Download Technical Drawings

First Class
Technical Drawing
Class Objectives
•Explain the syllabus, grading and attendance policy.
•Explain the terminology of technical drawings
•Explain the concept of multiview drawing as it applies to simple objects.
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© Technical Drawing 101 with AutoCAD All Rights Reserved
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Note: It is the student's responsibility to inform the instructor when circumstances prevent him/her from attending class. When
a student believes that their absence qualifies as an excused absence, they should contact the instructor (preferably by email)
and request that the absence be excused and offer a reason(s) why they believe an excused absence is warranted.
© Technical Drawing 101 with AutoCAD All Rights Reserved
Smith, Ramirez and Schmidt
Examples of How Drawings are Graded:
What the student submitted:
Minus 5-Mistakes that would result in the part being manufactured incorrectly
(things that change the design intent) or leaving off information necessary to
manufacture the part.
-omitting a required dimension
-incorrectly noting a dimension value
-features that are not drawn or modeled to their true size
-features that are located incorrectly
-omitting visible line(s) of a feature
-omitting notation required to manufacture part (example: not specifying a material, or
specifying the wrong material).
-incorrect placement or orientation of multiviews (example: placing a top view below a
front view).
-failure to display parentheses around a reference dimension
Minus 3 – Mistakes affecting the precision of the part at manufacture (maximum
of 5 points if numerous similar errors-incorrect precision noted on dimension (example: dimension should read 2.000 but is
shown on drawing as 2.00)
-rounding error on a dimension (example: dimension should read 1.875 but is shown
on drawing as 1.88
Minus 2 – Mistakes that create problems for manufacturers
-omitting or improperly noting scale of drawing in title block
-omitting hidden or center line(s),
-lines projected incorrectly from one view to the next but not involving an incorrect
dimension
-part number in detail drawing does not match part number in balloon and/or parts list
-printing in color when monochrome is specified (or other printing error).
Minus 1-Minor Mistakes
-misspelled words
-capitalization mistake(s)
-LTscale problems (example: no gaps showing in center-lines (-2 max for multiple
instances)
-incorrect text height (-2 max for multiple instances of a specific mistake)
-incorrect placement of dimensions (-2 max for multiple instances of a same mistake)
-incorrect dimension spacing (-2 max for multiple instances of a same mistake)
-improper dimension style settings (-2 max for multiple instances of a same mistake)
-incorrect line weight, etc. (-2 max for multiple instances of a same mistake)
-not dimensioning a cylinder on its side view
-no date shown in title block
-incorrect sheet numbering, drawing number, or drawing name
-incorrect formatting of notes (example: notes that are not numbered, or text height of
notes does not match dimension text height)
What the instructor handed back:
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10% OFF EACH DAY AN ASSIGNMENT IS LATE AND IS NOT ACCEPTED AFTER 3 DAYS
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Architectural CAD Degree Plan
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Civil CAD Degree Plan
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Mechanical CAD Degree Plan
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Electronic CAD Degree Plan
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Interdisciplinary CAD Degree Plan
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Certificate Plans at ACC
Certificate Programs in Architectural and Engineering Computer Aided Design of vary in
length.
Four Areas of emphasis to choose from:
-General Certificate (36 Hours)
-Integrated Circuit Layout and Design (27 Hours)
-Civil (16 Hours)
-CAD Management (12 Hours)
Many students complete the Certificate requirements while fulfilling the requirements of
the Associate Degree.
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CAD Certificate Plans
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Today’s Lesson-Part 1: Technical Drawings
Introduction
Technical Drawings are the graphics and documentation (notes and specifications) used by
manufacturers to fabricate electronic and mechanical products, and by construction professionals to
produce architectural structures (houses and buildings) and civil engineering projects (roads, dams,
bridges).
Other terms often used to describe the creation of technical drawings are:
drafting,
engineering graphics,
engineering drawings,
and CAD (Computer Aided Design).
