ISOMETRIC PROJECTION
•It is a method of producing pictorial view of an
object showing all three faces of the object
simultaneously.
•It is a type of parallel projection
•It is a type of axonometric projection
ORTHOGRAPHIC ISOMETRIC
450
300
ISOMETRIC DRAWING A TYPE OF PICTORIAL PRESENTATION
AXONOMETRIC PROJECTION
ISOMETRIC
TRIMETRIC
DIMETRIC
CONSTRUCTION OF ISOMETRIC SCALE
• Draw a horizontal line AB.
• From A draw a line AD at 45o to represent actual or true
length and another line AC at 30o to AB to measure
isometric length.
• On AD mark the point 0, 1, 2 etc to represent actual
lengths.
• From these points draw verticals to meet AC at 0 , 1 , 2
etc. The length A1 represents the isometric scale length
of A1 and so on.
AB/AD = COS 45 AND AB/AC = COS30 degree
Cos45/cos30 = 0.81
Isometric Length = 0.81 × Actual Length
All the dimensions measured along or parallel to isometric axes (-X, -Y and -Z) will taken as Isometric Length.
METHODS OF CONSTRUCTING ISOMETRIC
PROJECTION
BOX METHOD -
• When an object contains a number of non-isometric lines, the isometric drawing may be conveniently constructed by using the box method. In this method, the object is imagined to be enclosed in a rectangular box and both isometric and non-isometric lines are located by their respective points of contact with the surfaces and edges of the box.
OFF-SET METHOD -
• Off-set method of making an isometric drawing is preferred when the object contains irregular curved surfaces. In the off-set method, the curved feature may be obtained by plotting the points on the curve, located by the measurements along isometric lines.
REPRESENTATION OF BOX METHOD
PENTAGON IN A BOX • DRAW ORTHOGRAPHIC PROJECTION (MULTIVIEW –
TOP VIEW /FRONT VIEW) OF THE GIVEN PENTAGONAL
PRISM ASSUMING AXIS IS PERPENDICULAR TO HP/VP.
• LEVEL THE VIEWS AS A, B, C, D & E.
• DRAW HORIZONTAL AND VERTICAL LINES THROUGH
EACH CORNERS (A, B, C, D & E) OF PENTAGON (TOP
VIEW).
• THESE HORIZONTAL AND VERTICAL LINES WILL FORM
A RECTANGLE (BOX) – 1,2,3,4 IF EXTENDED.
• Redraw/transfer the rectangle 1234 in isometric view.
• Draw edge 12 and 23 of rectangle inclined at 300 (iso-angle)
to ground/xy-line. Subsequently, mark point 4 and complete
the rectangle.
• TRANSFER POINTS A,B,C,D AND E OF PENTAGON ON
RECTANGLE 1234.
ISOMETRIC VIEW OF A PENTAGONAL
PYRAMIS STANDING ON HP
1. HEIGHT IS ADDED FROM CENTRE OF PENTAGON IN ISOMETRIC VIEW. 2. Invisible edges/lines like O’D are not drawn.
O’
REPRESENTATION OF FOUR POINTS/OFFSET METHOD
P P
Q
P
Q R
R
S S
ISOMETRIC PROJECTION OF CIRCLE
THROUGH FOUR POINTS METHOD
STEPS – 1. DRAW THE CIRCLE OF GIVEN RADIUS.
2. Enclose the circle in a Rectangular Box by drawing horizontal and vertical lines being tangent on circle.
3. Redraw the rectangle, PQRS on isometric axis keeping QP and QR inclined at 300 to ground.
4. Draw mid normal on QR and QP through point S as SC and SD. Also, draw mid normal on SP and SR through point Q as QA and QB.
5. 1A & 2D will intersect each other at point 3 and 1B & 2C will intersect each other at point 4.
6. Draw arcs keeping 1 as centre and 1A/1B as radius, 2 as centre and 2C/2D as radius, 3 as centre and 3A/3D as radius and 4 as centre and 4B/4C as radius.
7. Join the arcs to get the isometric projection of a circle, which will be an ellipse.
ISOMETRIC PROJECTION OF CIRCLE
THROUGH OFF-SET METHOD
STEPS – 1. DRAW THE CIRCLE OF GIVEN RADIUS.
2. Enclose the circle in a Rectangular Box, ABCD by drawing horizontal and vertical lines through points 1,3,5 &7 being tangent on circle.
3. Join bD and Ac which will cut the circle at 2 & 6 and 4 & 8.
4. Draw tangents or horizontal/vertical lines through points 2,4,6 & 8 which will cut rectangle, abCD at points F, G, H, I, J, K, L &E.
5. Redraw the rectangle, ABCD on isometric axis keeping AB and AD inclined at 300 to the ground.
6. Transfer all the points of abCD on ABCD.
7. Join points 1, 2,3,4,5,6,7,8 and 1 through a smooth curve, to get the isometric projection of a circle, which will be an ellipse.
A square prism base side-40 mm, height-50 mm is
placed centrally on a rectangular slab sides-100 mm x
60 mm and thickness-20 mm. Draw the isometric
projection of the combination.
Plan and Elevation of combination
Isometric projection of combination
A pentagonal pyramid of base side-30 mm, and
axis length-60 mm is resting on HP on its base
with a side of base perpendicular to VP. Draw the isometric projections.
A frustum of cone base diameter-50 mm, top diameter-25 mm
and height-50 mm is placed centrally on a cylindrical slab of
diameter-100 mm and thickness-30 mm. HP on its base with a
side of base perpendicular to VP. Draw the isometric projection of the combination.
ASSIGNMENT
DRAW ALL THE PROBLEMS OF THE PROBLEM SHEET ON ISOMETRIC PROJECTION DISTRIBUTED IN
THE CLASS
