Engineering Graphics IV

Prof. Paul Kurowski

October 30, 2012

Engineering Graphics IV

Section Views Auxiliary Views

Dimensioning Tolerancing

Section Views

SectionViews

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 PlaneLines

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

A) 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

NO YES

Question

Which of the following is NOT true of an auxiliary view?A. They are used to show the true size and shape of

features

B. They are orthographic projections

C. They are used to replace the traditional multiviews

D. 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?A. They are used to show the true size and shape of

features

B. They are orthographic projections

C. They are used to replace the traditional multiviews

D. 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?A. To specify the size of features

B. To specify the location of features

C. To specify details and notes for construction or manufacture

D. To fully communicate the design

E. All of the above

Question

Why are dimensions used?A. To specify the size of features

B. To specify the location of features

C. To specify details and notes for construction or manufacture

D. To fully communicate the design

E. All of the above

Good Drafting Practices Dimensioning

Show all necessary views

Bottom view shows important

features

Make sure center lines

are shown in all views!

Make sure views are aligned

NO YES

Don’t dimension hidden lines

NO

YESDimension visible lines if possible

Dimension to centre lines of cylindrical features and holes

NO YES

Remember to show centre lines!

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

NO YES

Don’t crowd dimensions

NO YES

Extension lines should not cross dimension lines

NO YES

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

NO YES

Add Dimensions

Solution

More than one solution is possible

Add Dimensions

Solution

Add Dimensions

Solution