Technical drawing is not a new concept, there is archeological evidence suggesting that humans first
began creating crude technical drawings several thousand years ago.
Through the ages, architects and designers, including Leonardo Da Vinci, created technical drawings.
But a French mathematician named Gaspard Monge is considered by many to be the founder of modern
technical drawing. Monge’s thoughts on the subject, Geometrie Descriptive (Descriptive Geometry),
published around 1799 became the basis for the first university courses.
The first English-language text on technical drawing, Treatise on Descriptive Geometry, was published in
1821 by Claude Crozet, a professor at the United States Military Academy.
© Technical Drawing 101 with AutoCAD All Rights Reserved
Smith, Ramirez and Schmidt
Chapter 2.
Part 1- The Language and Terminology
of Technical Drawing
Chapter Objectives - at the completion of this chapter students will be able to:
•Define the terminology used to describe the geometry of multiview drawings
•Describe points, lines, angles
•Describe polygons
•Describe 3D objects
•Describe projection planes
•Describe normal, inclined and oblique surfaces
•Describe line types
•Describe line weights
•Interpret the multiviews of graphic primitives
•Describe orthographic projection including the miter line technique
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Points, Planes, and Lines
Points
A point is an exact “location” in space that is defined by coordinates that are located relative to a known origin point.
Points are often represented in technical drawings by a visible “dot”, and while the dot representing a point is visible, the point has no
dimensional size.
Locating Points in Two Dimensional (2D) Coordinate Systems
In a two dimensional (2D) coordinate system, points are defined on a 2D flat surface that represents a plane. The coordinates of the
point are located by measuring from two perpendicular lines that represent the X (horizontal) and Y (vertical) axes. The intersection
where the X and Y axes meet is called the origin. In technical drawings, the X and Y axes represent a 2D area referred to as the “XY
plane”.
In the example below, the origin point’s value would be stated as “zero comma zero”, or (0,0), which means the location of the origin
is zero units (0) on the X axis and zero units (0) on the Y axis. A point, represented by a green dot, is located at coordinate 2,3. This
means that the point’s location is 2 units to the right of the origin on the X axis and 3 units above the origin on the Y axis.
Point located
at 2,3
Note: Coordinates that are
defined relative to a 0,0
origin are also referred to as
absolute coordinates.
Origin (0,0)
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In the example below, two points (in red) are defined on the XY plane at coordinates 1,2 and 4,3 respectively.
Origin Point (0,0)
Points that lie on the same plane are referred to as coplanar.
Points that share the same location are referred to as coincident.
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Negative Values in Two Dimensional (2D) Coordinate Systems
Points that are located below the X axis, or to the left of the Y axis, are described with negative coordinate values (a minus sign
precedes the coordinate).
In the example below, two points are defined at coordinates -3,1 and -1.5,-2.5 respectively.
Origin Point (0,0)
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Three Dimensional (3D) Coordinate Systems
In a three dimensional (3D) coordinate system, a Z axis is added to the X and Y axes. Using this system, points can be located relative
to the origin along the X, Y and Z axes. The Z axis represents the height of the point above or below the X,Y plane (see figure below).
For example, a 3D coordinate might be defined with the coordinates 1,1,1. This coordinate would lie one unit to the right of the origin
along the X axis, one unit from the origin along the Y axis, and one unit above the X,Y plane.
Origin Point (0,0,0)
of a 3D coordinate
system
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Lines
To a mathematician, a line is a set of continuous points that extend indefinitely in either direction.
In technical drawing terminology, a line is a segment defined by two endpoints. The endpoints are defined with coordinates.
Points that lie on the same line are referred to as collinear.
Noncollinear points do not lie on the same line.
In the example below, a red line begins at a start point located at coordinate 2,2 and
ends at a point located at coordinate 8,7 (relative to the origin). These point are
collinear.
A point located exactly halfway between the start and end points would be the line’s
midpoint.
Parallel Lines
Parallel lines run side by side at a uniform
distance and never intersect, even if
extended.
