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Technical drawings and their importance in industry

Measurement News from Q-Tech

General information about technical drawings

Technical drawings are important in many areas of industry, but especially in mechanical design. The technical drawing represents the conclusion of the work of a designer or a technical draftsman on a component. With the technical drawing all qualitative and quantitative characteristics of a component, an assembly or
machine and plant are to be made understandable to other persons and a reproducible manufacturing of the components is to be made possible. In general, all product details are clearly recorded in the technical drawing. 

What is a technical drawing? A technical drawing is a detailed image of already existing or planned components, which are required for the production of complex machines, for example. 

To be able to read and understand the drawing, special knowledge is required. The symbols used and the required standards play an overriding role, as does the software with which the technical drawings are created in this day and age.

What is a technical drawing? 

The technical drawing is a written document and means of communication between engineers and the manufacturing department in a company. It contains true-to-scale illustrations with dimensions and explanations. It is intended, for example, to show the functional or construction methods of individual parts and assemblies.

The goal of the technical drawing is a standard-compliant representation of an object. The drawing must be unambiguous. Only in this way can it be used to manufacture a depicted component. The creation of technical drawings is typical for engineers, designers, architects, draftsmen, etc..

The history of technical drawing

The most famous representative of technical drawings in the 15th century AD was Leonardo da Vinci. He recorded his numerous inventions, such as his war machine, a flying machine or a link chain in countless technical drawings. Today's basic knowledge of geometry and its research goes back far before the birth of Christ. Pythagoras of Samos and Euclid of Alexandria led the way.

More recent evidence of technical drawing can be found around 1700 in the work of the French aviation pioneer Jacques de Vaucanson and in patent specifications from the 19th century.

The knowledge of technical drawing has developed further and further over the last centuries. Numerous tools were established that made it easier and easier to create drawings. Whereas drawing boards, ink pens, stencils, curve rulers and tracing paper or transparent drawing foils were mainly used for this purpose in the past, the age of computers has seen the establishment of more and more computer-aided drawing programs (CAD).

Today, it is not uncommon for the reverse route to be taken: from the finished product back to the precise technical drawing. Reverse engineering is used to examine and measure the outer and inner contours of finished components and industrially produced products. From the data obtained, corresponding specialist companies, such as Q-Tech in particular, generate precise 3D CAD models, which in turn form the basis for the technical drawing. Especially in the case of missing CAD data or spare parts, this is a great facilitation of work.

Overview and basics of technical drawings

To ensure that technical drawings are clear and comprehensible everywhere, certain basic principles, representation rules and dimension entries must be observed. These are summarized in various standards, which regulate the exact structure of a technical drawing. One of these guidelines is, for example, the DIN standard of the Deutsches Institut für Normung e. V. (German Institute for Standardization), which is to be used as a binding aid when creating shapes and dimensions. 

Where are technical drawings used?

Although today many goods, commodities or devices are produced with the help of other manufacturing machines, technical drawings are still indispensable. Because these fulfill important, central tasks:

  • Technical drawings provide a pictorial representation of product features that cannot be correctly reproduced in 3D CAD models. These can be internal or external threads, for example.
  • The numerous notes, dimensional and tolerance specifications provide the cutting machine operator with a comprehensive picture of the component to be produced.
  • Important tolerance deviations from the standard are thus clarified.
  • For example, the designer can use the drawings to communicate certain requirements, such as surface roughness, to the manufacturer or production.

Therefore, the drawings are needed especially in areas where high accuracy and minimization of risks due to a faulty design are important. This is especially the case in mechanical engineering and also in technical documentation.

In mechanical engineering, technical drawings are required for the following purposes:

  • For the production of components
  • For the representation of components
  • During assembly
  • For repairs
  • For brochures
  • For computer animation with CAD (Computer Aided Design)

Technical drawings are required for the documentation of machines, systems and other products, especially if a CE declaration of conformity is required for placing the product on the market within the European Economic Area. The drawings are used to illustrate in detail all the functions, operation and possible sources of danger of a product.

What are the types of technical drawings?

Depending on the purpose, different types of representation are preferred for technical drawings. These can be:

  • Line drawings
  • Functional drawings
  • Exploded views
  • Real representations
  • Sectional drawings
  • Flowcharts

What belongs in a technical drawing?

Technical drawings contain the following elements: coordinates, title block, orthogonal views of the part, sectional views, detailed views and other notes for manufacturing.

The title block

The title block is always located in the lower right corner of a technical drawing. It contains all the basic information, including the product name, the names of all parties involved (design, testing and approval) and the name of the relevant company. Also noted in the title block are technical details about the dimensional system used, the projection angle, surface finish requirements, scale and material.

