dimensioning chapter 9. 2 technical drawing 13 th edition giesecke, mitchell, spencer, hill dygdon,...
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Dimensioning
Chapter 9
2Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Objectives
• Use conventional dimensioning techniques to describe size and shape accurately on an engineering drawing
• Create and read a drawing at a specified scale
• Correctly place dimension lines, extension lines, angles, and notes
3Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Objectives (cont.)
• Use aligned and unidirectional dimensioning systems
• Dimension circles, arcs, and inclined surfaces
• Identify precision ranges for typical manufacturing operations
• Apply finish symbols and notes to a drawing
4Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Objectives (cont.)
• Dimension contours• Use standard practices for
dimensioning prisms, cylinders, holes, curves
• List practices for dimensioning a solid model as documentation
• Identify guidelines for the do’s and don’ts of dimensioning
5Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Understanding Dimensioning• Drawings for products must be
dimensioned so that production personnel all over the world can make mating parts that will fit properly when assembled or when used to replace parts
6Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Aspects of Good Dimensioning• Dimensions are given in the form
of distances, angles, and notes regardless of the dimensioning units being used
• The ability to create good dimensions requires:• Technique of dimensioning• Placement of dimensions• Choice of dimensions
7Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Tolerance
• When a finished part is measured it may vary slightly from the exact dimension specified
• Tolerance is the total amount that the feature on the actual part is allowed to vary from what is specified by the dimension
8Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Lines Used in Dimensioning• Dimension line – a thin, dark, solid
line terminated by arrowheads, indicating the direction and extent of a dimension
9Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Lines Used in Dimensioning• Extension line – a thin, dark, solid
line that extends from a point on the drawing to which a dimension refers
10Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Lines Used in Dimensioning• Centerline – a
thin, dark line alternating long and short dashes commonly used in locating holes and other symmetrical features
11Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Using Dimension and Extension Lines• Shorter dimension lines are nearest
the object outline• Dimension lines should not cross
extension lines• A dimension line should never
coincide with or extend any line of the drawing
• Avoid crossing dimension lines when possible
12Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Using Dimension and Extension Lines
13Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Using Dimension and Extension Lines• Dimensions should be lined up and
grouped together as much as possible
14Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Using Dimension and Extension Lines• When extension lines or center
lines cross visible object lines, gaps should not be left in the lines
15Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Arrowheads
• Arrowheads indicate the extent of dimensions
• They should be uniform in size and style throughout the drawing
16Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Leaders
• A leader is a thin solid line directing attention to a note or dimension and starting with an arrowhead or dot
17Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Drawing Scale and Dimensioning• Drawings are usually made to a
scale which is indicated in the title block
• A heavy straight line should be drawn under any single dimension value that is not to scale• If an entire drawing is not prepared to a
standard, note NONE in the scale area of the title block
18Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Direction of Dimension Values and Notes• All dimension values and notes are
lettered horizontally and should read from the bottom of the sheet• The exception is when dimensioning
from a baseline as in coordinate dimensioning
19Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Direction of Dimension Values and Notes
20Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimension Units
• Dimension values are shown using the metric system or decimal inch values
• It is standard practice to omit millimeter designations and inch marks on drawings and note the units in the title block except when there is a possibility of misunderstanding
21Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimension Units
• Either meters or feet and inches and fractional inches are used in architectural and structural work • In U.S. structural and architectural
drafting, all dimensions of 1 foot or over are usually expressed in feet and inches
22Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Millimeter Values
• The millimeter is the commonly used unit for most metric engineering drawings• One-place millimeter decimals are
used when tolerance limits permit• Two or more-place millimeter
decimals are used when higher tolerances are required
23Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Decimal Inch Values
• Two-place decimals are typical when tolerance limits permit• In two-place decimals, the second
place preferably should be an even digit so that when the dimension is divided by 2 the results will still be a two-place decimal
24Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Rules for Dimension Values• Where the metric dimension is a
whole number, do not show a decimal point or a zero
• Where the metric dimension is less than 1mm, a zero precedes the decimal point
• Where the decimal-inch dimension is used, a zero is not used before the decimal point of values less than 1
25Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Rounding Values
• If the number following the rounding position is a 5, round to an even number
• If the number following the rounding position is less then 5, make no change
• If the number following the rounding position is more than 5, round up
26Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dual Dimensioning
• Dual dimensioning is used to show metric and decimal inch dimensions on the same drawing
27Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimension Symbols
28Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Placing Dimensions
• Never letter a dimension value over any line on the drawing
• In a group of parallel dimension lines, the dimension values should be staggered
• Do not crowd dimension figures into limited spaces making them illegible
29Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Placing Dimensions
• Place dimensions between views when possible, but only attached to a single view
• Dimensions should not be placed on a view unless doing so promotes the clarity of the drawing
30Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Placing Dimensions
• When a dimension must be placed in a hatched area or on the view, leave an opening in the hatching or a break in the lines for the dimension value
31Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Placing Dimensions
• Avoid dimensioning to hidden lines• Do not attach dimensions to visible
lines where the meaning is not clear• Notes for holes are usually placed
where you see the circular shape of the hole• An external cylindrical shape is
dimensioned where it appears rectangular
32Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Placing Dimensions
• Give dimensions where the contours of the object are defined
33Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Superfluous Dimensions
• All necessary dimensions must be shown but avoid giving unnecessary dimensions
• Do not repeat dimensions on the same view or on different views, or give the same information two different ways
34Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Superfluous Dimensions
35Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Angles
• You should dimension angles by specifying the angle in degrees and a linear dimension
36Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Arcs
• A circular arc is dimensioned in the view where you see its true shape by giving the value for its radius preceded by the abbreviation R
37Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Fillets and Rounds
• Individual fillets and rounds are dimensioned like other arcs• If there are only a few and they are
obviously the same size, giving one typical radius is preferred
• Fillets radii can also be given in a general note
38Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Size Dimensions: Prisms
39Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Size Dimensions: Cylinders
40Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Size Dimensions: Holes
41Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Various Shapes
42Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Curves
43Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Curved Surfaces
44Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Rounded-end Shapes
45Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Threads
46Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Tapers
47Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Dimensioning Chamfers
48Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Shaft Centers
49Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Dimensioning Keyways
50Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Dimensioning Knurls
51Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Finish Marks
• A finish mark is used to indicate that a surface is to be machined
52Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Surface Roughness
53Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Location Dimensions
54Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Location Dimensions
55Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Location Dimensions
56Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Location Dimensions
57Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
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Mating Dimensions
58Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Tabular Dimensions
59Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Coordinate Dimensioning
• Basic coordinate dimensioning practices are generally compatible with the data requirements for automated production
• A set of three mutually perpendicular datum or reference planes is usually required for coordinate dimensioning
60Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Coordinate Dimensioning
61Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Coordinate Dimensioning
62Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Machine, Pattern, and Forging Dimensions
63Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Sheet-Metal Bends
• In sheet-metal dimensioning, allowance must be made for bends
64Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Notes
• It is usually necessary to supplement the direct dimensions with notes
• Notes should be worded to allow only one interpretation
• Notes should be lettered horizontally
65Technical Drawing 13th EditionGiesecke, Mitchell, Spencer, Hill Dygdon, Novak, Lockhart
© 2009 Pearson Education, Upper Saddle River, NJ 07458.
All Rights Reserved.
Standards
• Dimensions should be given to make use of readily available materials, tools, parts, and gages
• The dimensions for many commonly used machine elements are standardized and can be obtained from standard manuals or catalogs