Dimensioning is a method of accurately communicating size information about objects and structures so they can be produced. After completing this chapter you will be able to apply the standard dimensioning practices for mechanical drawings, differentiate current ANSI standards and past practices for dimensioning.
Trang 1Dimensioning
Trang 2Definition
Size and shape
Position
Surface texture or
Geometric characteristic
Of a feature
A dimension is a numerical value that defines the:
Trang 3Millimeters (mm) in the metric system
Inches in the English system
The default dimensional units in most
CAD systems are:
NOTE:
• Dimensions in millimeters typically expressed as whole numbers
• Dimensions in inches typically expressed to two
Trang 4Leader – Line (w/ arrow) drawn from a feature to a note
Reference dimension – Numerical value provided for
information only and not used in fabrication of the part
NOTE: Dimension text heights are typically 3
mm, and are uniform throughout the drawing
Trang 5Dimensioning Guidelines for Prisms-1
Do not repeat dimensions
Dimension most descriptive
view of feature being
dimensioned
Dimension between views
Omit one intermediate
dimension
Smaller dimensions inside
of larger dimensions
Extension lines may cross
object lines and other
Trang 6Dimensioning Guidelines for Prisms-2
Avoid dimensioning
inside an object
Dimension to visible
object lines, not to
hidden lines
Trang 7Dimensioning Rules/Guidelines for Cylinders and Arcs
Dimension diameter
of cylindrical parts in
their rectangular
views
Dimension diameter
of cylindrical holes in
their circular views
Dimension radius of
fillets and rounds
(180 degrees or
less)
Trang 8C’est tout!