Machining 1 Lab Presentation

8/3/2019 Machining 1 Lab Presentation

http://slidepdf.com/reader/full/machining-1-lab-presentation 1/64

ISE 311

Machining I Lab

in conjunction with

Chapters 21, 22, and 23 in the text book

³Fundamentals of Modern Manufacturing´

Third EditionMikell P. Groover

April 17 th , 2008



2

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



3

Introduction

Basic Principles of Machining

Machining is a manufacturing process in which a cutting tool isused 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 ³chips.´

As chips fall off the workpiece a new surface is exposed.

A schematic showing a

simple machining process



4

Introduction


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 16in (0.4 m) can be produced by

machining processes.



5

Introduction


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 . The rake angle 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.



6

Machining I


The three most common types of conventionalmachining processes are:

± Drilling

± Turning

± Milling

Other conventional machining processes include:

± Shaping

± Planing ± Broaching

± Sawing

± Grinding



7

Machining I

Drilling

Drilling is used to create round holes in workpieces using arotating 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

(a) (b)

Figure depicting

(a) through holes and

(b) blind holes



The figure below depicts a twist drill ± the mostcommonly used drill bit.

8

Twist drill bit



9

Machining I

Drilling

The body of a twist drill has two spiral f lutes whichusually 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 oppositedirections).

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°.





11

Machining I

Drilling

Drills are limited to a depth of no greater than4

times itsdiameter because of the high temperature and the highload 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 thestraightness and dimensional accuracy of the hole



Machining I

Drilling

To solve the temperature rise problem, the following iscommon:

Peck drilling: the drill is periodically withdrawn from the

hole to clear chips

Some drills have internal holes in the drill body throughwhich 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).

12



13

Machining I

Drilling

Prior to drilling, centering (or center drilling) is used tocreate a starter hole (using a center drill). This is used

to:

Define the location of the hole. Solve the ³Walking´ or ³Wandering´ problem which

happens because of drill deflection before the chisel

penetrates the workpiece.



14

Machining I

Drilling

The following operations are all related to drilling andcan 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 andimprove 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.



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.

15



16

Machining I

Drilling

The figure below illustrates the various operationsrelated to drilling.

(a) Reaming(b) Tapping

(c) Counterboring

(d) Countersinking

(e) Center drilling

(f) Spot facing



17

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



18

Machining I

Turning and Facing

Turning is a machining process performed on a lathe inwhich 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.



19

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.



20

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



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

21



22

Machining I

Turning and Facing

(a) Facing

(b) Taper turning

(c) Contour turning

(d) Form turning

(e) Chamfering

(f) Cutoff

(g) Threading

(h) Boring(i) Drilling

(j) Knurling

The figure below displays operations related to turning

(a) (d)(c)(b)

(g)(f)(e)

(h) (i) (j)



23

Machining I

The Lathe

The engine lathe is a manually operated machine toolwhich is widely used in low to medium production.

Initially, these machine tools were powered by steam

engines, hence the term ³engine´ 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 rotatesthe workpiece. The tailstock is

occasionally used to support one

end of the workpiece.



24

Machining I

The Lathe

The cutting tool is held in the tool post . The tool post ismounted 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 operationcan be carried out.



25

Machining I

The Lathe

The size of a lathe is determined by its swing andmaximum 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 theaxis 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.



26

Machining I

The Lathe

There are4

common methods to hold the workpiece in alathe as shown in the figure below: (a) mounting

between centers, (b) chuck, (c) collet, and (d) face plate.



27

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 withrelatively small diameters.

The chuck (shown to the right)

utilizes either three or four jawsto 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.



28

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.



29

Machining I

The Lathe

A face plate is mounted onto the spindle and is used to holdworkpieces with non-cylindrical shapes. The face plate is

equipped with custom designed clamps which are manufactured

specifically to a particular application.



Machining I

Cutting Parameter in turning

30

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



Machining I

Required 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 R MR (in3/min) is the

volume of material removed (in3) divided by time

(min)31

D

v N

T

12!



Machining I

Required Calculations for this lab

Machining power, P, is the energy per unit timerequired to perform a machining operation (usually in

Horse Power, HP)

1 HP = 33, 000 lb*ft/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:

32

MRU R P P v!



Machining I

Tool 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.33



34

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 inmachining

Learn to calculate cutting speed, material removal rate, and

spindle horsepower



35

Lab Safety

Everyone MUST wear approved safety glasses

Remove or secure anything which might become caught inrotating 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 hangsmore 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.



36

Lab Procedure ± Part A

You will need to use the drill press and performdrilling 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



37


Head

Forward/Reverse lever

Column

Speed adjustment

Chuck

Spindle

Table



38


23/64´ Drill 0.375´ Reamer

7/32´ DrillCenter Drill

Countersink toolCounterbore tool



39


Procedure: ( re f er to t he drawing in appendix A)1. 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.



