Download - TECHNICAL SKETCHING & DRAWING
CHAPTER 2 part b
TECHNICAL SKETCHING
& DRAWING
CCB 1052
CCB 1052
Learning Outcomes
By the end of this lesson, student should be able to
Distinguish the type of technical drawing existed in engineering graphics – isometric, oblique & orthographic
Produce manual 2D drawings
Produce orthographic and sectional view drawing manually, given an isometric drawing.
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Lines Alphabet of lines: (observe
thickness & darkness of lines)
Continuous lines used to show edges directly visible from a particular angle
Short dashed lines that may be used to represent edges that are not directly visible
Thin lines in a pattern used to indicate surfaces in section views resulting form cutting (cross-hatching)
Long & short dashed lines to represent the axes of circular features
(Object ) 0.6 mm
0.3 mm
0.3 mm
0.3 mm
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Lines
Thick, long & double short dashed lines used to define sections for sections view
0.3mm
0.6 mm
0.6 mm
0.3 mm
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Lines
Long & double short dashed thin lines to represent a feature or component that is not part of assembly
0.3 mm
0.3 mm
0.6 mm
0.3 mm
Borderline of objects drawn
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Projection and Views
a) Pictorial Projection
•Isometric
•Oblique
b) Multiviews (Orthographics)
Projection
c) Section Views
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A) Pictorial Projection
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Pictorial projection
Is a 3-D drawing/views that are based on isometric
axis, i.e., lines that are 120o apart. The modified
version can also be drawn with a vertical line and two
30o lines from horizontal plane
Figure 4-13
30o30o
1. Isometric views
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Pictorial projection
Isometric lines – lines that run parallel to any of the
isometric axes.
Nonisometric line – Any line that does not run parallel
to an isometric axis.
1. Isometric views
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Pictorial projection
Step 1 - Begin with defining an isometric axis, which is made of 3 lines, one
vertical and two drawn at 30 degrees from horizontal. These 3 lines of the
isometric axis represent the 3 primary dimensions of the object – width, height
& depth
Step 2 – Extend the isometric axes & label all corners
Step 3 – Sketch front face of the object
Step 4 – Sketch top and side faces
Step 5 – Lay out all construction lines
Step 6 – Estimate the distances to create the angled surface of the block.
Step 7 – Darken all visible lines to complete the isometric sketch
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Pictorial projection
Isometric lines – lines that run parallel to any of the
isometric axes.
Nonisometric line – Any line that does not run parallel
to an isometric axis.
Basic steps to create an isometric sketch of an object
ovject
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Pictorial projection
A form of parallel projection in which the projectors are
parallel to each other but are not perpendicular to the
projection plane.
Angles of between 30 and 60 degrees are preferable
because they result in minimum distortion of the object
Oblique drawing is drawn normally as follows:
2. Oblique views - a method of displaying an object or shape
in 3 dimensions
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Orthographic /Multiview Projection
Orthographic views are 2-D views of 3-D objects.
The top, front and right-side views are adequate to
completely define and object’s shape. Parallel lines
of sight
Figure 5-1
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Orthographic/ Multiview ProjectionB) Multiviews (Orthographics) Projection
-is a parallel projection technique in which the plane of
projection(imaginary flat plane) is positioned between the
observer and the object & is perpendicular to the parallel line
of sight.
- Produce 2-D views from 3-D objects. The views are defined
according to the positions of the planes of projection with
respect to the object.
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Orthographic/ Multiview Projection
- Note: the Depth dimension cannot be presented since it is
perpendicular to the paper.
Single view/Front view
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Orthographic/ Multiview Projection
-Note: A top view of the object is created by projecting onto the
horizontal plane of projection.
- Height dimension cannot be seen.
Top view/Ariel view
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Orthographic/ Multiview Projection
- A right side view of the object is created by projecting onto
the profile plane of projection
-Note: the Width dimension cannot be presented since it is
perpendicular to the paper.
Right side view/Profile view
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Orthographic/ Multiview Projection
- For this object, 3 views are created: front, top & right side.
- The views are aligned so that common dimensions are
shared between views.
Multiview drawing of an object
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Orthographic/ Multiview Projection
The 6 Principal Views
6 mutually perpendicular views that are produced by 6 mutually
perpendicular planes of projection.
Imagine suspending an object in a glass box with major surfaces of
the object positioned so that they are parallel to the sides of the box.
The 6 sides of the box become projection planes showing the six
views.
The six principal views are front, top, left side, right side, bottom
and rear.
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Orthographic/ Multiview Projection
Unfolding the glass box to produce a six-view drawing
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Ortographic vs Pictorial projectionDifference between orthographic & oblique projection
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Orthographic and Isometric views
Figure 4-13
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The dashed lines indicate hidden features
Orthographic and Isometric views
Top
FrontRight
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C) Sectional views
Sectional views are used in technical drawing to reveal
internal surfaces.
The purpose is to complement orthographic views of
surfaces that appear as hidden lines in top, front and right
views.
A primary reason for creating section view is the
elimination of hidden lines, so that drawing can be
understood or visualized more easily.
Hatch lines are drawn on the surfaces that represent
where the cutting plane passed through solid material.
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Sectional views
Figure 6-1A
Pictorial projections
Orthographic
projection with
cutting plane A
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Sectional views
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Imaginary cutting plane that cuts through the object
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Summary
Types of drawing views:
* Oblique and Isometric Views
* Orthographic and Sectional Views
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Creating two-view sketch
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Take-home practice
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Centering a two-view sketchA two-view sketch is centered on a sheet of paper by equallydividing the areas between & around the views
Take-home practice
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-Occasionally, an object can be described completely using only 2 views
- If the front view is shown, the top & side views would be the same (no
point showing both).
-Scale & locate the views on the drawing so that there is approx. equal
spacing between the 2 views & between each view & the edge of paper.
-Normally, if the front & right side views are used, the paper is oriented
so that the long dimension run horizontally.
-If the front & top views are used, the long dimension of the paper runs
vertically.
Remember: The top view always is aligned with & placed above the
front view, and the right side view always is aligned with and placed
to the right of the front view.
Guidelines of creating two-view sketch
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Creating a three-view sketch
Take-home practice
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Step1 : Begin by blocking in the front, top & side views of the object,
using the overall width, height & depth. Sketch the front view first, use
construction lines to project the width dimension from front view to top
view. Also project the height dimension from the front view to the right
side view.
Step 2: Lightly block in the major features seen in each view e.g drilled
holes & angled edge.
Step 3: Use construction lines to project the location or size of a feature
from one view to another. Remember each view always shares 1-D with
the adjourning view. Mitter line is drawn at a 45 degree angle & is used
as a point of intersection for lines coming to & from the right side & top
views.
Step 4: Finish adding the rest of the final lines. Be careful to do all
hidden lines & center lines for the holes. Darken all final lines.
Guidelines of creating three-view sketch
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Imaginary cutting plane
Creating section view
Take-home practice
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Individual assignment 1
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