Engineering Graphics 2018-19-I Lecture 4 TA101A Engineering Graphics 2018-19-I By Dr. Mukesh Sharma Professor DEPARTMENT OF CIVIL ENGINEERING INDIAN INSTITUTE OF TECHNOLOGY KANPUR KANPUR-208016, INDIA

Class on Saturday 11.8. 2018 ?

Quadrant 1 and Quadrant 3 are Used for Orthographic Projections Above Above Front 2nd 1st Quad 3rd Quad 4th Front Viewing Direction is same irrespective of quadrant where object is kept Quadrant 1 and Quadrant 3 are Used for Orthographic Projections In whatever Quadrant the object is in, viewing directions are same In what quadrant, so far, we have been keeping the object in?

Revisit 3rd Angle Projection Scheme This is Profile Plane Here too Observer – Plane - Object RECAP of Concept Object - Plane - Observer

3rd Angle Projection Scheme contd.. See the positions of Front, top, RS, LS Views FOR LSV ALSO IT IS TRUE Object - Plane - Observer

1st Angle Projection Scheme RS LS Front Top See the positions of Front, top, RS, LS Views Examine how different these are from 3rd angle projection And why? Hinge Plane - Object - Observer

Concept In 3rd angle Projection Observer – Plane - Object Position wrt Front view; top view is above, R-S View on right and L-S view on left In 1st angle projection Observer – Object - Plane top view is below, R-S View on left and L-S view on right

Theory of Dimensioning -Techniques and Conventions Object is made of several parts – Need Position (P) Size (S) Each feature is dimensioned once For each feature, dimension positioned where its shape shows No Redundancy

Avoid giving any dimensions inside the drawing. Extension Lines Dimension Lines Arc and Circular Features S S S P S S(RAD.) S S: Size P: Position S P P P S S Drill, 2 holes Arrow Dimensions ALL DIMENSIONS IN MM (Near Title Block) x 3x Avoid giving any dimensions inside the drawing. No two dimension lines cross each other. Center line can be used as extension line. x=1mm usually

Extension line Arrowhead Dimension line Leader 2 Holes, ø12 Note

45 60 ø40 20 40 ø20 ø60 A B C D Ø20 Drill

Unidirectional System Aligned System values read from bottom only (Preferred when?) values read from bottom and Right side

16 60 10 30 50 Continuous or Chain Dimensioning 20 Progressive or Parallel Dimensioning - From Common Base (Preferred)

Areas to avoid – Place them so to read conveniently 126 450 100 80 Avoid Areas to avoid – Place them so to read conveniently

CORRECT INCORRECT

Omit unnecessary dimensions.

Dimensioning of arcs Single arrow, inclined, show where true shape (aligned and unidirectional)

Equally spaced holes.

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

} Today’s Quiz Drawn in Title Block to indicate type of projection. Identify the angle of projection } Drawn in Title Block to indicate type of projection. Third angle First angle Third angle