Dimensioning

1
Dimensioning
Ch. 9
2
Dimensions

• Dimensions are used to describe the sizes and
  relationships between features in your drawing.
• Dimensions are used to manufacture parts and to
  inspect the resulting parts to determine if they
  are acceptable.
• Proper dimensioning increases clarity of the
  drawing and reduces ambiguity
• ANSI/ASME Y14.5M-1994 is the current standard.

3
Standard Practices

• Criteria of designs dimensioning
• Basic sizes and locations of features
• Details for manufacturing
• Rules for dimensioning include
• Lines, symbols, and abbreviations
• Size and location dimensions
• Placement of dimensions

4
Terminology

• Basic dimension
• Theoretically, considered the exact size,
  location or orientation.
• Reference dimension
• Provided for information only and not directly
  used in the fabrication of the part
• Tolerance
• Limits of size (The largest and minimum
  acceptable size)
• Plus and minus (The allowable positive and
  negative variance)
• Datum
• A theoretically exact point (Surface, plane,
  axis) used as a reference

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Terminology
6
Leaders
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Placement of dimensions
8
Placement of Dimensions
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Stagger Dimension Values
Rule
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Dimensioning Systems

• Unidirectional
• Read horizontally from bottom of sheet

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Dimensioning Systems
2. Aligned All numerals, figures and notes be
aligned with dimension lines
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Dimensioning Systems
3. Tabular Coordinate Size and location
dimensions from datums or coordinates are given
in a table identifying features in the drawing.
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Dimensioning Systems
4. Chart Used when dimensions change depending
on a specific application
14
Dimensioning Cylinders
15
Dimensioning Holes
16
Using Diameter Symbol
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Locating Holes