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Lecture 04

Interpreting and Depicting Geometry in Orthogonal Projections

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HW Assignment 03

MGC: Reading:

Finish CH 5Start CH 6

HW 03 MGC CH5:Exercises p. 207 :

5.7, # 4 (note: numbers are above object)

Exercises p.210: 5.19 (note: numbers are below object)

Exercises p.211: 5.28 (note: numbers are below object)

Note: NO borders & title blocks required on HW No more than two sets of part views per page.

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Line Interpretations

Construction Line Purpose:

Locate intermediate / transition points and extent of features

Weight: light, thick*

Style: semi-solid, and do not

reproduce

Visible (Object) Line Purpose:

show extent of features visible in the current view

Weight:dark, thick

Style:solid, crisp ends

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Line Interpretations

Center Line Purpose:

show axis and extent of symmetry

Weight: dark, thin

Style: long dash, short dash

at center, long dash

Hidden Line Purpose:

show extent of features hidden by other features

Weight:dark, thin

Style:short, even dashes

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Line Interpretations

(Short) Break Line Purpose:

show hidden features in detail for clarity

Weight: dark, thick

Style: solid, semi-rough

Section Line Purpose:

show cross-section of material

Weight:dark, thin

Style:solid, angled to

adjacent visible lines

Note: For demonstration only. Prefer the use of conventional breaks in practice (see CH 6).

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Views of Surfaces & Edges

Normal Surfaces Parallel to one plane of

projection and perpendicular to adjacent projections (appearing as a true sized line)

Inclined Surfaces Perpendicular to one

plane (appearing as a line of true size) and are inclined to adjacent projection planes

Oblique Surfaces Inclined to all planes of

projection and cannot appear as a true size edge in any standard view

Normal Edges Perpendicular to one

plane of projection, and appears there as a point

Are parallel to adjacent projection planes and appear in true length

Inclined Edges Parallel to one plane of

projection, where they appear in true size, but are inclined to adjacent projection planes

Oblique Edges Inclined to all planes of

projection, and cannot be shown in true length since they are never parallel to a standard projection

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Types of Surfaces

Normal Surfaces

Inclined Surfaces

Oblique Surfaces

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Types of Edges

Normal Edges

Inclined Edges

Oblique Edges

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True Length & True Angle

True Length Edges

Foreshortened Edges

True Angles

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Planar Geometry

Points Could represent a vertex of three or more surfaces Could represent the point view of an orthogonal edge

Lines Could represent the intersection of two surfaces Could represent the edge view of an orthogonal surface Could represent the extent of a curved surface

Angles Appear in true size only if the angle (intersection of two

edges) lies in a normal plane (in a plane parallel to a projection)

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Intersections & Tangencies

Intersections Are sharp transitions

where adjacent or machined surfaces meet

Are shown as lines in profile and other views

Tangencies Are smooth transitions

from a surface to an adjacent curve

Are shown as lines in profile

Are not shown as lines in other views, unless:

They transition to a normal surface

They are runoutsThey are conventional

edges

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Runouts & Conventional Edges

Rounds Are exterior rounded

intersections

Fillets Are interior rounded

intersections

Runouts Are small curves used

to represent the connection of a planar to a curved surface

(See Fig. 5.14 – 5.16, p.190 – 191)

Conventional Edges For certain types of

rolled / cast forms, the smooth transitions are eliminated to clarify the shape

(See Fig. 5.17 p.191)

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Scales

Revolution Conventions Odd, rotational symmetry

is depicted, not projected (See Figs. 5.34, and 5.35,

pp. 198)

Drawing Scale Specify drawing scale in

the title block, i.e.: Scale 1 : 5

Left side of colon are local drawing units

Right side of colon are real life units

Never measure a drawing to obtain a dimension

Never omit a required dimension from a drawing

Measuring Scales Types of Measuring

ScalesMetric ScalesInch-Foot ScalesEngineer’s ScalesArchitect’s ScalesMechanical Engineer’s

ScalesPatternmaker’s Scales

Measuring Scales are only used for taking measurements

Never use a scale as a straight edge for drawing