Chapter 4

OrthographicWriting

Contents

Orthographic writing

Overall steps1. Select the necessary views2. Layout the selected views on a drawing sheet. 3. Complete each selected views.4. Complete the dimensions and notes. 451521526425~40FrontTopChoose a drawing scale(say 1:1)FrontTop

Take first : C = A3A +108+58=400A= 234/3=78Then: A = 80, C= 234-160=74

Repeat similar step for B and D

First row: 20 THRU

Sketch the layout if you need to draw 3 views orthographic projection : front, top, and right side views of the following pictorial figures. Scale 2 : 1.

View selection procedures1. Orient the object to the best position relative to a glass box. 2. Select the front view.3. Select adjacent views.

Suggestions : Orient the object1. The object should be placed in its natural position.NO !2. The orthographic views should represent the true size and true shape of an object (as much as possible).GOOD

Suggestions : Select the front view1. The longest dimension of an object should be presented as a width (in a front view).InappropriateFirst choiceGoodSecond choiceUse more space

Inappropriate2. The adjacent views project from the selected front view should be appeared in a natural position.Suggestions : Select the front view

3. It has the fewest number of hidden lines.GoodInappropriateSuggestions : Select the front view

Suggestions : Select an adjacent viewInappropriateInappropriate1. Choose the view that has the fewest number of hidden lines.

2. Choose the minimum number of views that can represent the major features of the object.NecessaryNecessaryHoles information is placed on a separated view.Suggestions : Select an adjacent viewAll information is placedon a single view.

3. Choose the views that are suitable to a drawing sheet.GoodSuggestions : Select an adjacent viewPoorNot enough spacefor dimensioning.GoodChoose another adjacent view.Change orientation of theselected views.

SummaryView selection has 3 stepsIn practice, drafter should consider all recommendationssimultaneously before start to draw.Orientthe objectSelectfront viewSelectadjacent view

Additional examples on a view selection

NotesIn a usual case, three views orthographic drawingis selected to describes an objects information.However, a necessary view may be less or more than three views.Later chapter

Object that requires only one-viewFlat (thin) part having a uniform thickness such as a gasket, sheet metal etc.Adjacent views provide only aparts thickness !1 ThickCylindrical-shaped part.Example

Repeat !Infer from CLObject that requires only one-viewExampleExampleFlat (thin) part having a uniform thickness such as a gasket, sheet metal etc.Cylindrical-shaped part.

Identical adjacent view exists.Repeat !Object that requires only two-viewThe 3rd view has no significant contours of the object.(provides no additional information)Example

Object that requires only two-viewIdentical view exists.Example 1The 3rd view has no significant contours of the object.(provides no additional information)

Object that requires only two-viewIdentical view exists.Example 2The 3rd view has no significant contours of the object.(provides no additional information)

Class activity : View selection213465Select a necessary view ?

Class activity : View selectionSelect a necessary view ?213465

Class activity : View selection213465Select a necessary view ?

Alignmentof views

Projection systems1. First angle system2. Third angle systemFirstquadrantThirdquadrant- European countries - ISO standard- Canada, USA, Japan, ThailandTransparentplanesOpaqueplanes

1st angle system(Opaque planes)3rd angle system(transparent planes/glass box)Orthographic views

FoldinglineFoldinglineFoldinglineFoldingline1st angle system3rd angle systemOrthographic views

1st angle system3rd angle systemFront ViewFront ViewRight Side ViewRight Side ViewTop ViewTop ViewViews arrangement

Projection symbols1st angle system3rd angle systemd1.7d2.2d

CLASS ASSIGNMENT-3 :

Neatly draw the front, top, and right side views of the following pictorial figures. Scale 2 : 1.