CBLM_Interpreting Technical Drawing

JZGMSAT TESDA IV

Prepare/Interpret Technical Drawing

Version No.: 2 Date: August 10, 2009 By: Glenn F. Salandanan Page 1 of 18

INTERPRETING TECHNICAL DRAWING

This is the first of the modular series produced by the Jacobo Z. Gonzales Memorial School of Arts and Trades –

Technical Education and Skills Development Authority Region IV-A

ACHIEVING COMPETENCE IN

PREPARING/INTERPRETING TECHNICAL DRAWING

JZGMSAT TESDA IV



TABLE OF CONTENTS Content Page Number

I. LEARNING GUIDE OVERVIEW ........................................................................ 3

II. HOW TO USE THIS GUIDE ............................................................................... 4

III. LEARNING ACTIVITIES ..................................................................................... 5

IV. INFORMATION SHEET 1: ALPHABET OF LINES ............................................. 6

INFORMATION SHEET 2: ORTHOGRAPHIC PROJECTION

A. ORTHOGRAPHIC PROJECTION ................................................................ 9

B. STEPS IN SELECTING CORRECT VIEWS OF AN OBJECT ...................... 9

C. PRINCIPAL DIMENSIONS OF AN OBJECT .............................................. 10

D. STEPS IN PROJECTING THE THREE MAIN VIEWS OF AN OBJECT .... 11

V. SELF CHECK 1 .................................................................................................. 8

SELF-CHECK 2 ................................................................................................ 13

VI. ACTIVITY SHEET NO. 1: SKETCHING THREE MAIN VIEWS OF

AN OBJECT ..................................................................................................... 14

VII. ANSWER KEYS ......................................................................................... 16-17

VIII. RECORD OF COMPETENCE .......................................................................... 18

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LEARNING GUIDE OVERVIEW

In the broad field of technical drawings, various projection methods are used to represent objects. Each method has its own advantages and disadvantages.

The normal technical drawing is shown in orthogonal projection, in which more than one view is used to draw and completely define an object.

However, to be able to represent the different views of an object one must be acquainted with the different forms of lines. The various lines used in drawing form the alphabet of the drafting language.

In this learning material, the students should be able to apply the alphabet of lines in projecting the principal views of an object.

Competencies will be demonstrated by completing the job sheet and the unit test with a minimum score of 75 percent.

OBJECTIVES When you have successfully completed the learning activities in this

material, you will be able to: 1. Identify the different alphabet of lines; 2. Steps in selecting correct views of an object; 3. Identify the dimensions of an object; and 4. Project the three main views of an object.

CONTENTS This learning material includes the following:

1. Alphabet of lines 2. Orthographic Projection 3. Steps in Selecting Correct Views of an Object 4. Principal Dimensions of an Object 5. Steps in Projecting the Three Main Views

PRE-REQUISITES The completion of this learning material requires you to have a basic

understanding of: If you are unfamiliar with any of the above concepts, work on________ before working on this learning guide.

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HOW TO USE THIS LEARNING GUIDE This Learning Guide will lead you through a series of activities which will require you to work at your own pace. These activities will ask you to complete associated learning and practice activities in order to gain the knowledge and skills you need to achieve the learning objectives stated earlier. Refer to Learning Activity Page to know the sequence of learning tasks to undergo and the appropriate resources to use in each task. This page will serve as your road map towards the achievement of objectives. Read the information sheets. This will give you an understanding of the work, and why things are done the way they are. Complete the activities as directed in the activity/practice sheets. These will test your knowledge and give you practice of doing the tasks involved. Performance criteria for assessing practical exercise are shown to guide you in undertaking the practical exercises. Always be aware of safety requirements highlighted in this material. Ask for clearance in using some tools and equipment. Should you require some assistance and clarification, consult your trainer or facilitator. They should be available anytime you need them. Answer self-checks found in each section of the learning guide. Do not write anything on this learning guide; provide separate sheets for your answers. Self-checks will let you know how you are going. To know how you fared with self checks, review the answer keys found at the end of the learning guide. When you had completed all the tasks required in this learning guide, an assessment exercise will be given to evaluate if you are already competent with the specified learning outcomes in and ready for the next task. .If you feel ready for the assessment, consult the facilitator. A record of competency is provided on the last page to reflect how much of the required assessment criteria have been met. You may already have some or most of the knowledge and skills covered in this learner’s guide. Talk to your trainer about having them formally recognized. If you have qualification or certificate of competence from previous training, show it to your trainer. If the skills you acquired are still current and relevant to the unit of competency they may become part of the evidence you can present for Recognition of Prior Learning (RPL). If you are not sure about the accuracy of your skills, discuss it with your trainer. glen

