Lesson La the Operations 3

8/2/2019 Lesson La the Operations 3

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Lesson Title: Lathe Operations

Lesson Duration: 4 hours

Industry Competencies: Participants will:

research and discuss theoretical and background information about engine lathesand turning operations

select cutting speeds and feeds, and calculate the RPM appropriate to a specific

material/cutting tool combination

link the basic theory of turning to tool geometry (chip formation)

describe the relative motions of the lathe and describe the interactions of various

subsystems, including the machine tool, machine controls, drive mechanisms,cutting tools, tool holder, work piece, and work holder

demonstrate safe operating procedures for each machine tool used (Comp. 2)

develop a list of lathe and turning operations, and identify the sequence ofoperations needed to make a specific product (Comp. 4)

use hand tools to support the setup and operation of lathe machinery (Comp. 5) operate lathes at an introductory level (Comp. 6)

select cutting speeds and feeds, and calculate the RPM appropriate to a specific

material/cutting tool combination (Comp. 7)

apply basic precision measurement instruments before, during, and after turning

operations to ensure that product specifications and tolerances are met (Comp. 9).

Specific Objectives: Participants will:

read schematics and engineering sketches accurately

measure accurately using SI and US systems and tools

employ all personal and environmental safety requirements collaborate successfully to solve machining problems

set up and use the lathe properly.

Assessment(s):

Rubric for Evaluating the Transfer Activity

Participant: Date:

Participant

Deliverable

Participant

Task with

Competency

Highly

CompetentCompetent

Needs

Improvement

Safe Operation ofmachinery

Operate machinetools in a safe and

proper manner.

Use hand tools to

support setup of

machinery.

(Comp. 1, 3, 4, 5)

Machinery andtools are operated

safely and in

accordance with

manufacturer's

instructions.

Safe and properoperating

procedures are not

followed.

Process Planning

Sheet: Making

Develop a list of

machining

Sketch of part is

detailed and

Sheet includes a

sketch of the part

Sheet is inaccurate

or incomplete.


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Parts for the

Robotic Gripper

operations and

identify the

sequence of

operations needed

to make the part.

(Comp. 2, 10)

professionally

presented. List of

operations shows

an indepth

understanding of

the process.

and complete list

of operations, in a

correct sequence

required to produce

the part.

Inspection Sheet:Making Parts for

the Robotic

Gripper

Record partmeasurements

before, during, and

after machining

and ensure thatspecifications have

been met. (Comp.

6, 9)

Examination ofpart tolerances on

inspection sheet

shows variation

from tolerancesspecified on

engineering

drawing.

Measurements ofpart to determine

conformance to

engineering

drawing areaccurately done

and recorded on

inspection sheet.

Sheet is inaccurateor incomplete.

Part Make a part within

tolerances.

(Comp. 4, 5, 7, 8)

Part is within

tolerances

specified on

engineering

drawing. Part

moves well with

parts made byother teams.

Part achieves the

correct basic

geometry of part as

specified on the

engineering

drawing.

Part is not

attempted, or is not

completed, or basic

geometry of part is

incorrect.

Overall Assessment Highly Competent CompetentNeeds

Improvement

Competency

or Task

Highly

Competent Competent

Needs

Improvement

Measurements areaccurate using both US

and SI devices.

All measurements aremade accurately with

full understanding and

ability to use

measurement tools.

All measurements aremade with appropriate

tool and are accurate.

One or moremeasurements are

incorrect and ability to

use appropriate tools is

not consistent.

Conversions within theUS system are accurate. All conversions areaccurate with full

understanding and

appropriate units

indicated.

All conversions areaccurate with

appropriate units

indicated.

One or more of theconversions is

inaccurate and units are

not displayed correctly.

Conversions with the SI

system are accurate.

All conversions are

accurate with full

understanding and

appropriate units

indicated.

All conversions are

accurate with

appropriate units

indicated.

One or more of the

conversions is

inaccurate and units are


Conversions between

the US and SI systemsare accurate.

All conversions are

accurate with fullunderstanding and

appropriate units

indicated.

All conversions are

accurate withappropriate units

indicated.

One or more of the

conversions isinaccurate and units are



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Competency

or Task

Highly

Competent Competent

Needs

Improvement

Write clearly and

effectively on a specific

topic.

Topic is fully addressed

with highly effective

supporting information

with no errors ingrammar, punctuation,

or spelling.


with adequate


and no errors ingrammar, punctuation,

or spelling.

Topic is not addressed

or poorly supported with

one or more errors in

grammar, spelling, andpunctuation.

Speak clearly and

present information

about a specific topic.


with highly effective


with a clear voice,

excellent syntax,

excellent grammar, and

superb volume.


with adequate


in a clear voice with

effective grammar and

pronunciation.

