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Engineering Graphics, Class 5Multi-View Drawings
Mohammad I. KilaniMechanical Engineering Department
University of Jordan
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Views of an Object
A pictorial drawing shows an object asit appears to the observer, but not inits true lengths
Such a picture cannot describe theobject fully, no matter which directionit is viewed from, because it does notshow the exact shapes and sizes of theseveral parts.
In industry, a complete and cleardescription of the shape and size of anobject to be made is necessary
Therefore, a number of viewssystematically arranged, are used.
This system of view is called multi-view projection
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Views of an Object
Each view provides certain definite information if the view isfrom a direction perpendicular to a principle face or side ofthe object.
If the observer is looking perpendicularly toward the front
face of the object, he/she obtains a true view of the shapeand size of that side, the same may be said about the topand side views
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Views of an Object
The front view in the figure below shows only the height andwidth of the object and not the depth
Any one view of a three-dimensional object shows only twodimensions, the third dimension is found in an adjacent view
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Views of an Object
The three principledimensions of an object are
width, height and depth
These fixed terms are usedfor dimensions taken in thesedirections, regardless of the
shape of the object
The terms length & thicknessare not used because theycannot be applied in all
cases.
In a front view of an object,only the width and heightdimensions appear.
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Revolving and Object
Other views can be obtainedby revolving the object
Hold the object in the frontview position
Top view: revolve the objectto bring the top of the objectup and toward you
Right-side view: revolve theobject to bring the right sidetoward you
View of any other sides: turnthe object to bring thoseside toward you
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Regular Views of an Object
The regular views of anobject are its top, front, andright-side views
These views are arrangedclose to each other as shownin (d)
These three view are themost frequently used
Spacing between views is amatter of appearance
They should be spaced wellapart, yet close enough toappear related to each other
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Regular Views of an Object
The space between the frontand top views may or maynot be equal to the spacebetween the front and sideviews.
If dimensions are to beadded to the views,
adequate space for them willhave to be left betweenviews
Hidden features can beclearly shown by means ofhidden lines
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Regular Views of an Object
In the front view,surface 7-8-9-10appears in its truesize. This surfaceappears as a visibleline 5-6 in the topview and as a hiddenline 15-16 in the sideview
In the front view,hole A, appears as acircle, This holeshows as hidden
lines 1-4, and 2-3 inthe top view, and 11-12 and 13-14 in theside view
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The Six Views of an Object
Any object can be viewed from six mutually perpendicular directions. These sixviews may be drawn if necessary
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The Six Views of an Object
These views are always arranged as shown which is the American National StandardArrangement. The Top, front, and bottom views align vertically, while the rear, left-side, front and right-side views align horizontally.
Drawing a view out of place is generally regarded as one of the worst possiblemistakesin drawing
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The Six Views of an Object
Height is shown in the rear, left-side, front, and right-side views. Width is shown in the rear, top, front, and bottom views. Depth is shown in the four views that surround the front view
In the four views that surround the front view, the front of the object faces towardsthe front view.
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The Six Views of an Object
In the four views that surround the front view, the front of the object faces towardsthe front view. i.e. if the front view in the figure is imagined to be the object itself,the right-side view is obtained by looking toward the right side of the front view.
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The Six Views of an Object
Any of the six views can be obtained either by rotating the object with respect to theobserver or by rotating the observer with respect to the object.
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The Six Views of an Object
In architectural drawings plan is used for the top view, elevation for all viewsshowing the height of the building
Height is shown in the rear, left-side, front, and right-side views.
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The Six Views of an Object
In, general, the front view shows the object in its operating position, particularlyof familiar object, like the house example
In most cases this is not important, and the drafter may assume the object to bein any convenient position.
In the figure below the front view is the side, not the front of the automobile.
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Necessary Views
Necessary views, are the minimum number of views needed for a clear andcomplete shape description of the object
In selecting views, the drafter should choose those that best show essential
contours or shapes and have the least number of hidden lines
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Necessary Views
Three features of the object below need to be shown on the drawing: Rounded top and holeseen from the front Rectangular notch and round cornersseen from the top Right angle with filleted corner seen from the side
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Necessary Views
Both the front and rear views show the true shapes of the hole and the round top.But, the front view is preferred because it has no hidden lines, so the rear view iscrossed out
Both the top and bottom views show the rectangular notch and rounded corner,But, the top view is preferred because it has fewer hidden lines.
