ISE 311 Machining I Lab in conjunction with Chapters 21, 22, and 23 in the text book Fundamentals of

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ISE 311Machining I Labin conjunction
withChapters 21, 22, and 23 in the text
bookFundamentals of Modern ManufacturingThird
EditionMikell P. GrooverApril 17th, 2008
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Outline

• Introduction
• Basic Principles of Machining
• Background Information on Drilling, Turning and
  Other operations related to them
• Objectives of the Lab
• Overview of Lab Materials and Equipment Used
• Demonstration of Machining Drilling, Facing,
  and Turning Pictures
• Summary

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Introduction Basic Principles of Machining

• Machining is a manufacturing process in which a
  cutting tool is used to remove excess material
  from a workpiece. The material that remains is
  the desired part geometry. The cutting tool
  deforms the workpiece in shear and creates scrap
  called chips. As chips fall off the workpiece a
  new surface is exposed.

A schematic showing a simple machining process
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Introduction Basic Principles of Machining

• Almost all solid metals, plastics, and composites
  can be machined by conventional machining.
• Machining can create any regular geometry, i.e.,
  planes, round holes, and cylinders.
• Machining can produce dimensions to tolerances of
  less than 0.001 (0.025mm)
• Surface finishes of better than 16µin (0.4 µm)
  can be produced by machining processes.

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Introduction Basic Principles of Machining

• A cutting tool has one cutting edge (facing tool
  or turning tool) or more than one cutting edges
  (drill, end mill). The cutting edge separates the
  chip from the workpiece.
• The rake face of a tool guides the chip from the
  surface of the workpiece and is oriented at an
  angle a. The rake angle a is measured relative to
  a plane perpendicular to the work surface.
• The flank of a tool provides clearance between
  the cutting tool and the newly exposed surface to
  protect the surface from abrasion. The flank is
  oriented at an angle called the relief angle.
• The picture below illustrates the make-up of a
  cutting tool.

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Machining I Basic Principles of Machining

• The three most common types of conventional
  machining processes are
• Drilling
• Turning
• Milling
• Other conventional machining processes include
• Shaping
• Planing
• Broaching
• Sawing
• Grinding

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Machining I Drilling

• Drilling is used to create round holes in
  workpieces using a rotating tool with two cutting
  edges. This rotating tool is called a drill or
  drill bit. This operation is normally performed
  on a drill press.
• Two types of holes can be made
• through holes, in which the drill exits the
  opposite side of the work
• blind holes , in which the drill does not exit

Figure depicting (a) through holes and (b) blind
holes
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• The figure below depicts a twist drill the most
• commonly used drill bit.

Twist drill bit
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Machining I Drilling

• The body of a twist drill has two spiral flutes
  which usually have a 30 helical angle. These
  flutes act as a passageway for chip extraction
  from the hole and for coolant to enter the hole
  (however, cooling is not effective since chips
  and coolant move in opposite directions).
• The thickness of the drill between the flutes,
  also called the web, provides support over the
  length of the drill body.
• The point of the twist drill is in the shape of a
  cone and the point angle is typically 118.

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Machining I Drilling

• The twist drill is fed into the workpiece while
  rotating and the relative motion between the
  cutting edges of the drill and the workpiece
  results in material removal and, hence, chip
  formation.
• The flutes provide enough clearance to allow the
  chips to be extracted. During drilling, however,
  friction between the chip and cutting surface
  (rake face) as well as between the outer diameter
  of the drill and workpiece generates a large
  amount of heat and, thus, the temperature of the
  workpiece and drill increases dramatically.

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Machining I Drilling

• Drills are limited to a depth of no greater than
  4 times its diameter because of the high
  temperature and the high load on the drilling
  bit, which
• Decreases the strength of the drill and makes it
  easier to break.
• Negatively affects the surface finish of the
  hole.
• Increases the deflection in the drill, which
  affects the straightness and dimensional accuracy
  of the hole

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Machining I Drilling

• To solve the temperature rise problem, the
  following is
• common
• Peck drilling the drill is periodically
  withdrawn from the hole to clear chips
• Some drills have internal holes in the drill body
  through which cutting fluid is delivered to the
  cutting interface.
• Increasing flute size makes it easier to clear
  chips from
• the hole but results in smaller web thickness and
  affects
• the drill rigidity (the opposite is also true).

