Chapter 10 Projection of solids

ENGINEERING GRAPHICS(TA C111)

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Classification of solids

Projection of solids (in simple positions)

Axis perpendicular to one reference plane

Transfer of points from one view to the other view

Axis inclined to one reference plane and parallel to the other

Projections drawn in two stages:

STAGE I: Solid is assumed to be in simple position i.e. its axis perpendicular to one of the planes

STAGE II: Alteration of axis orientation i.e. the orientation of the axis is altered as required and the other view projected from it

The 1The 1stst stage should be such that we should be stage should be such that we should be able to draw the able to draw the true viewstrue views from the top and from the top and

front easilyfront easily

Axis perpendicular w.r.t. which plane??

If the axis is inclined to the ground i.e the H.P.It is assumed to be perpendicular to the H.P. in STAGE I

If the axis is inclined to the V.P. It is assumed to be perpendicular to the V.P. in STAGE I

While drawing the TS of the base (STAGE I) consider the given rest condition in the problem. If it is resting on:

Base-edge: Draw that base-edge perpendicular to x-y line.

Base-corner: Draw the line joining the base-corner and center of base parallel to XY line.

Slant face (PYRAMID)/rectangular face (PRISM): Draw the base-edge of that slant face perpendicular to x-y line.

Slant/vertical edge: Draw the line joining the base-corner of that slant/vertical edge and center of base parallel to x-y line.

Orientations of the base (rest condition)

Visibility of points

The highest parts of the object are visible in the view from TOP. The view from the front gives a clue regarding this.

The front faces, the front edges and the front corners nearest to the observer are visible in the view from front. These can also be determined from the view from TOP.

Example:

When the object is resting on BASE EDGE

A hexagonal pyramid, A hexagonal pyramid, base 100 mm and height base 100 mm and height 175 mm, has an edge of 175 mm, has an edge of its base on the ground. its base on the ground. Its axis is inclined at 30Its axis is inclined at 30°°

to the ground and to the ground and parallel to the V.P. Draw parallel to the V.P. Draw

its projections.its projections.

11

22

44

33

66

55

View OK?

Example:

When the object is resting on BASE EDGE

A hexagonal pyramid, A hexagonal pyramid, base 100 mm and height base 100 mm and height 175 mm, has an edge of 175 mm, has an edge of its base on the ground. its base on the ground. Its axis is inclined at 30Its axis is inclined at 30°°

to the ground and to the ground and parallel to the V.P. Draw parallel to the V.P. Draw

its projections.its projections.

Example:

When the object is resting on a BASE CORNER

Draw the projections of a Draw the projections of a cube of 100 mm long cube of 100 mm long edges resting on the edges resting on the ground on one of its ground on one of its corners with a body corners with a body

diagonal passing through diagonal passing through that corner perpendicular that corner perpendicular

to the H.P.to the H.P.

b b

Example:

When the object is resting on SLANT FACE/RECTANGULAR FACE

Draw the projections Draw the projections of a pentagonal of a pentagonal

prism, base edge prism, base edge 100 mm and height 100 mm and height 175 mm, resting on 175 mm, resting on

one of its one of its rectangular faces on rectangular faces on the ground, with the the ground, with the axis inclined at 45axis inclined at 45°°

to the V.P.to the V.P.

Example:

When the object is resting on SLANT FACE/RECTANGULAR FACE

Draw the projections Draw the projections of a pentagonal of a pentagonal

prism, base edge prism, base edge 100 mm and height 100 mm and height 175 mm, resting on 175 mm, resting on

one of its one of its rectangular faces on rectangular faces on the ground, with the the ground, with the axis inclined at 45axis inclined at 45°°

to the V.P.to the V.P.

Example:

When the object is resting on SLANT/ VERTICAL EDGE

A hexagonal A hexagonal pyramid, base 100 pyramid, base 100 mm and height 175 mm and height 175 mm, has one of its mm, has one of its slant edges on the slant edges on the ground. A plane ground. A plane containing that containing that

edge and the axis edge and the axis is perpendicular to is perpendicular to

the ground and the ground and also perpendicular also perpendicular

to VP. Draw its to VP. Draw its projections when projections when the apex is nearer the apex is nearer to the observer.to the observer.

Example:

Projections of a cylinder

Example:

Projections of a cone