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Necessary Views
Both the right-side and left-side views show the right angle with the filletedcorner. In this example the side views are identical, except reversed. In suchinstance, it is customary to choose the right-side view, so the necessary vieware the three remaining views.
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Two-View Drawings
Often only two views are needed toclearly describe the shape of an object.
In figures (a) and (c), the right side viewshows no significant contours of theobject and is crossed out
In figure (b) the top and front views areidentical, so the top view is eliminated
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Two-View Drawings
If an object requires only two views and thetop and bottom views are equally descriptive,the top view is customarily chosen.
If an object requires only two views and theleft-side and the right-side views are equallydescriptive, the right-side view is customarilychosen.
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Two-View Drawings
If only twoviews arenecessary and
the top viewand the right-side view areequallydescriptive, thecombinationchosen is theone that spacesbest on thepaper.
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One-View Drawings
A single view supplemented by a note or lettered symbols is sufficient todescribe clearly the shape of a relatively simple object
In the figure, one view of the shim plus a note indicating the thickness as 0.25mm is sufficient.
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One-View Drawings
In the figure the left end is 65 mm square, the next portion is 49.22 mm diameter, the next is 31.75 mm diameter, and the portion with the thread is 31.75 mm diameter, as indicated in the note
Nearly all shafts, bolts, screws, and similar parts should be represented bysingle views in this manner
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Hidden Lines
Hidden line should join a visible line except when it causes the visible line toextend too far (a & g), so, leave a gap whenever a hidden line is acontinuation of a visible line
Hidden lines should intersect to form L and T corners (b)
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Hidden Lines
A hidden line should jump a visible line when possible (c) Parallel hidden lines should be drawn so that the dashes are staggered (d), When two or three hidden lines meet at a point, the dashes should join (e-f)
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Hidden Lines
A Poorly drawn hidden lines can easily spoil a drawing
Dashes should be about 5 mm long and spaced about 1mm apart, by eye
Accent the beginning and end of each dash by pressingdown on the pencil, whether drawn freehand ormechanically
Hidden lines should be used when necessary to make the
drawing clear
Hidden lines not needed for clarity should be omitted soas not to clutter the drawing and also to save time
The beginner, should be cautious about leaving out
hidden lines until experience shows when they can besafely omitted
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Center Lines
Center line are used to indicate axes of symmetrical objects or features, bolt circles,and paths of motion.
The small dashes should cross at the intersection of center line Center lines should extend about 8 mm outside the feature for which they are drawn
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Center Lines
The long dashes may vary from 20 to 40 mm or more in length, depending on thesize of the drawing.
The short dashes should be about 5 mm long, with spaces about 2 mm Center lines should always starts and ends with long dashes
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Center Lines
Short center lines specially for small holes, may be made solid (e) Always leave a gap when a center line formulate a continuation of a
hidden or a visible line Center lines should be thin enough to contrast well with the visible and
hidden lines, but dark enough to reproduce well
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Alignment of Views
Drawings arranged in accordance with the American National Standard must satisfy thefollowing alignment conditions:
All views line up with the front view
The top view must be directly above the front view
The right-side view must be directly to the right of the front view
Never draw the views in reversed positions, with the bottom over the front view or the right-
side to the left of the front view, even if the views line up with the front view
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Alignment of Views
Never draw the views in reversed positions, with the bottom over the front view or the right-side to the left of the front view, even if the views line up with the front view
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Meanings of Lines
A visible or a hiddenline has three possiblemeanings:
Intersection oftwo surfaces
Edge view of asurface
Contour view of acurved surface
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Precedence of Lines
Visible lines, hiddenlines, and centerlines often coincideon a drawing
A visible line alwaystakes precedenceover a center line ora hidden line
A hidden line takeprecedence over acenter line