Technical Drawing

We explain what technical drawing is, its characteristics and types. Also, what are the lines you use.

technical drawing
The technical drawing shows dimensions, shapes and characteristics of objects and materials.

What is technical drawing?

The technical drawing It is a branch of drawing that is dedicated to representing objects in a graphic and systematic way in order to provide detailed, clear and precise information about its construction and operation. It provides exact instructions that allow not only to manufacture objects or construct buildings, but also to carry out maintenance, analysis, repairs and improvements of finished designs.

In this sense, the technical drawing It is a representation system and a graphic language that is used to communicate in industrial, technological and design activities, both global ideas and very specific details.

Schemes, sketches, diagrams and plans are forms of technical drawing. Depending on the discipline, they may contain specifications corresponding to length measurements, angles surfaces, distance and others. The basic views in the technical drawing are usually the plan (view from above), the elevation, which can be front or side, and the sections or sections.

Likewise, scales (that is, the proportional relationship between the real dimensions of an object and its graphic representation) are essential in technical drawing, as they allow large-sized elements to be represented on a plane of reduced dimensions.

Technical drawing has very different characteristics and purposes than artistic drawing Artistic drawing is personal, subjective and free, while technical drawing aims to be objective, precise, systematic and normative.

The roots of technical drawing date back to Ancient Greece. Mathematicians such as Thales of Miletus, Pythagoras and Euclid developed the geometry of space and with it laid the fundamental foundations for the precise representation of three-dimensional objects in the two-dimensional plane. During the Renaissance, technical drawing flourished with the contributions of Filippo Brunelleschi and the famous Leonardo da Vinci.

Standards for technical drawing: There are standards and conventions pre-established by regulatory institutions that the technical drawing must comply with, such as ISO standards (International Organization for Standardization), ISA (Instrument Society of America) or DIN. (German Institute for Standardization, by its acronym in German), among others. These norms establish international standards that serve to unify criteria regarding the dimensions, shapes and characteristics of the pieces, buildings, spaces and materials.

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See also: Sketch

Features of technical drawing

The technical drawing has the following characteristics:

  • Look for precision. The technical drawing must be exact, rigorous and faithful to the dimensions and shapes of the actual design. It uses layout and measuring instruments, as well as standardized techniques, to clearly and completely convey the characteristics of a design.
  • It is based on international standards. Technical drawing uses a series of conventions that are valid for various disciplines throughout the world. Its symbols, lines and figures are regulated and systematized by international organizations, which has allowed the creation of a graphic language interpretable by professionals of any language and nationality.
  • Provides complete and necessary information. In technical drawing, graphical representations must be complete and specific, that is, they must provide all the data necessary to manufacture, assemble, repair or construct the represented model. Relevant information includes dimensions, finishes, material type and characteristics, as well as other technical details.
  • Use specific techniques and instruments. Technical drawing uses standardized techniques, such as sectioning, representation of views, projection and dimensioning. If done manually, these techniques require precision and the use of specialized instruments, such as squares, compasses, T-rules, scale meters, drawing pens, markers, bevels, pencils of different hardness and erasers, among others.

Digital tools: Currently, technical drawing is carried out mostly digitally in CAD (computer-aided drawing, for its acronym in English), through computer programs such as AutoCAD, DraftSight or QCad, which, due to their precision and efficiency, facilitate the creation, visualization and modification of plans and graphic representations.

Types of technical drawing

Technical Drawing
The architectural drawing is used to make construction plans for houses and buildings.

According to its uses and applications, technical drawing is classified into:

  • Architectural technical drawing It includes graphic representation for the construction of buildings, bridges and other architectural projects.
  • Mechanical technical drawing. It is used to make representations of the parts of automobiles, airplanes, motorcycles or industrial machinery.
  • electrical technical drawing It is used to represent simple electrical installations (such as those in a home) or complex ones (such as those in an industry). It usually indicates the location of the main panel, switches, outlets and other elements of electrical systems.
  • Geological technical drawing. It is used in geology and geography to represent the various layers of the Earth through a set of signs that allow us to indicate the minerals found in them.
  • Urban drawing It is used to functionally represent the development and infrastructure of cities and urban centers, existing or in the project stage.
  • Topographic drawing It is used to indicate characteristics of a terrain, such as height, slope, the presence of natural or artificial geographical features, elevations or contour lines.
  • Technical drawing of sanitary facilities. Its purpose is to represent all the sanitary facilities of a building (bathroom, shower, sink and so on), as well as the location of external and internal pipes.
  • Electronic technical drawing. It is used to graphically represent installation diagrams and operation schemes of small-scale electronic and electrical circuits.
  • Industrial design technical drawing It is used to graphically represent industrial products, containers, packaging, devices or furniture.
  • Cutting and sewing technical drawing. It is used to graphically represent patterns and indicate the measurements and construction details of clothing items.
  • Cartographic technical drawing. It serves to represent cartographic and topographic elements, that is, to detail the earth's surface precisely.

Lines used in technical drawing

technical drawing
The break line represents a long piece that appears shortened.

The line is a fundamental characteristic of technical drawing. There are different types of lines, among which are:

  • Contour line It is a thick, continuous line used to represent the outline of an object. It is usually between 0.7 and 1.5 millimeters, depending on the format and complexity of the drawing.
  • Break line. It is a line that is used to present the view of an object when its representation does not fit on the plane. It is usually between 0.5 and 0.7 millimeters, and is made with small sawtooth-shaped strokes 2 to 3 millimeters long.
  • Hidden line. It is a thin, segmented line that represents corners, edges, or vertices of objects that are not visible from the represented point of view.
  • Flat cutting line It is a thick, dashed line used to indicate the precise location of a cut or section that is made imaginary on the plane to show the interior of an object.
  • Center line. It is a thin line used to show symmetrical features, hole centers and axes.
  • Dimension or dimension line. It is a fine line that is used to delimit the measurements of objects.
  • Guide or reference line. It is a thin line used to indicate the place on the object to which a note corresponds. The notes inform about dimensions, materials and other details.
  • Virtual or ghost line. It is a dashed line used to suggest displacement or alternating positions on pivots or moving parts.
  • Section or cut line. It is a thin line inclined at 45 degrees that is drawn repeatedly, in the form of a pattern, to indicate the place that simulates the cutting of a piece.

Applications of technical drawing

Technical drawing is used in various disciplines. In architecture, it is a fundamental tool for presenting a design, in order to construct the building as the architect conceived it. This requires graphic representations of the facades, sections or cuts, the distribution of spaces and all construction details. In the case of interior design, the technical drawing is used to represent the finishes, spaces and furniture distribution.

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The different branches of engineering also use technical drawings to represent parts, structures, circuits, materials and procedures, in order to provide the necessary information for construction, manufacturing and maintenance processes.

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References

  • Bielefeld, B and Skiba, I. (2013). Basics Technical Drawing. Birkhäuser.
  • Company, P and Vergara, M. (2008). Technical drawing. Publications of the Jaume I University.
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