Definition & types of technical drawing (PDF download available)

This article defines technical drawing (drafting or projection) and uses different images to illustrate the meaning, and types of technical drawing widely taught in schools and practiced in industries. The eBook/technical drawing PDF document of this article can be obtained at the end of this article. (Featured image credit: Pixabay.com)

This article defines technical drawing (drafting or projection) and uses different images to illustrate the meaning, and types of technical drawing widely taught in schools and practiced in industries. The eBook/technical drawing PDF document of this article is available to download for free. Although it contains all the information available in this article, it still has something extra on its last (17th) page: a link to hundreds of images of objects in 2 & 3 dimensions, and under different types of projections. Basically, both the article and eBook elaborate on the following:

  • Definition of technical drawing.
  • Types of technical drawing: parallel projection (orthographic—first angle, and third angle; oblique—cavalier, and cabinet; axonometric—isometric, dimetric, and trimetric), and perspective projection (1 point, 2 point, and 3 point).
  • Objectives of technical drawing.
  • Purpose of technical drawing.
  • Application of technical drawing.

If you are interested in downloading the eBook of this article, which also contains a link to hundreds of various shapes and sizes of objects in 2 & 3 dimensions, click here and download it for free. (Download Instructions: In order to download successfully, after you click the link above, or any of the links below, also click the “Skip AD” button that will appear after a few seconds around the top right corner of your screen, and the file will appear for download. Alternatively, if the “Press allow” button appears, click “allow” so that the file(s) will appear for download.)

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For further reading, you may download the best books on technical and engineering drawing by clicking the following links.

Download PDF: Technical Graphics Communication by Bertoline, Wiebe, Hartman & Ross

Download PDF: Interpreting Engineering Drawings by Branoff, Theodore J.

Download PDF: Manual of Engineering Drawing by Simmons & Maguire

1.0 Definition of technical drawing

Technical drawing can be defined as the graphic representation of an object, concept or idea using a universal language that consists of graphic symbols produced with the aid of drawing equipment/tools that can be used to measure straight and curved lines according to specified dimensions, scales, and codes of practice.

Technical drawing is used in many professions (engineering, architecture, manufacturing, construction, estate management, etc.) to draw or draft ideas and different views of physical objects like drainages, culverts, septic tanks, incinerators, houses, etc. Drawing—either artistic or technical—is one of the oldest forms of communication, and is believed to be older than verbal communication. Generally, there are two types of drawings: artistic drawing, and technical drawing:

Artistic Drawing

Artistic drawing is the type of drawing that is abstract because its meaning is unique to the person/artist who creates it. In order to understand the meaning of an artistic drawing, one has to understand the artist’s point of view or motivation for producing a specific artistic drawing.

Sometimes, it is necessary to understand an artist in order to understand their artistic drawing because artists often take a unique/abstract approach when communicating through their drawings. This type of approach gives rise to various interpretations when their drawings are exposed to public view.

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All articles on technical drawing with engineering graphics

Regardless of how complex artistic drawings may appear, they express the clear feelings, beliefs, philosophies and ideas of the artists who create them. Artistic drawings are generally freehand drawings or drawings made without the use of drawing instruments/tools.

Technical Drawing

Technical drawing is the type of drawing that is not abstract because it doesn’t require an understanding of what its creator has in mind; rather, it requires an understanding that can only be gained by studying and using universally accepted tools, codes and conventions applicable to technical drawing.

In addition to the previously stated definition on technical drawing, we can say that technical drawing clearly, precisely and concisely communicates all important information conveyed by an idea produced in graphic form by the use of universally accepted codes of practice, tools, dimensions, notes, symbols, and specifications.

Technical drawing can be done manually, or with the use of computers. When any idea or object is drawn on computer, it is said to be drafted by computer aided design (CAD). One major advantage of using CAD is that revisions can be easily and speedily carried out on any draft.

