This course is about thinking and analysing, but this is
going to be slightly different in the sense that we are going to be thinking
and analysing only through geometry no equations, no analysis, no deduction,
but only through geometry, through drawings
You know long very long time ago, people expressed their
ideas through sketches and paintings they probably did not have the grammar.
They did not have the vocabulary they first of all started discussing or
presenting or expressing the ideas using sketches and paintings.
The representation of
the object in figure 2 is called an isometric drawing. This is one of a family
of three-dimensional views called pictorial drawings. In an isometric drawing,
the object's vertical lines are drawn vertically, and the horizontal lines in
the width and depth planes are shown at 30 degrees to the horizontal.
an isometric view, you are looking at an object from one of its corner.
orthographic view is different. When you look at an orthographic view of an
object, you look at the different faces of the object straight on, as if you
are facing that side of the object. You are usually given more than one
orthographic view of an object.
As a general guideline to dimension, try to think that you would make
an object and dimension it in the most useful way. Put in exactly as many
dimensions as are necessary for the crafts-person to make it -no more, no less.
Do not put in redundant dimensions. Not only will these clutter the drawing,
but if "tolerances" or accuracy levels have been included, the
redundant dimensions often lead to conflicts when the tolerance allowances can
be added in different ways.
measuring from one point to another will lead to inaccuracies. It is often
better to measure from one end to various points. This gives the dimensions a
reference standard. It is helpful to choose the placement of the dimension in
the order in which a machinist would create the part. This convention may take
Every drawing sheet is to
follow a particular layout. As a standard practice sufficient margins are
to be provided on all sides of the drawing sheet. The drawing sheet
should have drawing space and title page.
is a wide variation in sizes for engineering objects. Some are very large (e.g.
Aero planes, rockets, etc) Some are very small (wrist watch, MEMs
There is a need to reduce or enlarge while drawing the objects on paper. Some
objects can be drawn to their actual size. The proportion by which the drawing
of an object is enlarged or reduced is called the scale of the drawing.