chapter 05 pictorial sketching

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Chapter 5 Pictorial Sketching

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Chapter 5

Pictorial Sketching

Objectives

Be able to explain the difference between an

axonometric projection and an oblique

projection.

Be able to explain the difference between an

isometric projection and an isometric

drawing/sketch.

Be able to create an isometric and oblique

sketches from an actual object and multiview

drawing.

Axonometric& ObliqueProjection

Axonometric Projection

AB

CD

Parallel & normalto picture plane

Lineof

sightA

B

CD

Axonometric ProjectionType of axonometric drawing

a

b c2. Dimetric Two angles are equal.

b

a

c3. Trimetric None of angles are

equal.

a

b c1. Isometric All angles are equal.

AB

CDA

B

C

D

Axonometric axis

Axonometric axis

Axonometric axis

A

BC

D

Lineof

sight

Parallel & obliqueto picture plane

Oblique Projection

A

D

C

B

Oblique Projection

A

D

C

B

B

C D

A

Oblique drawing angle

30o45o 60o

Type of Oblique drawing

45o 45o

1) Cavalier 2) Cabinet

Fullscale Half

scale

Isometric Projection& Isometric drawing

Rotate 45about vertical axis

Tilt forward (35o16’)

Isometric Projection

All edges foreshortenabout 0.8 time.

Isometric DrawingIsometric drawing is a drawing drawn on an isometric

axes using full scale.

Isometric projection(True projection)

Isometric drawing(Full scale)

Forshorten

Full scale

Positions of Isometric AxesIsometric axes can be arbitrarily positioned to create

different views of a single object.

Regularisometric

Reverse axisisometric

Long axisisometric

View point is lookingdown on the top ofthe object.

View point is lookingup on the bottom ofthe object.

View point is lookingfrom the right (or left)of the object.

Distance in Isometric Drawing

Isometric line is the line that run parallel to

any of the isometric axes.

Isometric axes

True-length distances are shown along

isometric lines.

Nonisometric lines

Isometric Sketching

2. Define an isometric axis.

3. Sketching the enclosing box.

4. Estimate the size an and relationship of each

details.

5. Darken all visible lines.

1. Place the object in the position which its shape

and features are clearly seen.

Sketch from an actual object

STEPS

1. Positioning object.

2. Select isometric axis.

3. Sketch enclosing box.

4. Add details.

5. Darken visible lines.

Sketch from an actual object

1. Positioning object.

2. Select isometric axis.

3. Sketch enclosing box.

4. Add details.

Note In isometric sketch/drawing), hidden lines are omitted

unless they are absolutely necessary to completely

describe the object.

Sketch from an actual objectSTEPS

5. Darken visible lines.

1. Interprete the meaning of lines/areas in

multiview drawing.

2. Locate the lines or surfaces relative to isometric

axis.

Sketch from multiview drawing

Front View

Top View

Side View

Example 1 : Object has only normal surfaces

Bottom View

Bottom

FrontSide

SideFront

Top

Regular

Reverse

WD

H

H

DW

Example 2 : Object has inclined surfaces

W

H

D

y

x Front View

y

x

Nonisometric line

Nonisometric line

A

A x

y

x

xB

B

AB

C

C

C

x

y

Example 3 : Object has inclined surfaces

A

A

B

B

C D

E

D

EF

F

x

y

Front View

Regular

C

Example 4

Reverse

Circle & Arc in IsometricIn isometric drawing, a circle appears as an ellipse.

2. Construct an isometric square.

3. Sketch arcs that connect the

tangent points.

Sketching Steps

1. Locate the center of an ellipse.

Circle & Arc in Isometric

3. Construct a perpendicular

bisector from each tangent point.

4. Locate the four centers.

5. Draw the arcs with these centers

and tangent to isometric square.

Sketching Steps

Four-center method is usually used when drawn an

isometric ellipse with drawing instrument.

2. Construct an isometric square.

1. Locate the center of an ellipse.

Example 5

Irregular Curve in Isometric

1. Construct points along the

curve in multiview drawing.

2. Locate these points in the

isometric view.

3. Sketch the connecting lines.

Steps

ObliqueSketching

Object Orientation Guidelines

Place complex features (arc, hole, irregular shapesurface parallel to frontal plane.

Object Orientation GuidelinesThe longest dimension of an object should beparallel to the frontal plane.

GOOD

WORSE

GOOD

WORSE

Object Orientation Guidelines

Which orientation is better ?

D

45

ESTIMATE DEPTHESTIMATE LINES

Sketch from actual object

Sketch from multiview drawing

Sketch from multiview drawing

AB

C

D

E

Sketch from multiview drawing

AB

C

D

E

Sketch from multiview drawing

AB

D

E

C

Sketch from multiview drawing

AB

D

E

C

Sketch from multiview drawing