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Machining I Drilling

• Prior to drilling, centering (or center drilling)
  is used to create a starter hole (using a center
  drill). This is used to
• Define the location of the hole.
• Solve the Walking or Wandering problem which
  happens because of drill deflection before the
  chisel penetrates the workpiece.

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Machining I Drilling

• The following operations are all related to
  drilling and can be performed once a hole has
  been created
• Reaming a reamer (usually with multiple straight
  flutes) is used to ream a hole, i.e., slightly
  enlarge a hole and improve its surface finish and
  provide tighter tolerances.
• Tapping a tap is used to create internal screw
  threads on an existing hole.
• Counterboring generates a stepped hole, i.e., a
  larger diameter hole is created over a smaller
  diameter hole. This process is used to seat bolt
  heads below the surface of a workpiece or flush
  with the surface.

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Machining I Drilling

• Operations related to drilling (continued)
• Countersinking is similar to counterboring, but
  the hole step is conical and is used for flat
  head screws. Countersinking is used also for
  deburring.
• Spotfacing is similar to milling. This process is
  used to provide a flat surface on the workpiece.

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Machining I Drilling

• The figure below illustrates the various
  operations related to drilling.

• Reaming
• Tapping
• Counterboring
• Countersinking
• Center drilling
• Spot facing

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Machining I The Drill Press

• The drill press is the most commonly used machine
  tool for drilling and the related operations
  mentioned previously. The most common drill
  press, and also the one used in the lab
  procedure, is the upright drill press. The base
  sits on the floor, has a table for holding the
  workpiece, a head with a powered spindle for the
  cutting tool, and a bed and column for support.

Figure showing upright drill press
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Machining I Turning and Facing

• Turning is a machining process performed on a
  lathe in which a single point tool removes
  material from a rotating cylindrical workpiece.
  The cutting tool is fed linearly and in a
  direction parallel to the axis of rotation of the
  workpiece as shown in the figure below.
• NOTE
• In drilling, the cutting tool rotates, while in
  turning the workpiece rotates.

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Machining I Turning and Facing

• The lathe provides the power to rotate the
  workpiece, feed the tool at the specified rate
  and cut the workpiece at the necessary depth.
  Other operations related to turning that can be
  accomplished by using a lathe include
• Facing the tool is fed radially into the
  rotating workpiece to create a new surface (face)
  on the end.
• Taper turning the tool is fed at an angle to the
  axis of rotation to create a conical geometry.
• Contour turning The tool follows a contour that
  is other than straight, thus creating a contoured
  form in the turned part.

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Machining I Turning and Facing

• Other operations related to turning (continued)
• Form turning a formed cutting tool is fed into
  the workpiece radially
• Chamfering the cutting tool cuts an angle on the
  corner of the cylinder. A very small chamfer can
  be used to remove burrs usually formed during
  machining processes and to eliminate sharp
  corners (for safety reasons).
• Cutoff (or parting) the tool is fed radially
  (like facing) at some length along the workpiece
  to cut off the end of the part

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Machining I Turning and Facing

• Other operations related to turning (continued)
• Threading a pointed tool is fed linearly across
  the outside diameter of the workpiece (similar to
  turning) at a large feed creating external
  threads on the cylinder
• Boring a tool is fed linearly and parallel to
  the axis of rotation to correct a previously
  drilled hole and/ or to enlarge the diameter of
  an existing hole in the part
• Drilling drilling can be performed on a lathe by
  feeding the drill into the rotating part along
  its axis.
• Knurling a knurling tool produces a
  cross-hatched pattern on the outer diameter of
  the workpiece

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Machining I Turning and Facing

• The figure below displays operations related to
  turning

• Facing
• Taper turning
• Contour turning
• Form turning
• Chamfering
• Cutoff
• Threading
• Boring
• Drilling
• Knurling

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Machining I The Lathe

• The engine lathe is a manually operated machine
  tool which is widely used in low to medium
  production. Initially, these machine tools were
  powered by steam engines, hence the term engine
  lathe.

