Introduction to Technical Drawing

Technical drawing is a way of representing mechanical information about objects. It allows describing shapes, sizes, thicknesses, positions and many other details of these objects. With the technical drawing you can represent from the small screw of a wristwatch to a whole skyscraper.

The earliest known technical drawings are over four thousand years old and were used to assist in the construction of buildings. Nowadays, technical drawings can be found anywhere, like on the plans to assemble Ikea furniture or on emergency exit signs.

Technical drawing as language

Another way of looking at technical drawing is as a language with which we can store and transmit information. Writing allows us to represent the ideas we are talking about, this being more demanding because when writing it is necessary to think better about what we want to say. When rereading what we have written later, it is common for us to come up with a better way of expressing ourselves or some detail that we do not reflect. In other words, it also helps us to continue thinking and improving.

Technical drawing has characteristics similar to writing. Drawing an object forces us to think about the details of what we are representing. Later, when looking at the drawing again, we can remember ideas that we forgot to represent or failures to improve. This allows the design to be a cumulative process, in which details are added little by little until we reach the final design. Doing this from memory would be something so complex that very few people could do it.

Technical drawing as a written language helps us to:

  1. Think more precisely and accurately
  2. Record ideas to remember them later
  3. Communicate our ideas to others
  4. Refine designs by adding enhancements

Types of drawings

Sketch

It is the drawing of an idea made freehand. It is schematic, so it does not have details or measurements.

The advantage of the sketch is that something can be drawn even if the idea is only schematic and not clear.

Preliminary plan

It is a freehand drawing of an object. It has all the necessary measurements and details to describe it and is drawn with the correct proportions. It is drawn more precisely and clearly than the sketch.

The preliminary plan is used to manufacture the object it represents.

Plan
A plan is a drawing made with drawing instruments or by computer. It is similar to a preliminary plan, but cleaner. The plan is drawn to an exact scale.

Definitions

Dimension

To dimension is to add to the drawing the size of the real object. If an object is 20 millimeters in size, that amount will be represented in your drawing.

If the drawing is larger than the object (enlargement) or smaller (reduction), the dimension always has the same value because it does not depend on the size of the drawing. The dimension represents the size of the actual object, not the size of the drawing.

Scale
A scale drawing is a drawing larger or smaller than the object it represents. For example, a map represents a country at a much smaller size, it is drawn at a reduced scale. The drawing of a cell is much larger than a cell, it is represented with a magnification scale.
Views
Views of an object are drawings of the object seen from different points. The elevation represents the object when we see it from the front. The profile represents what we see of the object from the side. The plant represents what is seen from above.
Perspective
A perspective drawing is a drawing in three dimensions. Allows you to see multiple views of the object at the same time.

Exercises

  1. Explain the differences between sketch and sketch
  2. Explain the differences between sketches and blueprints.
  3. Explain the similarities between sketch and sketch
  4. Draw a sketch of an everyday object (for example, a pencil, a spoon, a chair, a key, etc.)
  5. Draw a sketch of the previous object