# TECHNICAL SKETCHING & DRAWING

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TECHNICAL SKETCHING& DRAWING, engineering drawing, Distinguish the type of technical drawing existed in engineering graphics – isometric, oblique &orthographicProduce manual 2D drawingsProduce orthographic and sectional view drawingmanually, given an isometric drawing.

### Text of TECHNICAL SKETCHING & DRAWING

• CHAPTER 2 part b

TECHNICAL SKETCHING & DRAWING

CCB 1052

• CCB 1052

Learning OutcomesBy 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 Viewsa) 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 projectionStep 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 objectStep 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 objectOblique drawing is drawn normally as follows:

2. Oblique views - a method of displaying an object or shapein 3 dimensions

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Orthographic /Multiview ProjectionOrthographic views are 2-D views of 3-D objects. The top, front and right-side views are adequate to completely define and objects 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 ProjectionThe 6 Principal Views

6 mutually perpendicular views that are produced by 6 mutuallyperpendicular 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 viewsSectional 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. equalspacing between the 2 views & between each view & the edge of paper.-Normally, if the front & right side views are used, the paper is orientedso that the long dimension run horizontally.-If the front & top views are used, the long dimension of the paper runsvertically.

Remember: The top view always is aligned with & placed above the front view, and the right side view always is aligned with and placedto the right of the front view.

Guidelines of creating two-view sketch

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Creating a three-view sketchTake-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, useconstruction lines to project the width dimension from front view to topview. Also project the height dimension from the front view to the rightside view.Step 2: Lightly block in the major features seen in each view e.g drilledholes & angled edge.Step 3: Use construction lines to project the location or size of a featurefrom one view to another. Remember each view always shares 1-D withthe adjourning view. Mitter line is drawn at a 45 degree angle & is usedas a point of intersection for lines coming to & from the right side & topviews.Step 4: Finish adding the rest of the final lines. Be careful to do allhidden 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 viewTake-home practice

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Individual assignment 1

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