layouts and lettering chapter 2. 2 technical drawing 13 th edition giesecke, mitchell, spencer, hill...
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Layouts and Lettering
Chapter 2
2Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Objectives
• Identify six types of technical drawings based on the projection system they use
• Identify the line patterns used in technical drawings and describe how they are used
• Read and measure with the architect’s scale, engineer’s scale, and metric scale
3Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Objectives (cont.)
• Identify standard drawing media and sheet sizes
• Add lettering to a sketch• Fill in a standard title block with
the appropriate information• Lay out a drawing sheet
4Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Understanding Projections
• Behind every 2D drawing of an object is a space relationship involving the object and three “imagined” things:• The observer’s eye or station point• The plane of projection• The projectors
• Also called visual rays or lines of sight
5Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Types of Projection
• There are two main types of projection• Perspective projection – the
projectors come together at the station point• Perspective drawings represent objects
as we see them • Parallel projection – the projectors are
parallel
6Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Types ofProjection
7Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Types of Projection
• Orthographic projections are a type of parallel projection• Orthographic (right angle) projections
have parallel projectors that are perpendicular to the plane of projection
• In orthographic projection objects can be presented at true size or scaled at a proportion of their true size
8Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Types of Projection
• Oblique projection – when projectors are parallel to each other but are at an angle other than 90 degrees to the plane of projection
9Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Types of Projection
• Technical drawings of 3D objects usually use one of four standard types of projection• Multiview • Axonometric (isometric)• Oblique• Perspective
10Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Types of Projection
• Multiview projection – shows one or more necessary views of an object• There are two systems used to arrange
the views:• Third angle projection• First angle projection
• Axonometric, oblique, and perspective sketches show objects pictorially
11Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Types ofProjection
12Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Types of Projection
13Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Drawing Vocabulary
• Drawing lines – projected line drawings use specific line patterns to represent object features
• Lettering – the shapes of letters are described as part of drawing standards
• Measurement systems – both the metric system and U.S. customary units may be used
14Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Drawing Vocabulary
• Scale – to clearly convey important information about particularly large or small objects, appropriate sheet size and scale must be selected
• Title blocks – company information, drawing scale, sheet size and other information is included in a standard title block
15Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Alphabet of Lines
• The meaning of each line on a technical drawing is indicated by its width and its particular line style
• All lines should be uniform in width and darkness
16Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
17Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Freehand Lines
• The main difference between a CAD drawing and a freehand sketch is in the appearance of lines
• Freehand lines show freedom and variety but, aside from construction lines, should be dark and clean
18Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Good and Poor Line Technique
19Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Measurement Systems
• U.S. Customary Units• Based on inch-foot and yard
measurements• Drawings with these units still follow
ANSI/ASME standards• Drawing units must be clearly stated
on the drawing
20Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Measurement Systems
• The metric system• This is the International System of
Units, commonly referred to as SI• The primary unit of measurement for
engineering drawings and design in the mechanical industries is the millimeter (mm)
• Secondary units are the meter (m) and kilometer (km)
21Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Drawing Scale
• Drawing scale is the reduction or enlargement of the size of a drawn object relative to the real object• Scale is often determined on the size
of drawing sheet used• Scale is stated as a ratio of the
number of drawing units to the number of actual units
22Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Specifying the Scale on a Drawing• There are several acceptable
methods to note scale on a drawing• For example, a part that’s shown on
the paper at half its actual size, the scale may be listed in one of these ways:• SCALE 1:2• SCALE ½• SCALE .5
23Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Scales
• Scales are measuring tools used to quickly enlarge or reduce drawing measurements
• Types of scales include:• Metric• Engineers’ • Decimal• Mechanical engineers’• Architects’
24Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Lettering
• Lettered text is often necessary to describe an object or to provide detailed specifications
• Lettering should be legible, easy to create, and use appropriate styles
25Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Lettering
• The creation of neat freehand lettering has three necessary aspects:• Knowing the proportions and forms of
the letters• Spacing of letters and words for
legibility• Practice
26Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Lettering
• CAD drawings typically use a Gothic lettering style but often use a Roman style for titles
• When lettering a CAD drawing, it is advisable to not use more than two fonts within the same drawing for clarity
27Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
The Computer as a Drafting Tool• Most technical drawings are
created using CAD• Advantages of CAD include:
• Accuracy• Speed• The ability to present spatial and
visual information in a variety of ways
28Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
The Computer as a Drafting Tool• The advantages of CAD do not
eliminate the need for drawings to be easily and accurately interpreted
• The same general concepts and drafting standards apply to CAD as to drawings created by hand
29Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Sketching and Drawing Media• There are many media available
for sketching and drawing purposes including:• Sketch pads and notebooks• Grid paper• Isometric paper• Polyester film• Coated sheets of aluminum
30Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Standard Sheet Sizes
31Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Standard Layout Elements
• Margins and borders• Zones• Typical letter sizes• Title block
32Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Planning Your Drawing or Sketch• When laying out a drawing sheet
you will need to consider:• Size and scale of the object• Sheet size• Measurement system• Space necessary for notes and title
block