The coordinates

Especially with large and complex technical drawings, coordinates are noted in the margin for better orientation, for example in meetings.

The orthogonal view

The orthogonal view, also called orthogonal projection, contains the most important information about the geometry of the part. Thus, the dimensions and tolerances can be found in it. The orthogonal view corresponds to a two-dimensional image of the three-dimensional object from different angles. Typical for this are: 

  • A front view
  • A rear view
  • A side view
  • A top view
  • One bottom view

In the orthogonal projection, hidden lines of important components can also be drawn. As a rule, two or three orthogonal views are sufficient for the correct reproduction of the geometry.

The isometric representation

The isometric representation is a three-dimensional, graphical representation of the object. Even if the isometric representation is not mandatory, it should still be included in technical drawings in practice. This is because it provides the mechanics with additional information, such as the assembly direction.


Section views are two-dimensional images of selected areas, a part of which has been cut off so that the internal features of the component, which are not apparent from either the isometric or orthogonal view, can be made visible. As a rule, the sections are positioned in line with the orthogonal views.

The imaginary cutting edge and cutting direction are indicated in the orthogonal projection with a labeled line. The resulting cut surfaces are marked with hatching. For complex parts, it is not uncommon for several section views to be displayed.

Detail view

If the orthogonal projection contains complex features and areas that are difficult to recognize, these areas can be displayed in more detail with additional detail views. Detail views may differ in size and orientation from the orthogonal views. For better assignment, detail views are marked with a single letter that identifies the respective area of the orthogonal view.

Notes to the manufacturer

Notes for manufacturing are usually placed on the lower left side of the technical drawing above the title block. This contains all information that is not apparent from the drawing. This can be instructions to the machinist, such as deburring, chamfering, or surface finishing.

What scale is used in an engineering drawing?

Technical drawings of workpieces often have a scale of 1:1, which means that the drawing is the same size as the workpiece. For larger workpieces, the drawing is reduced accordingly. Depending on the size of the workpieces, the following scales are selected according to DIN 823:

  • Reductions are made in the scales M 1:2, M 1:10, etc.
    The scale M 1:10 means that 1 mm of the drawing corresponds to a real length of 10 mm. This makes the drawing only as large as one tenth of the workpiece.

For very small workpieces, the technical drawing is enlarged accordingly:

  • Enlargements are made in the scales M 2:1, M 10:1, etc.
    The scale M 10:1 means that 10 mm of the drawing correspond to a real length of 1 mm. Or: The drawing is ten times larger than the workpiece.

Important symbols on technical drawings 

Information in technical drawings is represented by numerous symbols. There are:

  • Font symbols
  • Punctuation
  • Digits
  • Surface finishing symbols
  • Connection symbols (rivet or screw symbols, welding symbols)
  • Roughness, dimensioning and tolerance symbols
  • Component symbols (bolt, rivet, spring symbols)
  • Assembly symbols (rolling bearing, motor, gearbox symbols)
  • Machine, apparatus, device symbols

It is important that the labeling of a drawing is always readable in the same direction as the reading direction of the title block. 

The symbols and their meaning are in turn regulated in numerous standards. The same applies to their representation. For example, the dimensions of symbols for welding drawings or surface treatment symbols must not be changed. On the other hand, there are other symbols whose dimensions must be adapted to the component.


What are the symbols?

By means of the symbols geometrical tolerances can be defined in the technical drawings. A distinction is made between: 

  • Shape tolerance (shape deviation)
  • Alignment tolerance
  • Position tolerance (position deviation)
  • Concentricity tolerance 

In this context, the symbol describes the respective geometric properties. Thus, a straight surface (straightness) is represented by a straight line, a roundness by a circle. Planes, on the other hand, are clarified by means of a parallelogram. 

In addition, parallelism, perpendicularity, angularity, symmetry, concentricity and numerous other properties can be visualized with corresponding symbols. 

The technical drawing and its importance in the industry

The technical drawing cannot be compared with a normal picture. Rather, the drawing is a transmitter of ideas and information. Due to the prescribed standards, a technical drawing is sometimes even more precise and unambiguous than many a spoken word. Especially for the production of machines, but also in electrical engineering or construction, these drawings are indispensable. Nowadays, CAD software is usually used to create them. This means that dimensions and tolerances can be entered directly on the virtual model. This not only speeds up work processes - in the meantime, the technical drawing has become an international means of communication in technology, since the respective DIN standards take into account the recommendations of the International Organization for Standardization (ISO).