What is the purpose of engineering drawing?

What are the main types of engineering drawing?

The purpose of an engineering drawing is to convey information about an object accurately and clearly. It expresses the details of an item from one person to another. This is especially important when we consider that engineers must be able to understand each other regardless of the language that we speak.

Isometric

Isometric drawings are representations of a design, shown in a single 3D view. 'Callouts' (labels) in conjunction with a data or information table can enhance the drawing to give additional information, for example manufacturing processes or materials.

Example Isometric Drawings -

Embossing Tools. This was a manufacturing project done by GCSE Industrial Technology Students at Cynffig some years ago. Each tool is different but each has been drawn in the same way - isometric. You can see that there are no dimensions (sizes). This is because isometric drawings are not done to scale.

Drawing circles (becoming ellipses in isometric)

When a circular detail or face is moved at an angle, to the eye it becomes elliptical (an ellipse). There is an accurate, but slightly 'fiddly' way of sketching an isometric circle (an ellipse). The PowerPoint below explains the method. There is an accompanying worksheet (print off slide 1 of the 2nd PowerPoint).

Isometric drawing practice exercises

If you wish to practice drawing using isometric, the exercises below will help you hone your skills. Clicking this link will enable you to download some isometric paper to practice on.

Using the three tone shading technique when you've finished, helps to make the sketches 'jump off the page'.

The rule for this method of shading is that each surface (face) can only exist in one of three 'orientation planes'. If a face is in the same orientation as another then it has the same shading. Because of this, there can only be three tones: light, medium & dark.

We tend to shade the face which is pointing to the (imaginary) light source as the lightest.

What is the difference between a third angle projection and a first angle projection?

A nice way of differentiating between a third angle and a first angle projection is by remembering the following silly rhyme: " For All Perfect Bread, Think And Plan Ahead". This stands for: First angle - Plan view (goes) below, Third angle - Plan view (goes) above.

How do we make sure that everybody conveys information correctly?

In order to ensure that no confusion exists when sharing information between different engineers around the world, we make use of engineering conventions. These are rules and guidelines which everybody follows. Whilst there are different standardisation organisations in each continent, the main ones we need to be aware of in the UK are ISO (International Standards Organisation) and the British Standards Institute (BSI).

For engineering drawings, the main regulations are: BS8888 and ISO128.

Dimensioning (adding important sizes to a drawing)

These two (blurry) posters give a good overview of the most frequently used methods for adding important sizes to a drawing. Fortunately when creating a drawing using software like Fusion 360 it will automatically add the dimensions in the correct format for you, however it is important in industry to have a good understanding of the accepted 'conventions' (rules).

Line Types

Lines types are a very powerful way of adding important engineering information without 'overloading' the drawing with excessive clutter. The drawing below shows the 12 main lines types used in engineering drawing. Learn them well. They are VERY important.