CBLM_Isometric Drawing

Version No.: 1 Date: May 12, 2006

By: Glenn F. Salandanan

JZGMSAT TESDA IV

Performing Drawing Fundamentals

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ISOMETRIC 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



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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

A. ISOMETRIC DRAWING THEORY ……………………………….……. 6

B. NON-ISOMETRIC LINES ………………………………………………. 7

C. ANGLES IN ISOMETRIC ………………………………………………. 8

D. CIRCLES IN ISOMETRIC………………………………………………..9

V. SELF CHECK ………………………………………………………………... 11

VI. ASSIGNMENT SHEET: ISOMETRIC CIRCLES ………………………… 12

VII. JOB SHEET

1. ISOMETRIC DRAWING ………………………………….……13

VIII. ANSWER KEY ………………………………………………………………. 15

IX. RECORD OF COMPETENCE …………………………………….………. 16



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LEARNING GUIDE OVERVIEW

Isometric drawing is a popular method used to prepare pictorial views. It is usually

preferred to oblique method since it reduces much of the distortion that oblique drawing

produces.

This learning material includes definition of terms in isometric drawing and isometric

drawing theory will also be discussed. Difference between isometric and non-isometric lines are

also included. To measure the level of learning, students will layout object parts in isometric.

OBJECTIVES When you have successfully completed the learning activities in this

material, you will be able to: 1. Define isometric drawing; 2. Discuss isometric drawing theory; 3. Identify isometric and non-isometric lines; 4. Sketch and draw isometric drawing; and, 5. Make circles and arcs in isometric.

CONTENTS This learning material includes the following: 1. Isometric Drawing Theory 2. Non-Isometric Lines 3. Angles in Isometric 4. Circles in Isometric

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.



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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

4. Perform: Assignment Sheet No. 1

5. Perform: Job Sheet No. 1

1. Instructor will provide the learning

materials in First-Angle Projection

2. Information sheet No 1: Isometric

Drawing

3. Self Check: Isometric Drawing

4. Assignment Sheet No. 1:

Isometric Circles

5. The instructor will further explain

how to make isometric circles in

all planes of projection

6. Job Sheet No. 1: Isometric

Drawing



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INFORMATION SHEET NO: 1

ISOMETRIC DRAWING

A. ISOMETRIC DRAWING THEORY

Isometric drawing represents three dimensions on a two dimensional surface (your drawing). These dimensions are: X – Height; Y – Width; and Z – Depth.

In order to master Isometric drawing, you will need to remember these four fundamental

principles: 1. All lines on the same axis remain parallel and do not

meet. 2. All lines are based on a 120° grid.

3. There’s no diminution (things do not get smaller in the

distance).

4. There’s no horizon line on the page – you are either looking from a diagonal angle up or down.

FIG. 1. ISOMETRIC AXES

FIG. 2. ISOMETRIC BOXES

FIG. 3. LINES ON THE SAME AXIS REMAIN

PARALLEL

Figure 2 shows these two isometric boxes, all lines are parallel and all corners of the

objects have 120° angle.



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FIG. 4. USE OF 30° X 60° TRIANGLE IN CONSTRUCTING ISOMETRIC OBJECT.

FIG. 5. USING THE 120° ISOMETRIC GRID

A 30°X60°X90° triangle is a useful tool to help you construct an isometric drawing. Also,

Isometric grids can be used to assist you in this view.

B. NON-ISOMETRIC LINES If you examine the isometric drawing shown below, you will note that each line in the

drawing is parallel to one or another of the legs of the isometric axis. You will also notice that each line is a normal line in the multi-view projection. Recall that a normal line is a line that, in a normal multi-view projection, is parallel to two of the planes of projection and perpendicular to the third.

FIG. 6. ISOMETRIC LINES PARALLEL TO THE THREE ISOMETRIC AXES



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FIG. 7. A NON-ISOMETRIC LINE (AB) IN AN ISOMETRIC DRAWING.

NON-ISOMETRIC LINE is a line that is not parallel to any one of the three legs of the isometric axis. It is not a normal line in a normal multi-view projection of the object.

The part of Figure 7 shows a two-

view normal multi-view projection of a block. Though the line AB is parallel to the horizontal plane of projection, it is oblique to both the vertical and the profile planes. It is therefore not a normal, but an oblique line in the multi-view projection, and it will be a non-isometric line in an isometric projection or drawing of the same object.

C. ANGLES IN ISOMETRIC

In a normal multiview drawing of an object, an angle will appear in its true size. In an isometric drawing, an angle never appears in its true size. Even an angle formed by normal lines, such as each of the

90° corner angles of the block shown in the bottom part of Figure 8, appears distorted in isometric.