The figure to the left shows the principal
components of an engine lathe. The drive unit
used to rotate the spindle is enclosed in the
headstock. The spindle rotates the workpiece. The
tailstock is occasionally used to support one end
of the workpiece.
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Machining I The Lathe

• The cutting tool is held in the tool post. The
  tool post is mounted on the cross-slide. The
  cross-slide is mounted on the carriage. The
  carriage slides along the ways. The ways are
  built into the bed of the lathe.
• The carriage moves in a direction parallel to the
  axis of rotation and controls the feed rate of
  the tool. The cross-slide feeds perpendicular to
  the workpiece. Thus, by moving the carriage, a
  turning operation can be performed by moving the
  cross-slide a facing operation can be carried out.

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Machining I The Lathe

• The size of a lathe is determined by its swing
  and maximum distance between centers.
• The swing of a lathe is the maximum diameter of
  the workpiece that can be rotated in the spindle.
  This diameter is determined as twice the distance
  from the axis of rotation to the ways of the
  machine.
• The maximum distance between centers is the
  maximum length of a workpiece that can be mounted
  between the centers of the headstock and
  tailstock.

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Machining I The Lathe

• There are 4 common methods to hold the workpiece
  in a lathe as shown in the figure below (a)
  mounting between centers, (b) chuck, (c) collet,
  and (d) face plate.

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Machining I The Lathe

• When mounting the work between the centers, one
  end of the workpiece is held in place by the
  headstock and the other end is supported by the
  tailstock. This method is used for long parts
  with relatively small diameters.
• The chuck (shown to the right) utilizes either
  three or four jaws to hold the workpiece by its
  outside diameter. Some jaws are manufactured in a
  way such that they can hold a tubular workpiece
  by the inside diameter.

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Machining I The Lathe

• A collet (shown below) has a tubular bushing with
  slits over half of its length. These slits allow
  the collet to be squeezed to reduce its diameter
  and grasp the cylindrical workpiece. Collets must
  be made in many various sizes to match the
  diameter of the workpiece since there is a limit
  to the amount the diameter of the collet can be
  reduced.

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Machining I The Lathe

• A face plate is mounted onto the spindle and is
  used to hold workpieces with non-cylindrical
  shapes. The face plate is equipped with custom
  designed clamps which are manufactured
  specifically to a particular application.

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Machining I Cutting Parameter in turning

• The three cutting parameters in turning are (see
  the figure
• below)
• The cutting speed v (ft/min) the tangential
  speed
• The depth of cut d (in) the penetration of the
  cutting tool below the original surface of the
  work.
• The feed f (in/rev) distance (parallel to the
  axis of rotation) traveled by the tool per one
  revolution of the work

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Machining IRequired Calculations for this lab

• The following applies for both turning and
  drilling
• Look for v and f in tables
• To calculate the spindle RPM (rev/min) from v
  (ft/min), use the following equation
• 
  
• The Material Removal Rate RMR (in3/min) is the
  volume of material removed (in3) divided by time
  (min)

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Machining IRequired Calculations for this lab

• Machining power, P, is the energy per unit time
  required to perform a machining operation
  (usually in Horse Power, HP)
• 1 HP 33, 000 lbft/min
• Unit Power Pu or Specific Energy U is the power
  divided by the Material Removal Rate
• For each material, there is an approximate value
  of the Unit Power. Look for Pu in tables.
• To calculate P

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Machining ITool materials

• The most important properties in tool materials
  are
• Toughness
• Hot Hardness
• Wear resistance
• There is always a trade-off between these
  properties. For example, increasing the hot
  hardness and wear resistance of the cutting tool
  generally results in a reduction in toughness.
• High Speed steel (HSS) tools are the most common
  and will be used in this lab.

