4. Basically, orthographic projection
means a 2-dimensional representation
of and 3-dimensional solid object. The
object is represented by projecting
lines from its edges such that the lines
are orthogonal to the projection plane.
5. Basically, there are 2 types of
orthographic projection. They are:
1) 1st angle projection
And
2)3rd angle projection
They are explained below.
7. The one and only difference between 1st
angle & 3rd angle projection is that only the
representation positions of plan (top view),
bottom view and side view.
In 1st angle projection, the front view is in
center, top view is below front view, bottom
view is above front view, RHSV(right hand
side view) is to the left of front view and
LHSV(left hand side view) is to the right of
front view.
12. SYMBOLS USED ON
ENGINEERING DRAWING SHEET
FIRST ANGLE METHOD
OF
ORTHOGRAPHIC
PROJECTIONS
THIRD ANGLE METHOD
OF
ORTHOGRAPHIC
PROJECTIONS
M/c. PARTS ARE NEVER ASSUMED IN SECOND
OR IN FOURTH QUADRANT, AS THE VIEWS MAY
OVERLAP ON ONE ANOTHER ABOVE XY OR
BELOW XY RESPECTIVELY.
13. Step by step procedure Suggested
to prepare Orthographic views
(First angle method) for The simple
component Shown pictorially in
figure
16. Figure shows the isometric
view of a vertical shaft support.
Draw its all the three views,
using first angle method of
projections.
Give the necessary dimensions
as per aligned system.
Exercise :-
20. Sectional view is used to indicate that when
the solid is cut from a particular plane, where
there is mass and where it is hollow.
Straight lines at 45 degree angle are drawn at
distance of 0.25 mm to indicate the mass and
the part that is hollow is kept plain
Also, in sectional view, no hidden lines are to
be indicated.
21. Aim:-Sketch-1, shows Isometric View of a
machine part. Draw its following
orthographic views using third angle
method of projections, giving
dimensions.
(1) Sectional F.V.-AA
(2) T.V.
(3) L.H.S.V
A
A
8
Φ20Φ36
A
A
LEFT HAND SIDE VIEW SECTIONAL FRONT VIEW AA
TOP VIEW
X
SCALE:- 1:1
SYMBOL OF PROJECTION METHOD, NOT SHOWN
Sketch-1
2 HOLES,Φ 14
Φ36
Φ20
R35
65
14`
100
AA
SOLUTION`
30
22. A
A
LEFT HAND SIDE VIEW SECTIONAL FRONT VIEW AA
TOP VIEW
SCALE:- 1:1
SYMBOL OF PROJECTION METHOD, NOT SHOWN
SOLUTION`
AA
100
8
Φ20Φ36
2 HOLES,Φ 14
X
Φ36
Φ20
R35
A
A
Aim:-Sketch-1, shows Isometric View of a
machine part. Draw its following
orthographic views using third angle
method of projections, giving dimensions.
(1) Sectional F.V.-AA
(2) T.V.
(3) L.H.S.V
14
30
Hatch (section) lines, to be kept at 1 to 1.5 mm apart,
at 45° normally, but depends on areas to be hatched.