Class 7 - MultiView Drawings

8/8/2019 Class 7 - MultiView Drawings

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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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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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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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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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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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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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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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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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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

Class 7 - MultiView Drawings

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