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Lab Objectives

• This lab has the following objectives
• Become familiar with basic lathe and drill press
  operations
• Get firsthand experience at trying to maintain
  tolerances in machining
• Learn to calculate cutting speed, material
  removal rate, and spindle horsepower

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Lab Safety

• Everyone MUST wear approved safety glasses
• Remove or secure anything which might become
  caught in rotating machinery.
• Remove all jewelry from the hands and wrists.
  Remove necklaces that will dangle when stooped
  over.
• Short sleeves are recommended roll long sleeves
  up to the elbow.
• Loose clothing is not advised. Very baggy shirts,
  sweaters, sweatshirts, etc. are not allowed.
  Unbuttoned shirts or jackets are not allowed.
• Secure long hair. When looking down at the
  ground, if your hair hangs more than 4 beyond
  your nose, you need to secure it.
• Do not touch rotating tools or chips clinging to
  rotating tools.
• Exercise extreme care when touching chips they
  are very sharp and can be very hot.

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Lab Procedure Part A

• You will need to use the drill press and perform
  drilling operations in order to make the bracket.
• The equipment you will use in this part includes
• Scribe
• Drill press
• Center drill
• 2 drill bits
• Reamer
• Counterbore tool
• Countersink tool

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Lab Procedure Part A
Speed adjustment
Head
Forward/Reverse lever
Spindle
Column
Chuck
Table
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Lab Procedure Part A
0.375 Reamer
23/64 Drill
Counterbore tool
Countersink tool
Center Drill
7/32 Drill
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Lab Procedure Part A

• Procedure (refer to the drawing in appendix A)
• Using the scribe, mark the locations of the holes
  to be drilled on the workpiece. Make sure to set
  the correct measurement on the scribe using a
  scale. Refer to the drawing in appendix A for the
  correct dimensions.

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Lab Procedure Part A

• Procedure (refer to drawing in appendix A)
• Once the center lines for the 3 holes have been
  marked, clamp the workpiece in the holder on the
  drill press.
• Locate the center drill in the chuck and, without
  turning the drill press on, manually align the
  center drill to one of the cross hairs that are
  inscribed on the workpiece
• NOTE
• DO NOT attempt to drill the workpiece
• with the drill press in the reverse position!
• NEVER adjust the speed while the
• machine is off!

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Lab Procedure Part A

• Procedure (refer to drawing in appendix A)
• Once the center drill is aligned, return it to
  its home position. Turn the drill press on by
  moving the lever to FORWARD and then adjust the
  speed as stated in appendix A. Apply lubricant as
  necessary.
• Hold the workpiece in place with your left hand
  and with your right hand bring the center drill
  down to the surface of the workpiece.
• Slowly create a starter hole. Once a hole has
  been created return the drill press to its
  starting position and turn the machine off.
• Repeat step 3 for the remaining 2 holes. The
  speed will remain the same. Apply lubricant, if
  necessary.

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Lab Procedure Part A
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Lab Procedure Part A

• Procedure (refer to drawing in appendix A)
• Remove the center drill once all three starter
  holes have been created and replace it with the
  23/64 drill.
• With the drill press off, manually align the
  drill bit with the middle hole.
• Turn the machine to FORWARD, adjust the speed
  accordingly, and apply the lubricant as
  necessary. Drill a through hole and return the
  drill press to its home position.

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Lab Procedure Part A

• Procedure (refer to drawing in appendix A)
• Remove the 23/64 drill bit from the chuck and
  insert the 3/8 reamer.
• Turn the machine on, adjust the speed, apply the
  lubricant and ream the 0.360 hole to 0.375.
  Turn off the drill press. Note If the tool
  holder was not moved, you do not need to manually
  align the cutting tool in this step.

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Lab Procedure Part A

• Procedure (refer to drawing in appendix A)
• Remove the reamer and insert the 7/32 drill into
  the chuck. Manually align the drill to the center
  of one of the outside holes.
• Once aligned, turn on the drill press, adjust the
  speed, apply the lubricant, and drill a through
  hole. Once the through hole has been drilled,
  turn off the machine.
• Repeat step 15 for the third and final hole.

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Lab Procedure Part A

• Procedure (refer to drawing in appendix A)
• Remove the 7/32 drill and place the counterbore
  tool into the chuck.
• Manually align the counterbore tool with one of
  the outside holes. Turn on the drill press,
  adjust the speed, apply the lubricant, and drill
  a blind hole approximately 3/8 deep.

