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7 Pictorial Sketching

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October 25, 2022

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Pictorial Sketching

Pictorial Drawing

A Pictorial drawing provides a 3D image to help understand the shape of an object or to assist in interpreting a drawing.

There are 3 main ways to draw a pictorial drawing

1. Isometric (Axonometric)
   
2. Oblique
   
3. Perspective
   

Three Types of Pictorial Sketches

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 sketches from an actual object and multiview drawing.

Axonometric & Oblique Projection

Axonometric Projection

Type of axonometric drawing

Axonometric axis

a

1. Isometric
2. All angles are equal.
   

   

   c
   

   

3. Dimetric Two angles are equal.
   

    

   

   Axonometric axis
   

4. Trimetric None of angles are
   

equal.

Oblique Projection

Oblique drawing angle

Type of Oblique drawing

1) Cavalier 2) Cabinet

Isometric Projection & Isometric drawing

Isometric Projection

Rotate 45° about vertical axis

Tilt forward

(35o16‘)

All edges foreshorten

about 0.8 time.

Isometric Drawing

Isometric drawing is a drawing drawn on an isometric axes using full scale.

Isometric projection

(True projection)

Full scale

Positions of Isometric Axes

Isometric axes can be arbitrarily positioned to create different views of a single object.

Regular isometric

View point is looking down on the top of the object.

Reverse axis isometric

View point is looking up on the bottom of the object.

Long axis isometric

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

Isometric Sketching

Sketch from an actual object

1. Place the object in the position which its shape and features are clearly seen.
   
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.
   

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

STEPS

1. Positioning object.
   
2. Select isometric axis.
   
3. Sketch enclosing box.
   
4. Add details.
   
5. Darken visible lines.
   

   Note In isometric sketch/drawing), hidden lines are omitted unless they are absolutely necessary to completely describe the object.

   Sketch from multiview drawing
   

   Interprete the meaning of lines/areas in multiview drawing.
   

   1. Locate the lines or surfaces relative to isometric axis.
      

Example 1 : Object has only normal surfaces

Front View

Side View

Example 2 : Object has inclined surfaces

Nonisometric line

Example 3

Regular

Front View

FIn isometric drawing, a circle appears as an ellipse.

Circle & Arc in Isometric

Sketching Steps

1. Locate the center of an ellipse.
   
2. Construct an isometric square.
   
3. Sketch arcs that connect the tangent points.
   

Example 4

Irregular Curve in Isometric

Steps

1. Construct points along the
   

   curve in multiview drawing.
   

2. Locate these points in the
   

   

   
   

   isometric view.
   

3. Sketch the connecting lines.