Topic is not addressed

or poorly attempted with

inadequate supporting

information, low voice,

and one or more errors

in grammar.

Production of a PartCompetency

or Task

Highly

Competent Competent

Needs

ImprovementMachine Operation

Analysis

All machine operations

were followed with high

level of quality and

superb detail.

All machine operations

were followed with high

level of quality.

One or more of the key

procedures were not

followed or poorly done.

Machine/Tool Use The actual machine and

related tool use wassuperb with no mistakes.

The actual machine and

related tool use wasdone well with required

detail.

There were one or more

instances of poor tooluse during the process.

Safety All safety rules were

followed exemplarywith assistance to

others.

All rules were followed

as directed.

One or more rules was

not followed whichestablished some risk.

Accuracy All parts were measuredand fabricated

accurately with exact

precision beyond any

tolerances.

All parts were measuredand fabricated

accurately within

acceptable tolerances.

One or more parts weremeasured wrong or

fabricated poorly outside

of required tolerances.

Resource(s):

Print Materials - Basic mathematics textbook and Machining textbook (to be identified)

Audiovisual -

Internet sites-Key word search - lathe, lathe operations, lathe safety, lathe manufacturers, lathe parts,

lathe attachments, lathe tooling.

Purpose of the Lesson:

To introduce participants to lathe machining operations, including safety, tooling, and

applications for manufacturing.


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Required Knowledge and Skills: Participants will:

perform basic operations in mathematics

measure accurately using SI and US tools and units

convert measurements between SI and US systems

read basic schematics and machine part drawings/sketches follow personal and environmental safety requirements.

Tools, Materials, Equipment Needed:

1 lathe

bar stock

1 pad of 3" x 5" Post-it Notes

1" x 6-1/2" bar stock

For the facing and center drilling portion of this activity, per participant:

setup tools

1 micrometer with collar

1 center drill reference chart in Machine Tool Practices

1 vernier caliper

same work piece used above

For the turning portion of this activity, per participant:

1 lathe

1 micrometer with collar

same work piece used above

Specific Safety Requirements:Everyone must wear safety glasses at all times during equipment demonstrations and

operator evaluations. Observe proper safety and operating procedures at all times. Dispose

of chips and other debris as required by your facility. Each participant must pass the Lathe

Safety Test and Operator Evaluation before being allowed to operate any lathe.Participants may not proceed until all safety knowledge is addressed. You must ensure that

participants can demonstrate safe and proper operating procedures before using equipment.

Lesson Elements: (5-E model)

Engagement:

In preparation for this activity, you should have assigned participants to research topicssuch as:

types of machine tools operations

types of tooling

ways of holding work

speeds

feed rates

tolerances


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surface finishes

measuring and measuring instruments.

At the beginning of this session, have the group decide how the discussion should proceed

(such as, work through a list or go around the room). Have them establish ground rules for

the discussion; for example, the person presenting information is allowed to finish beforethe rest of the group can ask questions or present differing opinions. Be sure to emphasize

the importance of respect for the ideas and information provided by others.

Review the parts of a lathe, either in this discussion or as part of the equipment

demonstration that follows.

Make sure that the discussion and/or demonstration includes the information that appears

on the quiz.

Exploration:

Before observing a lathe demonstration, participants should be required to visit one or morelathes available in the manufacturing laboratory and using a part identification worksheet

as shown below, they should identify and describe each machine part that has been labeledby the instructor with sticky notes or some other simple form of labeling.

Machine Part Number Machine Part Name Purpose or Description

Participants should view the following image and prepare a written description for lathe

machining operations. The written descriptions will be used to guide discussions led by theinstructor about what these machines can and cannot do.


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Another interesting exploration activity is to challenge participants to explore a variety ofLathe manufacturers and locate product descriptions and machine specifications for

comparison of machine capabilities and features. This research will help participants

understand the wide range or products and machine features depending on the scope ofproduction work needed by an organization. Participants can accomplish this asindependent or small team work. Examples are provided below to guide this research.


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YCL-1236/YCL-1340

Options: Taper Turning attachment Micro Carriage Stop

5-C Lever Collet Closer

2 axis Digital Readout

Birmingham YCL 12"dia x 36" Geared Head Bench Lathe Manufactured in China.

Floor stand included

7" diameter max swing over carriage 2 HP, 220 volt, 1 phase main motor

9 speeds from 70 - 1400 RPM

Standard Equipment:

6" 3-jaw chuck

8" 4-jaw chuck

10" face plate 1-1/2" spindle bore

3 3/4" steady rest

follow rest Gap

4-way tool post

thread chasing dial

2 dead centers reducing sleave

full splash guard chip tray

Automatic longitudinal and cross feeding

Hardened and ground Spindle and Bedways

12" swing x 36" center distance Precision Geared Head Gap Bench type including floorstand: $2,495.