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LEARNING ACTIVITIES

In order to accomplish the objectives stated in this leaning guide, you must perform the learning steps below. Beside each step are the resources or special instructions you will use to accomplish the corresponding activity.

LEARNING STEPS RESOURCES/SPECIFIC INSTRUCTIONS

1. Student will ask the instructor of the

materials to be used

2. Read: Information Sheet No. 1

3. Answer: Self Check 1

4. Read: Information Sheet No. 2

5. Answer: Self Check 2

6. Perform: Activity Sheet No. 1

1. Instructor will provide the learning

materials in Interpreting Technical

Drawing

2. Information Sheet No 1: Alphabet of

Lines

3. Self Check No. 1: Alphabet of Lines

4. Information Sheet No. 2:

Orthographic Projection

5. Self Check 2: Orthographic

Projection

6. Activity Sheet No. 1: Sketching three

Main Views of an Object

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INFORMATION SHEET NO: 1

ALPHABET OF LINES I. Basic Types of Lines and their Uses

a. Visible lines – Used to show visible edges or contours of an object (NOTE: Visible lines are sometimes called object lines.)

b. Hidden lines – Used to show surfaces or

features on an object that are not visible c. Center lines – Used to show the centers

of holes, round shapes, or the travel of a center (path or motion)

d. Section lines – Used to show a surface

that has been cut in a section view e. Extension lines – Used for placing

dimensions; these extend (but do not touch) from the lengths and widths of objects

f. Dimension lines – Used to show the size

(dimensions) of an object; spans from one extension line to the next, has arrowhead at both ends, and is broken in the middle fro the measurement number (dimension)

g. Leader lines – Used to direct descriptive

information, notes, or special dimensions to features on the drawing

h. Cutting-plane lines – Used to show where

a section has been taken; arrows on the end show the direction in which the section was taken

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i. Break lines – Used to show that part of

the object has been removed or broken away 1. Short breaks are for freehand, jagged

lines 2. Long breaks are solid with a Z symbol

inserted in several places j. Phantom lines – Used to show the

position of an object that moves (rotated position)

k. Border lines – Used to define the outer

edges or margins on the drafting media; the drawing and all other information is inside this border.

Figure 1. Application of alphabet of lines.

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SELF- CHECK NO. 1 Check your mastery in Alphabet of lines by completing the tasks below.

1. Identify the alphabet of lines by writing your answer on the space provided.

A B A B

A B

B A

2. Sketch circles with a diameter of:

a. 25mm b. 50mm c. 30mm

1. ______________

2. ______________

3. ______________

4. ______________

5. ______________ glennfsa

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INFORMATION SHEET NO: 2

ORTHOGRAPHIC PROJECTION

A. Orthographic Projection

An orthographic projection is a representation of separate views of an object on a two-dimensional surface. It reveals the width, depth and height of the object.

Ortho means “straight or at right angle” and graphic means “written or drawn”. Projection comes from two Latin words: “pro,” meaning “forward,” and “jacere,” meaning “to throw.” The projection is achieved by viewing the object from a point assumed to be at infinity

(an indefinitely great distance away). The line of sight or projectors are parallel to each other and perpendicular to the plane of projection.

Figure 1. Visualizing one view of an orthographic projection B. Steps in Selecting Correct Views of an Object

1. Select the number of views necessary to represent the object. This may require only one

view or as many as all six views. Only draw as many views as are necessary. 2. Select the front view which:

a. Best describes contour shape. b. Contains the least number of hidden lines. c. Is usually the longest view. d. Shows object in normal position.

