Produces threads
 May be done by hand
or machine
 Chipless tapping is a
process of internal
thread rolling

Milling
 The Process of cutting away
material by feeding a
workpiece past a rotating
multiple tooth cutter.

Peripheral Milling
 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
 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
 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
 a.k.a- Up Milling
 The Direction of cutter rotation opposes the
feed motion.

Climb Milling
 a.k.a.- Down Milling
 The direction of cutter rotation is the same as
the feed motion.

Other Types of Milling
 Straddle Milling
 Form Milling
 Slotting and Slitting
 Uses circular cutters

Tool holders
 Arbor Cutters
 Mounted on an arbor
 Used in peripheral, face, straddle and form
milling.

Shank-Type Milling
 Cutter and shank are
one peice

Design and Operating Guidelines
 Basic cutters should be used as much as
possible.
 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
 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
 First Milling Machine
 Built in 1820 by Eli Whitney

Column-and-Knee type
 Most common milling machines.

Basic Components
 Work Table
 Saddle
 Knee
 Overarm
 Head

Bed Type
 Work table is mounted is mounted directly on
the bed.
 Not versatile
 High Stiffness
 Used for high production work

Other Milling Machines
 Planer-Type
 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
 Planning
 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
 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
 Broaching is a similar
technique to shaping
with a long multiple-
tooth cutter and is used
to machine internal an
external surfaces.

 Broaching is just as
effective as
 Boring
 Milling
 Shaping
 Reaming

 Broaching machines
are very expensive but
these machines yield a
very high quantity of
production runs.

 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
 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
 Fast
 They work smoothly
and efficiently even
under heavy-duty
operation. With normal
care these machines
are indestructible.

Circular sawing
 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

 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

 Types of cold
sawing
machines

Band saw
 Uses a flexible steel band with a toothed edge
 Workpieces are fed into the cutting edge on vertical
machines
 Can produce straight, irregular, or curved cuts

Friction sawing
 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
 Form cutting (form-milling)
 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 100-
lb, 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

 Gear shaping
 Cutters rotate in timed
relationship with the
workpiece
 Produces internal
gears, external gears,
and integral gear-pinion
arrangements

 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/gbm22e-
42e.html
References

 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/gbm22e-
42e.html

 http://www.ohiobroach.com
 http://www.broachingmachine.com/
 http://class.et.byu.edu/mfg130/processes/me
chanicalreduction.htm
 http://www.doringer.com

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