BNG 101 – Engineering Graphics Slide Set 5 – Dimensioning I (Read Planchard 3-1 to 3-18)
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BNG 101 – Engineering Graphics
Slide Set 5 – Dimensioning I
(Read Planchard 3-1 to 3-18)
Objectives
Dimensioned drawing (SolidWorks)
Aspects of good dimensioning
1) Technique of dimensioning – standard appearance of lines, arrowheads, etc.
2) Placement of dimensions – legible, easy to find, easy to interpret
3) Choice of dimensions – function; ease of manufacturing
Aspects of good dimensioning
1) Technique of dimensioning – standard appearance of lines, arrowheads, etc.
2) Placement of dimensions – legible, easy to find, easy to interpret
3) Choice of dimensions – function; ease of manufacturing
Tolerance is the actual amount that the feature is allowed to vary from what is specified by the drawing. Example: All tolerances +/- 0.02 inch unless otherwise noted.
Dimensioning systems
U.S. (IPS) • uses decimal inch values • No zero to the left of the decimal for
values <1 inch • Trailing zeros are used
Metric (MMGS) • Requires all measurements to be in mm • “mm” label not needed on each
dimension • No trailing zeroes are used
Arrowhead placement
• Order of preference below based on how much space is available
Arrowheads
Geometric breakdown
1) Size dimensions (show sizes of simple geometric shapes)
2) Location dimensions (locate elements with respect to one another)
Geometric breakdown
1) Size dimensions (show sizes of simple geometric shapes)
2) Location dimensions (locate elements with respect to one another)
Size dimensions
• Two of the dimensions usually placed on the principal (front) view • Third dimension located on one of the other two views
How to: dimension and extension lines
Example 1 for do’s and don’ts
• How should the below dimensioning be adjusted (do a rough sketch on your paper)?
Example 2 for do’s and don’ts
Other dimension placements
Other dimension placements
Lines used in dimensioning
Practice exercise
Dimensioning by geometric breakdown
Dimensioning by geometric breakdown
Leader lines
Dimensioning cylinders – Example 1
Dimensioning cylinders versus holes
Practice exercise
• Fill in the missing dimensioning elements (hint: there is a hole and cylinder in the object – apply the rules we just learned!)
Superfluous dimensions – I
Superfluous dimensions – II
Pages 3-10 to 3-11 in Planchard text – additional practice exercises
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