Technical and engineering drawings express precise requirements or specifications that should be easy to interpret. There are certain types of lines used for graphical communication in technical and engineering drawing in order to convey clear messages, and abide by good professional standards. Generally, most of the lines used in practice are of uniform thickness and density.
It is vital for drafters, designers, engineers, and people to understand how and when to apply the variety of line styles which serve as a reliable means of passing on valuable information when drawn and positioned properly on drawing paper or computer.
Most objects drawn in technical and engineering drawing practice are somewhat complicated and contain a lot of planes, surfaces, and edges. In order to clearly distinguish all of them, it is important to use technical and engineering drawing lines effectively.
Lines make the difference; they are fundamental and perhaps the most important thing in technical and engineering drawings because they express or illustrate how shapes and sizes of objects would in real life after they are constructed.
In many cases, if every line has the same thickness, technical and engineering drawings would be confusing and difficult to interpret because some very important planes and parts of objects won’t stand out from dimension lines that describe only the outlook of objects.
By employing different types of lines on the basis of various thicknesses and designations, many features can be expressed in precise ways which would otherwise be difficult to express. To make sure everybody can interpret drawings the same way, the use of different types of lines was established decades ago by various committees that recognize the importance of standardization in technical & engineering drawing.
The most popular types of lines form the core of technical and engineering drawings. Some lines are dark, while others are light; some are thick, while others are thin; some are solid all through, while others are dashed in various ways.
The figures below illustrate the types of lines popularly used in technical and engineering drawings.
Figure 1: 8 types of lines used in technical & engineering drawing
Figure 2: 4 extra types of lines used in technical & engineering drawing
Figure 3: Other types of thin lines used in technical & engineering drawing
Figure 4: Hatching & cutting plane lines used in technical & engineering drawing
Figure 5: Example of a drawing that uses 6 different types of lines