Engineering Graphics IV Prof. Paul Kurowski October 30, 2012

Engineering Graphics IV Section Views Auxiliary Views Dimensioning Tolerancing

Section Views

Section Views Clearly show interior features Avoid confusing hidden lines

Cutting Planes Cutting planes define section views Lines of sight are perpendicular to the cutting plane Section views are parallel to cutting plane and perpendicular to lines of sight Objects shown in true size Cut surface is cross-hatched

Cutting Plane Lines Show where cutting plane passes through object Represent edge view of cutting plane Appear in views adjacent to section view

Full Section

Half Section

Offset Section

Broken Out Section

Sketch Section View

Solution E-drawing

Sketch Section View

Solution

Cross Hatching (Section Lines) General symbol (cast iron) used for most purposes and for sketching Section lines are normally drawn at 45° from the horizontal but can be changed for adjacent parts in the same section Normally section lines are not shown on thin parts Components like bolts are usually not sectioned

Cast Iron/ B) Sound C) Thermal General Insulation Insulation D) Water E) Steel F) Titanium/ Refractory Material G) Concrete H) Wood (across/along grain)

Auxiliary Views

What is an Auxiliary view? It is an extra view of an object It is used when the 6 principal views don’t describe an object (or some of its features) clearly or completely - in particular inclined features It is used to show the true lengths of lines It is used to show the true size of planes

Why use an Auxiliary View? None of these views shows the angled face in true size and shape.

An extra view is needed.

Constructing an auxiliary view It is an orthographic projection Lines of sight are perpendicular to the plane of the feature (or object) The projection plane is perpendicular to the lines of sight and parallel to the plane of the feature

Auxiliary Views

- Dimension on true size and shape views only - Use Auxiliary views if necessary YES

Question Which of the following is NOT true of an auxiliary view? They are used to show the true size and shape of features They are orthographic projections They are used to replace the traditional multiviews They are used when the traditional multiviews do not fully describe the object

Question Which of the following is NOT true of an auxiliary view? They are used to show the true size and shape of features They are orthographic projections They are used to replace the traditional multiviews They are used when the traditional multiviews do not fully describe the object

Dimensioning

Multi-view Drawing Specify: Size of features Location of features Details and notes

Dimensioning Dimensioning is necessary to specify: Size of features Location of features Details and notes for construction or manufacture Dimensioning is important in the communication of the design, from the designer to the manufacturer/contractor to the quality control inspection

Dimensioned Multi-View Drawing Units must be stated Typically inches or millimeters Mixed dimensions sometimes used

Terminology and Standards Leave gap Note arrow direction Limits indicate tolerance

Terminology and Standards Use diameter for circles, radius for arcs Show extra dimensions as reference only (or better, omit) Plus/minus indicates tolerance

Question Why are dimensions used? To specify the size of features To specify the location of features To specify details and notes for construction or manufacture To fully communicate the design All of the above

Question Why are dimensions used? To specify the size of features To specify the location of features To specify details and notes for construction or manufacture To fully communicate the design All of the above

Good Drafting Practices Dimensioning

Show all necessary views Make sure center lines are shown in all views! Bottom view shows important features

Make sure views are aligned NO YES

Don’t dimension hidden lines NO Dimension visible lines if possible YES

Dimension to centre lines of cylindrical features and holes Remember to show centre lines! NO YES

Dimension the most descriptive view

Don’t over or under-dimension Show necessary dimensions exactly once All dimensions can be derived from given dimensions Don’t show the same dimensions different ways

Don’t over-dimension YES NO

Don’t crowd dimensions YES NO

Extension lines should not cross dimension lines YES

- Dimension on true size and shape views only - Use Auxiliary views if necessary YES

Add Dimensions

More than one solution is possible

Add Dimensions

Solution

Add Dimensions

Solution