TA 101: Technical Arts 2015-16 II Dr. Prishati Raychowdhury Department of Civil Engineering IIT Kanpur Office: FB 336; Phone: 6692 E-mail: prishati@iitk.ac.in

Orthographic Projections with Dimensions Lecture 5 Orthographic Projections with Dimensions

Review (a) (b) Object in FIRST quadrant Object in THIRD quadrant

Review (a) (b) Third Angle Projection First Angle Projection RIGHT VIEW FRONT VIEW TOP VIEW Third Angle Projection First Angle Projection

Example: Orthographic Projection

Why Projection Method is Important F 1 1a 2 2a 3 3a 5 4a 5a 6 6a 7 7a 8a 9a 10a 1a 2a 3a 4a 5a 6a 7a 8a 9a 10a cT bT dT aT eT hT fT gT 450 2 2a 10 10a aR bR hR cR gR fR dR eR

Terminology Convention/Terminology for Civil Engineering /Infrastructure related drawings: Top view: Plan View (or Plan) Front view: Front Elevation Side/Profile view: Side Elevation

A typical architectural drawing

Dimensioning To describe various features of an object Size (width, height, depth etc.) Position of features (e.g. holes) with respect to edges, other holes etc.

Purpose of Dimensioning To make the drawing easier to understand by the manufacturer or builder Make the drawing simpler, cleaner and more legible Simpler to draw, redraw or reproduce Appropriate number of dimensions Not too many Not too few

Dimensioning Four aspects of dimensioning Unit? Lines Symbols Figures Notes R 250 Ø 254, 200 deep 320 95 Unit? 400 thick 95 190 All dimensions in m/cm/mm/FT/inch

Dimensioning How many dimensions per view? The object should be able to be manufactured or built Most objects: 3 dimensions Cylinders: 2 dimensions Sphere: 1 dimension

Dimensioning Basics Dimension line should not touch the object Front view 95 Letter size: 6 mm Pencil: H Units not written Red: Extension line Blue: Dimension line Gap between extension line and object: 1-1.5 mm All dimensions in mm

Dimensioning Basics Which view to dimension? Show dimensions in the view that shows the most relevant features R 250 Ø 254 320 95 95 140 190

Dimensioning Basics A dimension should not be repeated [e.g. if a dimension is given in the front view, it is not shown again in another view] A D E C B D E

Dimensioning Basics Place dimensions outside the view, as far as possible R 250 R 250 50 50 25 25 20 20 75 75

Dimensioning Basics Take dimensions out from visible outlines than from hidden lines

Dimensioning Basics Dimensions should be unidirectional as much as possible

Dimensioning Basics Give dimension from Baseline / finished surface / centerline of a hole

Dimensioning Basics Give dimension from Baseline /finished surface /centerline of a hole Except when centerline (or axis of symmetry) passes through center of hole Ø 150 2 holes, Ø 50 R 50 R 100 250 500 100 80 30

Types of Dimensions Two types Size Location D B B C D E A F

Types of Dimensions Two types Size Location P A B C

Dimensioning a Length Depending on available space Half Arrows Arrows 2500 250 80 40 Dots 800 160 Lines 500 90 260 190 50

Placing of Dimensioning Only two sides are preferable Dimensions read from the bottom and from the right

Placing of Dimensioning Arrow and text A A Dimensions read from the bottom and from the right C C B B D D E E

Placing of Dimensioning Orientation of dimensioning text A A Dimensions read from the bottom and from the right C C B B D D E E Unidirectional Aligned

Placing of Dimensioning Zones for allowed alignments Leader lines, Arrows, text Avoid 30-45º 150 120 90 Avoid

Placing of Dimensioning Narrow spaces A A C Dimensions read from the bottom and from the right C B B D D E E Unidirectional Aligned

Arrangement of Dimensions Two basic styles Parallel Dimensions Chain Dimensions

Arrangement of Dimensions Combined style

Dimensioning Diameters Most appropriate view Ensure clarity Precede with “” to distinguish from length

Dimensioning Radii Arcs of circles Precede with “R” to distinguish from length R 100 260 R 30 250

Dimensioning Dimensioning in limited spaces 6 3 22 19 4.8 5 22 ø26 18 21.5 12 300’ 45” Dimensioning in limited spaces

Example 1: Arrangement of Dimensions

Example 2: Over-dimensioning Do not provide too many dimensions

Example 3: Positioning Choose appropriate location J H I Ø G Ø G R 20 F B A

First Angle Projection

? VIEW FRONT VIEW TOP VIEW SCALE 1:2

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