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Birmingham CT-1440G Precision Lathe $3595.

Manufactured in Taiwan. ** Uses 110 volt electrics **

Swing over bed 14" [355mm] Between Centers 40" [1016mm]

D1-4 with 1-1/2" Spindle Bore [38mm]

Width of Bed 7-5/32"

Lathe bed is made of high tensile cast iron in rigid construction structure, the bed way ishardened and ground.

The main spindle is equipped with 2 precision taper roller bearings.

Provides 12 spindle speeds from 70 to 1350 RPM, quick speed change by lever. All gears head stock with oil immersed lubrication design, provides vibration free V-

belt replacement

2HP motor has power suitable for heavy duty cutting. Includes heavy duty floor stand

along with full length splash guard as standard equipment.

In addition to complete lathe turning centers, participants can locate and review

information about various components and lathe parts such as the examples shown below-


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Birmingham Extended Range Precision Gap Bed Lathes

Swing diameter over bed - chose from 26" / 32" / 40"

Between centers: 40" / 60" / 80" / 120" / 160" / 200" Width of bed 21 21/32"

20 HP main motor (15 HP ON DL-26 series only)

67 kinds of inch threads 18 speeds from 7.5 to 1000 RPM

D1-11 camlock with 5-1/8" spindle bore on most lathe sizes Main spindle hardened and precision ground

Bed made of fine grain high tensible cast iron 4-way rapid travers to carriage and cross slide

Bed ways induction hardened and precision ground

All gears and shafts hardened and precision ground Spindle supported at 3-point by precision bearings

Automatic lubrication system in headstock and feed box


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Hydra-control multi-disc clutch for spindle turning and brake

Manufactured in China

After discussing the lathe, participants are ready to observe a brief demonstration of the

machines capabilities. This demonstration should include a review of the parts of the

machine, proper nomenclature, and any specific safety procedures. One interestingapproach to the actual machine lathe demonstration and related setups is to have

participants complete the setups and then prepare photos of those key configurations which

could be used in participant tutorials or remedial instructional episodes needed throughoutthe course.


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A detailed machine parts drawing should be provided by instructor for participants toreview. This example provided below is very detailed and may not be needed for a

foundations course, but it is good for participants to review such documents to see thescope of detail in a basic turret lathe, including the motor and drive assemblies as well as

the lathe bed and various controls and attachments.

Participants should be able to review a lathe parts drawing or photo with parts labeled as

shown below. It is suggested that participants prepare their own documents by

photographing and then drawing detailed drawings to be kept in their class notebooks or

journals. These must be kept for future reference and exam studies.


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Explain and demonstrate the following turning operations and concepts, which the

participants will perform in the Lathe Exercise:

operating speeds and feeds

facing and center drilling turning to tight tolerance

Explanation:

Identify and describe the various types of machine tools:

engine lathes

gap beds

chuckers

turret lathes (old technology)

CNC lathes

automatic screw machines

Discuss (written and oral) the following operations:

turn

face

bore

thread

knurl

drill

ream

taper

grove trepan

internal vs. external operations

Discuss these types of tooling:

tool geometry of turning tool

tool geometry of facing tool

tool geometry of threading tool

tool geometry of boring bars

tool material type (HSS/carbides/ceramics)

Describe these ways of holding work:

chucks (3-jaw universal vs. 4-jaw independent)

face plate (collets)

between centers

Discuss how to determine proper RPM for lathe work: (RPM = (cutting speed x 4)

diameter)


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Extension:

Lead participants in a discussion of the activity by asking questions such as:

Is the lathe the most efficient way to produce this part?

What other operations can be performed on the lathe?

Is it easy to turn a part to a tight tolerance?

When turning to a tight tolerance, what went wrong or was unexpected? How did

you correct the problems you encountered?

What are the economies of tight tolerances ( .001")?

How can you match your machining speeds and techniques, as well as your

measuring instruments, to the tolerances specified on the print?

1. Perform the following practice operations on the lathe:

Using pre-made Post-it Notes, label the parts of the lathe. Remove the Post-it Notes.

Practice changing speeds on the lathe. Practice operating automatic cross and longitudinal feeds.

2. Perform the following facing and center drilling operations on the lathe:

Load a tool and set it to center.

Select the proper center drill using the reference chart in Machine Tool Practices.

Face and center drill both ends of the work piece.

Use a caliper to measure the length of the work piece:

___________________________

Explain how the choice of measuring tools corresponds to blueprint tolerances and

whether a caliper is accurately calibrated.

