Chapter 14
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CHAPTER 14. Pictorial Drawings and Technical Illustrations. Learning Objectives. Draw three-dimensional objects using 3-D coordinates Construct objects using isometric, diametric, or trimetric methods Construct objects using oblique drawing methods. Learning Objectives.

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CHAPTER 14

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CHAPTER 14

Pictorial Drawings and Technical Illustrations


Learning Objectives

  • Draw three-dimensional objects using 3-D coordinates

  • Construct objects using isometric, diametric, or trimetric methods

  • Construct objects using oblique drawing methods


Learning Objectives

  • Draw objects using one-, two-, or three-point perspective

  • Apply a variety of shading techniques to pictorial drawings

  • Given an orthographic engineering sketch of a part or assembly, draw the part in pictorial form using proper line contrasts and shading techniques


Pictorial Drawings

  • Often accompany 2-D orthographic multiviews

    • Provide a realistic 3-D view

    • Help improve visualization

  • Now created using CADD or illustration programs

  • ASME Y14.4M, Pictorial Drawing standard


Pictorial Drawings

  • Useful for a variety of applications

  • Clarify basic and complicated engineering designs

  • Help designers and engineers work out spatial problems

  • Most often the basis for technical illustrations


Pictorial Drawings


Uses of Pictorial Drawings

  • Design

  • Instruction manuals

  • Parts catalogs

  • Advertising literature

  • Technical reports

  • Presentations

  • Assembly

  • Construction


Isometric Projections and Drawings

  • Equal (iso) measure (metric)

  • Simplest form of axonometric projection

  • Single scale for all axes


Isometric and Nonisometric Planes


Regular Isometric

  • Most common

  • View the top of the object and the object from either side


Reverse Isometric

  • View the bottom of the object


Long-Axis Isometric

  • Common for long objects


Isometric Construction: Box or Coordinate Method

  • Most common form of isometric construction

  • Used on objects that have angular or radial features


Isometric Construction: Centerline Layout Method

  • Used on objects with many circles and arcs

  • Circles in isometric are isometric ellipses


Isometric Circles and Arcs


Establishing Isometric Intersections


Drawing Isometric Sections


Drawing Isometric Threads

  • Equally spaced elliptical arcs

  • Detailed thread representation


Drawing Isometric Spheres


Dimetric Pictorial Representation

  • Form of axonometric projection

  • Two different scales for measurement

  • Missing image – go to page 566


Trimetric Pictorial Representation

  • Most involved form of axonometric projection

  • Three different scales for measurement


Exploded Pictorial Drawings

  • Exploded assembly

  • Show the relationship of parts in a realistic manner

  • Commonly used in:

    • Parts catalogues

    • Owner's manuals

    • Assembly instructions


Exploded Pictorial Drawings

  • Isometric drawings most common

  • Can include centerlines between part and subassembly axes

  • Can use solid extension lines between non-cylindrical features, parts, and subassemblies

  • Can include balloons


Exploded Pictorial Drawing


Oblique Drawing

  • Shows three faces of the object

  • Useful if one face of an object needs to be shown flat


Cavalier Oblique


Cabinet Oblique


General Oblique


Perspective Drawings

  • Most realistic pictorial illustration

  • Show depth and distortion perceived by the human eye

    • Objects appear smaller the farther away they are until they vanish at a point on the horizon

      • One-point or parallel perspective

      • Two-point or angular perspective

      • Three-point perspective


General Perspective Drawing Concepts


One-Point Perspective

  • Plan view is oriented so the front surface of the object is parallel to the picture plane

  • Elevation view is placed below and to the right or left of the plan and rests on the ground line

  • Used most often when drawing interiors of rooms


Two-Point Perspective

  • Two principal planes are at an angle to the picture plane

  • Two vanishing points provide another dimension to the depth of the perspective

  • Most popular form of perspective drawing

    • Exteriors of houses and small buildings

    • Civil engineering projects

    • Machine parts (occasionally)


Three-Point Perspective

  • Time consuming to construct

  • Often occupy a considerable area on the drawing sheet

  • Used to illustrate objects having great vertical measurements, such as tall buildings


Drawing Circles and Curves in Perspective

  • Circles in perspective typically appear as ellipses

  • Any circle on surface parallel to the picture plane appears as a circle

  • Construction using the coordinate method


Basic Shading Techniques

  • Line-contrast shading

  • Straight-line shading

  • Block shading

  • Stipple shading


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