National Institute of technology Jamshedpur-831014 ,Jharkhand ,india

DR. Parmanand Kumar

DEPARTMENT OF MECHANICAL ENGINEERING

ENGINEERING GRAPHICS

FOR -(2 SEMESTER) PRODUCTION ENGINEERING BATCH-(2019)

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 DRAWINGA 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-isometriclines, the isometric drawing may be convenientlyconstructed by using the box method. In this method, theobject is imagined to be enclosed in a rectangular boxand both isometric and non-isometric lines are locatedby their respective points of contact with the surfacesand edges of the box.

OFF-SET METHOD -

• Off-set method of making an isometric drawing ispreferred when the object contains irregular curvedsurfaces. In the off-set method, the curved feature maybe obtained by plotting the points on the curve, locatedby 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 OFPENTAGON IN ISOMETRIC VIEW.

2. Invisible edges/lines like O’D are not drawn.

O’

REPRESENTATION OF FOUR

POINTS/OFFSET METHODPP

Q

P

QR

R

SS

ISOMETRIC PROJECTION OF CIRCLE

THROUGH FOUR POINTS METHODSTEPS –

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 QPand QR inclined at 300 toground.

4. Draw mid normal on QR and QP through point S as SC andSD. Also, draw mid normal on SP and SR through point Qas QA and QB.

5. 1A & 2D will intersect each other at point 3 and 1B & 2C willintersect each other at point 4.

6. Draw arcs keeping 1 as centre and 1A/1B as radius, 2 ascentre and 2C/2D as radius, 3 as centre and 3A/3D asradius 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 METHODSTEPS –

1. DRAW THE CIRCLE OF GIVEN RADIUS.

2. Enclose the circle in a Rectangular Box, ABCD by drawinghorizontal and vertical lines through points 1,3,5 &7 beingtangent 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 points2,4,6 & 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 ABand AD inclined at 300 to theground.

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 anellipse.

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.