Technical Drawings in Interiors

TECHNICAL DRAWINGS IN INTERIORS 4(1+3)

Lesson 5:Axonometric Projection Drawings

Isometric drawings

The three principal faces and axes are equally inclined to the plane of projection (Figure – 1)

The term "isometric" comes from the Greek for "equal measure", reflecting that the scale along each axis of the projection is the same (this is not true of some other forms of graphical projection). The word isometric means "having equality of measure". This means that the object is placed with its major edges at equal angles with the drawing plane.
In isometric pictorials, the direction of viewing is such that the three axes of space appear equally foreshortened, of which the displayed angles among them and the scale of foreshortening are universally known. Isometric projection is a form of graphical projection, more specifically, a form of axonometric projection. It is a method of visually representing three-dimensional objects in two dimensions, in which the three coordinate axes appear equally foreshortened and the angles between any two of them are 120 degrees. ( Figure – 2)

• The object is revolved 45° to the horizontal.
• The object is tipped up or down 35°16’.
• Lines are drawn to true length
• Axes equally separated (120° )
• H W and D measurements are true size along iso axes
• Angles must be coordinates
• Circles appear as ellipses on all surfaces

True measurements are made along three major axes Figure – 3, which are:

1. VERTICAL
2. 30 degrees up to the LEFT
3. 30 degrees up to the RIGHT

• A circle drawn in isometric has the shape of an ellipse on any of the three faces (Figure – 4)

1. Isometric Drawings
2. Lengths and breadths are drawn at 30° to the horizontal.
3. Heights are drawn vertically.
4. All sizes are drawn to their exact sizes.
5. Circles cannot be drawn using compasses.