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Size and Shape II. Bill Cowan & R. Cash. Advanced Dimensioning And Sectioning. Datum Dimensioning Dual Dimensioning Section Views. Datum Dimensioning. Dimensions should be given from finished surfaces. Datum dimensioning is when dimensions originate from one surface or point.
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Size and Shape II Bill Cowan & R. Cash
Advanced Dimensioning And Sectioning • Datum Dimensioning • Dual Dimensioning • Section Views
Datum Dimensioning • Dimensions should be given from finished surfaces. • Datum dimensioning is when dimensions originate from one surface or point.
Dual Dimensioning • Allows two types of dimensioning units to be used. (Metric and American Standard) • Brackets are used to identify secondary dimension.
Review Of Dimension Rules • Always give dimensions to a shape. • Avoid dimensioning to hidden lines. • Never draw an unnecessary view. • Dimension holes in the view where they appear as a circle. • Give hole sizes as a note. • Dimension An Arc by giving a radius
Review Of Dimensioning • A dimension should be attached to only one view. • A center line should not extend from view to view. • Dimension fillets and rounds with a note if possible. • A cylinder is dimensioned by giving both its diameter and length in the same view.
Section Views • Full Section • Cutting Plane Line • Section Lines • Treatment Of Hidden Lines • Dimensioning
Section Lines indicate what area has been cut. Full Section Cutting Plane Shows Line Of Sight.
Review • Why do we draw a section? • What is a full section? • What is a cutting plane line? • What are section lines? • How do we treat hidden lines? • When do you omit a cutting plane line?
Half Section • Used on Symmetrical Objects • Cutting Plane Line does not pass completely through the object. • Unnecessary hidden lines are omitted.
Half Section Cutting Plane extends through half the object.
Aligned Section • Allows you to section angled elements • The cutting plane is bent so as to pass through those features. • The angled features are revolved so as not to be projected foreshortened.
Aligned Section Ribs, Keyways, Webs, and Gear Teeth are not sectioned.
Sectioning Large AreasSectioning Parts In AssemblySectioning Thin Parts
Offset Section • Sections through irregular objects. • For features that do not lie in a straight line. • Allows bending of the Cutting Plane line.
Cutting Plane Line bends at 90 degrees to include features not in a straight line.