Figure 2. Objects with very little thickness require only one view

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Figure 3. Two-view drawing

3. Select alternate position for right side view if drawing area is crowded.

Figure 4. Normal location Figure 5. Alternate location

4. Select view positions to avoid crowding of dimensions and notes.

C. Principal Dimensions of an Object

Figure 6. Principal dimensions of an object

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Width. This is a perpendicular distance between two profile planes.

Height. This the perpendicular distance between two horizontal planes

Depth. This is the perpendicular distance between two frontal planes.

D. Steps in Projecting the Three Main Views of an Object 1. Study the given object

2. Determine the number of views

3. Locate the views

4. Block in the views with light, thin lines

5. Lay off the principal measurements

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6. Draw the principal lines

7. Lay off the measurements for the details

( center for arcs, circles, and triangular

ribs)

8. Draw the circles and arcs

9. Draw any additional lines needed to

complete the views

10. Darken the lines where necessary to

make them sharp and black and of the

proper thickness

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SELF- CHECK NO. 2 Check your mastery in orthographic projection by completing the tasks below. I. MULTIPLE CHOICE. Write only the letter that corresponds to your answer.

1. Method of representing separate views of an object on a two-dimensional surface

a. orthographic projection b. orthographic drawing c. isometric drawing d. perspective

2. Found below top view which show s the shape, width and depth of the object. a. top view b. front view c. bottom view d. rear view

3. Found at the back of the front view. a. rear view b. side view c. frontal plane d. none of the above

4. The perpendicular distance between two profile plane a. length b. width c. depth d. height

5. The perpendicular distance between two horizontal plane a. height b. depth c. width d. length

6. The word orthographic comes from the two Greek words ortho and graphos meaning a. forward b. straight/at right angle c. to write/to draw d. both b & c

7. The perpendicular distance between two frontal plane a. width b. length c. depth d. height

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ACTIVITY SHEET NO. 1

Sketching Three Main Views of an Object

A. Objectives:

After completing the activity you should be able to:

1. Identify the three main views of the given object; and,

2. Draw the necessary orthographic views of the given object to show its exact shape.

B. Materials:

A4 size drawing paper Eraser

C. Tools:

Drawing pencil T-square Triangles (30ºx60º, 45ºx45º) Erasing shield

D. Procedure:

Study the example below and then complete the

assigned problem.

Example:

1. Sketch the horizontal lines to locate the height of the object. (NOTE: The distance at the top and bottom of the paper should be the same. The distance between the top and front views can be the same as the top and bottom or slightly less than that space.)

2. Sketch the vertical lines to locate the width and depth of the object. (NOTE: The distance at the left side and the right side of the paper should be the same. The distance between the views can be the same as that on the left side and right side or slightly less than that space. In the top and side)

3. Block in details using diagonals to locate centers, if necessary, and lightly construct the circles and arcs.

4. Add line features to the views of the object.

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5. Use eraser to lighten construction lines and darken in visible lines

Problem: Layouts for Orthographic drawing problem will be explained by the instructor. Sketch the

three main views of the given isometric drawing below using the grid provided for measurement.

on an A4 size drawing sheet. Do not erase light construction lines.

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ANSWER KEY NO. 1

Check your answer with the answer key below. If you fail to get it right, refer back to corresponding resources until you make it perfect.

1. Center line

2. Hidden line

3. Cutting-plane line

4. Object line

5. Section line

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ANSWER KEY NO. 2

Check your answer with the answer key below. If you fail to get it right, refer back to corresponding resources until you make it perfect.

1. A

2. C

3. A

4. B

5. A

6. 7

7. C

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RECORD OF COMPETENCE Below are your assessment ratings:

ASSESSMENT /PERFORMANCE CRITERIA

YES NO

1. Components, assemblies or objects recognized as required

2. Dimensions of the key features of the objects depicted in the drawing correctly identified

3. Symbols used in the drawing identified and interpreted correctly

4. Drawing checked and validated against job requirements or equipment in accordance with standard operating procedures

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Documents

CBLM_Interpreting Technical Drawing