Two or more planes can be parallel relative
to each other. Lines can be parallel to
planes.
Spline
A smooth curve that passes through, or near,
specified points.
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Angles
Angle
An angle is formed when two, noncollinear lines have the same endpoint. The angle at right is formed by
sides BA and BC. The angle formed by these lines is referred to as angle ABC.
Vertex
In 2D space, the common point where two lines meet is called a vertex. The plural of vertex is vertices.
In the example at right, angle ABC’s vertex is point B and the its sides are lines BA and BC.
Note: When specifying an angle using letters or numbers, the vertex should be the middle letter in the series.
Note: The point where two lines cross is
referred to as an intersection - as
opposed to a vertex.
In 3D objects, a vertex is where the object’s edges
meet.
In the object at right, all of the vertices have been
assigned a number.
This object has a total of 17 vertices.
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Types of Angles
Right Angle
Acute Angle
Obtuse Angle
The angle between the sides
measures exactly 90 degrees.
The angle between the sides
measures less than 90
degrees.
The angle between the sides
measures greater than 90 degrees
but less than 180 degrees.
Perpendicularity
When two lines meet to form a right angle,
they are perpendicular. In the example
above, line BA is perpendicular to line BC.
Planes that meet at right angles to
each other are considered to be
perpendicular (see example at right),
Lines can also be perpendicular to
planes.
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Types of Angles
Complementary Angles
If two angles have a total measurement of 90 degrees
they are complementary angles.
Supplementary Angles
If two angles have a total measurement of 180 degrees
they are supplementary angles.
Opposite Angles
Adjacent Angles
When two lines cross, they form 4 angles. The
opposite angles have the same measure.
Where two lines cross, angles that share a common
side and common vertex, are called adjacent angles.
The sum of any two adjacent angle equals 180
degrees.
Therefore: Angle A = Angle B and Angle C = Angle D
Therefore, Angles A + C = 180 degrees and Angle C
+ B = 180 degrees, Angle B + D = 180 degrees and
Angle D + A = 180 degrees.
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Circles
Tangent
Circles
When a line touches a circle at only one point.
A circle can be defined by its center point and
either a diameter or radius (diameter/2)
Tangency Point
Diameter Symbol
Radius
Center Point
Two circles that touch at
only one point are tangent.
Flat surfaces can also be
tangent to curved surfaces.
Concentricity
When two or more circles share a common center
point they are concentric.
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Eccentricity
When two or more circles do not share a common
center point they are eccentric.
Polygons
Polygons are multi-sided, 2D figures composed of straight line segments. The polygon’s start and end points meet at the same point which creates a
“closed” figure. Polygons are classified by the number of sides they contain.
Triangles - Three sided polygons.
Quadrilaterals - Four sided polygons.
Right
Triangle
Rectangle
Square
One right angle.
Equilateral
Three equal angles.
Scalene
No equal angles.
Hexagons - Six sided polygons.
Hexagon constructed by
inscribing it within a circle.
Hexagon constructed by
circumscribing it around a circle.
Pentagons - Five sided polygons.
Heptagon - Seven sided polygons.
Octagons - Eight sided polygons.
Nonagons - Nine sided polygons.
Decagons - Ten sided polygons.
Dodecagons - Twelve sided polygons.
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Cylinders
Cylinders
A cylinder is a 3D object that is defined by its
center axis, diameter or radius (diameter/2), and
height.
Flat surfaces can also be
tangent to curved surfaces.
Plane tangent to a cylinder
Center Axis
Coaxial
When two or more
cylinders are aligned
along the same center
axis they are coaxial.
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Center planes meeting
along center axis.
Today’s Lesson-Part 2:
An Introduction to Multiview Drawing
Multiview drawing is a technique used by drafters and designers to depict a three-dimensional object as a
group of related two-dimensional “views” that show the size and shape of the object.