The same principle used in transferring a non-isometric line is used to transfer an angle in isometric. The upper part of Figure 8 shows a two-view orthographic projection of a block. On the top face of the block, the line AB makes a

40° angle with the front edge. The line AB is an oblique (that is, not normal) line, which will appear as a non-isometric line in the isometric drawing. You locate the end points of AB on the isometric drawing by measuring distances along normal lines on the multi-view projection and laying them off along the corresponding isometric lines on the isometric drawing. The angle that

measures 40° on the top multi-view drawing

measures only about 32° on the isometric drawing. Note, however, that it is labeled

40° on the isometric drawing. This is



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because it actually is a 40° angle, as it would look on a surface plane at the isometric angle of inclination.

FIG. 8. DRAWING AN ANGLE IN ISOMETRIC.

D. CIRCLES IN ISOMETRIC

A circle in a normal multiview projection will appear as an ellipse in an isometric drawing. This is shown in Figure 9, view A. The procedure that maybe used to construct an isometric circle is shown in Figure 9, view B.

1. Draw the isometric center lines of the circle. Then, using those center lines, lay off an isometric square with sides equal to the diameter of the circle.

FIG. 9. (A) CIRCLE ON A NORMAL MULTIVIEW APPEARS AS AN ELLIPSE IN AN ISOMETRIC DRAWING.

(B) FOUR-POINT METHOD IS USED IN MAKING AN ISOMETRIC CIRCLE.

2. From the near corners of the box, draw bisectors to the opposite intersections of the centerlines and the box. The bisectors will intersect at four points (A, A´, B, B´), which will be the centers of four arcs.

3. Draw two large arcs with radius R, using Points A and A´ as centers, Draw the two smaller arcs with radius r, using Points B and B´ as centers.



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SELF- CHECK NO. 1

Check your mastery in Isometric Drawing by completing the tasks below.

MATCHING TYPE. Match pictorial drawings A to M with Orthographic drawings. Simply write the letter of your choice below the corresponding numbers.



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ASSIGNMENT SHEET NO. 1

Isometric Circle A. Objectives:

After completing the activity you should be able to: 1. Draw isometric circle based from a given diameter; 2. Draw isometric circle in three planes of projection; and, 3. Produce properly drawn isometric circle.

B. Tool and Materials: A4 size drawing paper T-square Eraser Triangles (30ºx60º, 45ºx45º)

Drawing pencil Masking tape

C. Procedure

CIRCLES IN ISOMETRIC 1. Draw the isometric center lines of the circle. Then, using those center lines, lay off an

isometric square with sides equal to the diameter of the circle.

(A) CIRCLE ON A NORMAL MULTIVIEW APPEARS AS AN ELLIPSE IN AN ISOMETRIC DRAWING. (B) FOUR-POINT METHOD IS USED IN MAKING AN ISOMETRIC CIRCLE.

4. From the near corners of the box, draw bisectors to the opposite intersections of the

center lines and the box. The bisectors will intersect at four points (A, A´, B, B´), which will be the centers of four arcs.

5. Draw two large arcs with radius R, using Points A and A´ as centers, Draw the two smaller arcs with radius r, using Points B and B´ as centers.

PROBLEM: 1. Draw an isometric circles in all of the three planes of projection. A given diameter of 50mm is required.

Note: Size of the construction (crate) lines should be 50mm in all axes.



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JOB SHEET NO. 1

Isometric Drawing A. Objectives:

After completing the activity you should be able to: a. Show the three main views of the given isometric drawing in first-angle

projection; b. Draw symbol for first-angle projection; and, c. Produce properly drawn orthographic drawing in first-angle projection.

B. Tool and Materials: A4 size drawing paper T-square Eraser Triangles (30ºx60º, 45ºx45º)

Drawing pencil Masking tape

C. Procedure

STEPS IN ISOMETRIC DRAWING

1. Choose the orientation. Make sure the front view is along the left side of the isometric

drawing. The length of the object should be projected back at 330°. 2. Sketch the overall block that will represent the isometric drawing. Do your best to align

the drawing in the middle of the sheet. (do not allow portions of the drawing to be cut off)

SEVERAL STEPS IN MAKING ISOMETRIC DRAWING

3. Add construction line details (you may make mistakes). Details consist of circles, arcs, holes, angled lines, or any other lines that represent unique features in the object. (details should be sketched using 4H lead)

4. Darken visible lines. Using your 2H lead (for finished drawings) darken the edges of your object to make them stand out to the viewer.



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DRAWING PROBLEM

The isometric drawing should be made using A4 drawing sheet as assigned. On drawings to be executed with instruments, show all construction lines required in the solution.

PROBLEM 1. Draw the isometric drawing of the given multiview. Refer the measurements above. Omit dimension



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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. E

2. H

3. M

4. K

5. C

6. D

7. G

8. J

9. L

10. A

11. B

12. F



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RECORD OF COMPETENCE Below are your assessment ratings:

ASSESSMENT /PERFORMANCE

CRITERIA YES NO

1. Know isometric drawing theory

2. Isometric drawing from the given orthographic projection are properly drawn using necessary drawing instruments

CBLM_Isometric Drawing

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