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Lab Procedure Part A

• Procedure (refer to drawing in appendix A)
• Turn off the drill press. Remove the counterbore
  tool and insert the countersink tool into the
  chuck.
• Manually align the countersink tool with the
  third hole. Turn on the drill press, apply the
  lubricant, and drill a countersink hole.

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Lab Procedure Part A

• Procedure (refer to drawing in appendix A)
• If time permits, deburr the bottom face of the
  bracket using the countersink tool. Align the
  countersink tool with each of the three holes
  that have been drilled and remove only enough
  material to remove the burrs created by drilling.

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Lab Procedure Part B

• You will need to use the engine lathe to perform
  facing, turning, drilling, and tapping operations
  in order to make the shaft.
• The equipment you will use in this part includes
• Engine lathe
• Facing tool
• Turning tool
• Center drill
• Drill
• Tap

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Lab Procedure Part B
Chuck
Tool post
Headstock
Tailstock
Spindle speed selector
Cross slide
Cross feed handwheel
Feed selector
Feed handwheel
Ways
Lead screw
Bed
On/Off levers
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Lab Procedure Part B
Facing tool
Tap
Turning tool
Tap holder
Tap guide
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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Insert and secure the workpiece into the collet
  (or chuck).
• Turn on the lathe by lifting on the lever.
• Rotate the wheel that controls the feed
  counterclockwise and place the tool in line with
  the workpiece.
• While holding the feed to prevent it from moving,
  rotate the cross feed in a clockwise direction to
  face the workpiece. Bring the cross feed back to
  its starting position after completing the facing
  operation.
• Repeat this facing process 1 or 2 more times by
  slightly feeding the tool to make sure that a
  flat surface has been generated.
• NOTE
• NEVER power on the lathe if the tool is in
  contact with the workpiece

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Lab Procedure Part B
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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Remove the facing tool and insert the turning
  tool. Adjust the feed stop to 3/8 from the
  initial position.

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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Turn on the lathe and cross feed the tool. Once
  the tool slightly touches the workpiece (chips
  will be formed and a new surface will be
  exposed), set and lock the micrometer collar to
  0. Next, set the cross feed to 25 (which will
  remove 0.025 from the diameter) and then feed
  the tool to the stop.

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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Bring the feed back to just past the end of the
  shaft, adjust the cross feed to 50 and repeat the
  process until approximately 0.110 - 0.115 have
  been turned.
• Stop the lathe and measure the diameter using
  micrometers.
• Adjust the cross feed to make the final cut and
  proceed to turn the shaft to its final 0.386
  dimension.

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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Move the cutting tool away from the workpiece.
  Use the steel file to deburr the edges.

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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Turn off the lathe. Insert opposite end of
  workpiece into the chuck.
• Insert the center drill in the tailstock. Place
  tailstock near workpiece and lock into position.
  Turn on lathe and center drill a hole in the
  shaft.

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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Return the tail stock to its starting position.
  Remove the center drill and insert the 25 drill.
  Power on the lathe and proceed to drill a blind
  hole approximately 5/8 deep.

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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Stop the lathe, remove the drill and insert the
  tap guide into the chuck. Align the 10-32 tap
  with the hole and the insert the tip of the guide
  into the rear of the tap. Create a threaded hole
  by rotating the tap clockwise. For every full
  turn clockwise, rotate the tap about ½ to ¾ of a
  turn counterclockwise to remove any chip build-up.

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Lab Procedure Part B

• Procedure (refer to drawing in appendix B)
• Once a hole has been created, remove the shaft
  from the collet. Using the arbor press to
  assemble the shaft into the bracket.

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Summary Machining 1 Lab

• This lab preparation material introduced
• The basic principles of machining operations with
  focus on turning, drilling and related operations
  
• The objectives of and the expected outcomes from
  the evaluation of experimental trials
• Calculations required for this lab
• The experimental procedure and equipment used
• A number of pictures to familiarize the students
  with equipment, tools, and procedures related to
  this lab

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Appendix A Bracket
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Appendix B Shaft
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