For example, Figure 2.1 provides a three-dimensional (3D) image of a school bus, and while a 3D view of
the bus is very helpful in visualizing its overall shape, it doesn’t show the viewer all of the sides of the
bus, or the true length, width, or height of the bus.
Figure 2.1
A three dimensional image of a school bus.
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A better way to fully describe the bus graphically would be to create a multiview drawing as shown in
Figure 2.2. The multiview drawing of the bus is represented by six views, the front, top, sides, back and
bottom. These views represent the six “regular” views of the bus.
In creating the multi-view drawing of the bus, the front, or principal, view was drawn first. The bus was
then “rotated” at 90 degree intervals relative to the front view to create the top, bottom, right and left side
views. The left side view was then rotated 90 degrees to the left to create the rear view.
Some form of multiview drawing is employed by every discipline of engineering or architecture, so in
order to be successful in their careers, drafters and designers must master the techniques involved in
creating and interpreting multiview drawings.
Top View
Figure 2.2
The multiviews of the bus.
Rear View
Left View
Front View
Right View
Bottom View
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While a total of six views are possible using the
multiview drawing technique, drafters draw only
the views necessary to describe an object.
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Multiview Projection Planes
If a house is placed inside a glass box as in Figure
2.3, the transparent sides of the box would create
projection planes (also known as viewing planes)
that the features of the house can be “projected”
onto.
Figure 2.6
The view through the horizontal
projection plane shows the top view
or roof plan. This view reveals the
width and depth of the house.
Likewise, in Figures 2.5 and 2.6, the
right side and top views of the house are
shown as they would appear if projected
onto the profile projection and horizontal
projection planes respectively.
Figure 2.4
The view through the frontal
projection plane shows the
front view of the house. This
view furnishes the width and
height of the house.
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Viewer’s Line
of Sight
In Figure 2.4 the front view of the house
is shown as it would appear if projected
onto a frontal projection plane that has
been placed between the viewer and the
object.
Figure 2.3
Figure 2.5
The view through the profile
projection plane reveals the right
side view of the house. This view
furnishes the depth and height of
the house.
In Figure 2.7, notice how a feature like the peak of the roof in the front view, is exactly in line with the top of the roof in
both the left and right views. Observe how the features of the chimney are depicted in each of the views.
The planes representing the roof in the right, left, and top views appear as rectangles in the multiviews, but by
studying them in relation to the front view, you will see that they actually represent the sloping planes of the roof. Since
the planes of the roof, as projected through the top and side projection planes are sloping, they are not drawn actual,
or true size. In technical drawing, this phenomenon is referred to as “foreshortening”.
Figure 2.7 The “Elevations” of a House as
They would Appear in a Multiview Drawing.
TOP VIEW
LEFT VIEW
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FRONT VIEW
RIGHT VIEW
First Class Activity
Creating 2D Multiviews of a 3D Object
In this activity your instructor will furnish you with a
die. Orient the die so that the front and top views
match the ones show at right. Starting from this
orientation, rotate the die as needed to find the
missing views (right, left, back and bottom). Fill in the
circles to match the corresponding view. Repeat this
process to complete each of the other sheets. Return
the die to your instructor following this activity.
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Dice 1 Solution
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Dice 2:
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Dice 3:
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Dice 4:
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Dice 5:
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Dice 3 Solution
Dice 2 Solution
2
3
Dice 5 Solution
Dice 4 Solution
4
5
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Home Work Assignment: Read all of Chapter 1 and up through the Chapter Summary of Chapter 2.
Unit 2.
Multiview Drawing
Chapter Objectives
•Explain what multiview drawings are and their importance to the field of technical
drawing.
•Explain how views are chosen and aligned in a multiview drawing.
•Visualize and interpret the multiviews of an object.
•Describe the line types and line weights used in technical drawings as defined by
the ASME Y14.2M standard.
•Explain the difference between drawings created with First Angle and Third Angle
projection techniques.
•Use a miter line to project information between top and side views.
•Create multiview sketches of objects including the correct placement and
depiction of visible, hidden and center lines.
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