3. Perform the following operations pertaining to turning to tight tolerance:

Set up the work piece between chuck and center.

Determine whether the lathe is equipped with a single- or double-depth micrometer.

Using Engineering Drawing: Lathe Exercise for reference, practice turning

diameters to size.

Discuss how to turn a diameter to a tolerance of .001".

Discuss how surface finish affects tight tolerance.

Use a micrometer to measure the diameters of the work piece.

Consider the micrometers tolerances, measuring range, usage, and calibration to

discuss why a part may be within tolerances though the micrometer may indicateotherwise:

The following planning sheet can be used to guide the practice exercises identified above.


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Process Planning Sheet: Lathe Exercise

Participant: Date:

Sketch of Part

Operations Materials & Equipment

Approved By:

The following is a part drawing for a thread cutting exercise that can be presented toparticipants as part of basic lathe skill development and refinement. The instructor can

offer other similar examples for participants to complete based on their class ability level.


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The following images are provided for the instructor to help guide participants in their

understanding of thread cutting operations-

Three Wire Method of measuring threads:


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Thread Nomenclature


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Screw Thread Lead and Pitch


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Enrichment:

Have participants investigate the history of lathe machines and prepare a timeline that

begins with crude devices such as the one shown below. Key machine features andinnovations should be highlighted in their timelines. This activity can be accomplished as

independent or collaborative work.


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Evaluation:

1. List two ways to face off a piece to a given dimension.Turn the compound 30 and feed in twice the amount that you want to cut. Turn the

compound 90 and feed in the same amount that you want to cut.

2. What is backlash and what adjustments do you have to make for backlash?

Backlash is play in the longitudinal or cross feed screw. In the backlash area, the

micrometer dial will change but the corresponding machine slide will not move. Aslong as you have removed the backlash and are moving the screw in the same direction,

you do not need to worry about backlash. To get rid of backlash when you change

directions, go two full turns past your position and then come back to your position.

3. Calculate the correct spindle speed for turning 2-1/2" diameter cold-rolled steel.

Use the formula:

cutting speed x 4 diameter of work piece

100 x 4 (2.5in.)160 RPM

4. What happens if you drill too deeply with a center drill?

If you drill too deeply, the bearing surface for the center will be a sharp edge instead of

a 60 angle. This will give a poor bearing surface.

5. You need to turn a work piece to a 0.547 0.002 diameter and you're turned down to

0.557. What are the last five steps you will take to hit the final size correctly?

a. Turn the micrometer collar to the desired cut.b. Start the cut for 1/8-1/4 inch.

c. Quickly move the cutter to the right of the work piece without changing the

micrometer collar.d. Measure whether you are cutting the desired diameter.

e. If so, continue the cut. If not, readjust the micrometer collar.

6. What is the difference between single-depth and double-depth cross feed

micrometer collars?

A single-depth micrometer collar cuts twice as deep as the reading on the micrometer

collar. A double-depth micrometer collar cuts the same amount as the reading on themicrometer collar.

7. Why do you need to center drill a work piece?To provide a bearing surface for a center or to provide a starting point for a drill since a

drill tends to walk when it starts the cut.

8. You have a 0.002 tolerance on your blueprint, but when you made the final cut, the

surface finish was very rough. Is this a problem? Why or why not?

Yes. If the surface finish is rough, the high points of the surface irregularities will wear

off quickly, changing the size of the work piece.


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9. What precaution should you take when turning between a chuck and a center? Explain.

The work piece can slip into the chuck jaws and move away from the tailstock center,leaving it unsupported at the tailstock end. This unsupported end can whip around,

causing a hazard for the lathe operator. Also, the chuck jaws may not align the work

piece with the tailstock center.

10. What is a good feed rate for a roughing cut on the lathe? Explain. The feed rate for

roughing should be 1/5 to 1/10 of the depth of cut.

11. What is a good feed rate for a finishing cut on the lathe? Explain. Finishing feeds

should be .003 to .005 for steel.


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The following inspection sheet can be used to evaluate all Lathe exercises.

Inspection Sheet: Lathe Exercise

Participant: Date:

Description Required Sizes Machined Sizes

Acceptable

Within

Tolerance

Yes No


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Enrichment:

1. Look up recommended feed rates from technical manuals for tool suppliers.

2. Discuss the quick-change gear box.3. Use two or three different feed rates to explain how feed rate affects surface finish.

4. Discuss the typical tolerances for various lathe operations and tooling.

5. Describe the typical finishes generated on lathes.6. Discuss the use of graduated dials, compound rest stops, digital readouts, and gauges.

Lesson La the Operations 3

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Transcript of Lesson La the Operations 3