40


Procedure: ( re f er to drawing in appendix A)

2. Once the center lines for the 3

holes have been marked,clamp the workpiece in theholder on the drill press.

3. Locate the center drill in the

chuck and, without turning thedrill press on, manually alignthe center drill to one of thecross hairs that are inscribedon 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!



41



4. 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.

5. Hold the workpiece in place with your left hand and withyour right hand bring the center drill down to the surface of

the workpiece.

6. Slowly create a starter hole. Once a hole has been created

return the drill press to its starting position and turn themachine off.

7. Repeat step 3 for the remaining 2 holes. The speed will

remain the same. Apply lubricant, if necessary.



42




43


Procedure: ( re f er to drawing in

appendix A)

8. Remove the center drillonce all three starter holeshave been created andreplace it with the 23/64´

drill.9. With the drill press off,

manually align the drill bitwith the middle hole.

10. Turn the machine toFORWARD, adjust thespeed accordingly, andapply the lubricant asnecessary. Drill a throughhole and return the drill

press to its home position.



44



11. Remove the 23/64´ drill bit from the chuck and insert the

3/8´ reamer.

12. 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 tomanually align the cutting tool in this step.



45



13. 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.

14. 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.

15. Repeat step #15 for the third and final hole.



46


Procedure:( re f er to drawing in appendix A)

16. Remove the 7/32´ drill and place the counterbore tool intothe chuck.

17. Manually align the counterbore tool with one of the outsideholes. Turn on the drill press, adjust the speed, apply thelubricant, and drill a blind hole approximately 3/8´ deep.



47



18. Turn off the drill press. Remove the counterbore tool andinsert the countersink tool into the chuck.

19. Manually align the countersink tool with the third hole. Turnon the drill press, apply the lubricant, and drill a countersink hole.



48



20. If time permits, deburr the bottom face of the bracket usingthe countersink tool. Align the countersink tool with each of the three holes that have been drilled and remove onlyenough material to remove the burrs created by drilling.



49

Lab Procedure ± Part B

You will need to use the engine lathe to performfacing, 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



50


Chuck Headstock

Spindle speed

selector

Feed selector

Ways

Lead screw

Bed

Tool post

Cross slide

Tailstock

Feed handwheel

On/Off levers

Cross feed

handwheel



51


Turning tool

Facing tool

Tap

Tap guide

Tap holder



52


Procedure:( re f er to drawing in appendix B)

1. Insert and secure the workpiece into the collet (or chuck).

2. Turn on the lathe by lifting on the lever.

3. Rotate the wheel that controls the feed counterclockwise and

place the tool in line with the workpiece.4. 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.

5. 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



53




54



6. Remove the facing tool and insert the turning tool. Adjust the

feed stop to 3/8´ from the initial position.



55


Procedure:( re f er to drawing in

appendix B)

7. Turn on the lathe and cross

feed the tool. Once the tool

slightly touches the

workpiece (chips will beformed 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.



56


Procedure: ( re f er to drawing in

appendix B)

8. 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 beenturned.

9. Stop the lathe and measure the

diameter using micrometers.

10.Adjust the cross feed to make

the final cut and proceed toturn the shaft to its final

0.386´ dimension.



57



11. Move the cutting tool away from the workpiece. Use the steel

file to deburr the edges.



58



12. Turn off the lathe. Insert opposite end of workpiece into the

chuck.

13. 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.



59



14. 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.



60



15. 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.



61


Procedure: ( re f er to drawing in appendix B)

16. Once a hole has been created, remove the shaft from the

collet. Using the arbor press to assemble the shaft into the

bracket.



62

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 theevaluation of experimental trials

Calculations required for this lab

The experimental procedure and equipment used

A number of pictures to familiarize the students withequipment, tools, and procedures related to this lab



63

Appendix A ± Bracket

Operation Description Tool RPM Oil

1 Mark hole locations Scribe and 6´ scale N/A No2 Center drill (3) hole Center Drill 900 No

3 Drill thru center hole 23/64´ Drill 325 Yes

4 Ream center hole 0.375´ Reamer 220 Yes

5 Drill thru (2) outside holes 7/32´ Drill 650 Yes

6 Counterbore (1) outside hole #10 Counterbore 220 Yes

7 Countersink (1) outside hole #10 Countersink 220 Yes

8 Deburr reverse side #10 Countersink 220 No



64

Appendix B ± Shaft

Operation Description Tool RPM Oil

1 Face until perpendicular Facing Tool 900 No

2 Turn 0.376´ x 3/8´ Turning Tool 900 No3 Face until perpendicular Facing Tool 900 No

4 Center drill Center Drill 900 No

5 Drill 5/8´ deep #25 Drill 900 No

6 Tap #10-32 x 1.2 deep #10-32 Tap N/A Yes

Date post:	06-Apr-2018
Category:	Documents
Upload:	santhosh-kumar
View:	220 times
Download:	0 times

Machining 1 Lab Presentation

Documents