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Standard Practice for
Engineering Drawings
Introduction to
Mechanical Engineering
Fall 2004
Created by:
P.M. Larochelle
Standard Sheets
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For layout designations, title blocks, revision
blocks, and list of materials blocks see the
front inside cover of the text.
Sheet size selection:
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For simple parts use small sheets
For complex parts use large sheets
Standard Sheets
ANSI (US)
(in)
ISO (International)
(mm)
A (8.5x11.0)
A4 (210x297)
B (11.0x17.0)
A3 (297x420)
C (17.0x22.0)
A2 (420x594)
D (22.0x34.0)
A1 (594x841)
E (34.0x44.0)
A0 (841x1189)
Title Blocks
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Title Blocks record important info regarding
the drawing:
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–
–
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Part name & number
Names of the persons that: created, modified, and
approved the drawing
Dates that the drawing was created & revised
Company Name
The scale of the drawing
Etc.
Title Blocks
Scale
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The scale of the drawing is the ratio of the
size of the object as drawn to the actual size.
The scale you chose depends upon both the
size of the object and the sheet size.
When practical it is always preferable to
show parts and assemblies at full scale (I.e.
actual size).
Scale

Scales are denoted by two numbers
separated by a colon e.g. 1:10
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On the left is the length on the drawing
On the right is the actual length on the object
Always use integer scales
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Use 3:2 instead of 1.5:1
Scale

Some scales can be denoted by text
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1:1 = FULL SCALE = FULL SIZE
1:2 = HALF SCALE = HALF SIZE
2:1 = DOUBLE = 2x
Standard Scales
ANSI (US)
ISO (International)
1:1
1:1
1:2
1:2
1:4
1:5
1:8
1:10
1:10
1:20
Geometry
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A working knowledge of the fundamental
principles and terminology of geometry is
essential to create engineering drawings.
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We will now review the basic concepts and
geometric elements commonly encountered in
engineering drawing.
Points
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A point represents a location. It has zero
dimensions; no length, width, or depth.
A point is always defined by the intersection
of two line segments- never by a “dot”.
Lines
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Euclid defined a line as “that which has
length without breadth”. In Euclid’s time and
for many hundreds of years thereafter any
element- straight or curved that had no
breadth was called a line (e.g. french curves,
splines, etc.). Today, we define a line as
being straight. A line represents a point and
a direction. It has one dimension- length; it
has no width or depth.
Lines
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A line has infinite length whereas a line
segment is a line of finite length.
In technical drawing we are always
concerned with line segments. Therefore we
abbreviate the term line segment to “line”.
The term “line” in technical drawing always
refers to a line segment.
Lines
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Parallel lines are pairs of lines that share the
same direction but different points.
Perpendicular lines are pairs of lines that
share the same point but have orthogonal
directions. In sketches you may denote two
perpendicular lines with a box at their
intersection- but never in drawings.
Angles
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An angle is formed by two intersecting lines.
The common unit of measure for angles is the
degree.
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There are 360 degrees in a full circle, 60 minutes in a
degree, and 60 seconds in a minute. Example: 37o26’10’’ is
read as “37 degrees, 26 minutes, and 10 seconds.
Alternatively, angles can be denoted by decimal degrees.
Example 37.43611 (degrees).
Angles
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Supplementary angles sum to 180 (degrees).
Complementary angles sum to 90 (degrees).
An acute angle measures less than 90
(degrees).
An obtuse angle measures more than 90
(degrees).
Triangles
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A triangle is a
planar figure
bounded by three
line segments.
The sum of the
interior angles in a
triangle is 180
(degrees).
Polygons
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A polygon is any planar figure bounded by
straight lines- a triangle is a 3-sided polygon.
If the polygon has equal angles and sides then
it is a regular polygon.
Circles
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A circle is a planar figure formed by the set of all
points equidistant from a given point.
The circumference is the distance around the
circle.
The radius is the distance from the points on the
circle to the given point.
Solids
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Three-dimensional solids bounded by plane
surfaces are called polyhedra.
The plane surfaces that define a polyhedra are
called faces.
If the faces are regular polygons then the solid is
called a regular polyhedra.
Solids
References
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Chapters 3&4 of Modern Graphics
Communication by Giesecke, Mitchell,
Spencer, Hill, Dygdon, Novak, and Lockhard,
3rd edition. Prentice-Hall, 2004.
Technical Drawing by Giesecke, Mitchell,
Spencer, Hill, Dygdon, and Novak, 9th edition.
Macmillan, 1991.