Any student, architect, engineer, etc., must understand the theory behind projections, dimensioning, and conventions if they wish to become proficient in drafting and interpreting drafts. It is very important for people to understand manual (traditional) drawing/drafting before exposing themselves to CAD softwares. Why? Because an understanding of manual drawings would make it easier to use CAD.

2.0 Types of technical drawing

Technical drawings are constructed on the basis of fundamental principles of projection. There are two main types of technical drawing or projection: parallel projection, and perspective projection. (Note that each projection has various categories that will be illustrated further below.)

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A projection is any drawing, draft or representation of an idea or object that is carried out after considering views from various imaginary planes. Projections, which are quite similar to the direct views that one can see on televisions, can be used to represent actual objects if the following are employed:

  • the eye of the viewer looking at the object.
  • an imaginary plane of projection as dictated by the direction of the eye(s) of the viewer.
  • projectors or imaginary lines of sight.

The theories behind projection have been widely used to draft 3-dimensional objects on 2-dimensional media such as papers and computer screens. The theory of projection is based on two variables:

  • line of sight.
  • plane of projection: plane from which images can be projected—depending on the axis.
Figure 1: Lines of sight: parallel and perspective projections
Figure 1: Lines of sight: parallel, and perspective projections
Chapter 1_Figure_2_ planes of projection for parallel and perspective projectionssss.jpg
Figure 2: Planes of projection: parallel, and perspective projections

2.1   Parallel Projection

Parallel projection is the type of projection in which the lines of sight or projectors are parallel to each other, and also perpendicular to the planes of objects or images. Parallel projection can be categorized or divided into orthographic, oblique, and axonometric projections.

(1) Orthographic projection

Orthographic projection (or drawing) is the type of projection in which 3-dimensional objects are represented in 2 dimensions by projecting planes (consisting of 2 major axes) of objects so that they are parallel with the plane of the media they are projected on.

Orthographic projection can also be defined as the type of projection in which views are taken on different planes of objects and drawn (or represented) in 2 dimensions as illustrated by the principal views shown in the figures below:

Chapter 1_Figure_3_three major views of orthographic projection.jpg
Figure 3: Three major views in orthographic projection
Chapter 1_Figure_4_six general views of orthographic projection.jpg
Figure 4: Six general views in orthographic projection

There are two types of orthographic projection: first angle projection, and third angle projection:

In first angle projection (i.e., European/international system) the front view is placed at the top of a medium (paper, computer screen, etc.) along with the right side view which is placed at the left side of the front view, while the left side view is placed at the right side of the front view, and the plan (T) is placed alone beneath the front view.

In third angle projection (i.e., American system) the plan (T) is placed alone at the top, while the front view is placed beneath the plan, and the right side view is placed at the right side of the front view, while the left side view is placed at the left side of the front view. (Note that third angle projection is more popular than first angle projection.)

Chapter 1_Figure_5_first and third angle projections
Figure 5: First angle, and third angle projections

If you would like to read more details about orthographic projection or drawing, click here.

(2) Oblique projection

Oblique projection is the type of projection in which any object is drawn in 3 dimensions, with each of the 3 dimensions (or major planes) consisting of two lines (or major axes: either xy, or yz, or xz) perpendicular to each other (i.e. 90°), and one of the 3 planes parallel to the plane of paper, or computer screen, etc.

In addition, one of the 3 planes is projected at either 30°, 45° or 60° to the x axis. Oblique projection is of 2 types: cavalier, and cabinet projection.

Chapter 1_Figure_6_oblique_cavalier_cabinet projections.jpg
Figure 6: Oblique projection: cavalier, and cabinet projections

In cavalier projection, one of the 3 planes is drafted to represent a plane of an object “according to a given scale”, while in cabinet projection, one of the 3 planes is drafted to represent half of a plane of an object “according to half of a given scale”. A scale is any ratio (examples: 1:10, 1:100, 1:1000, etc.) of the size of an object on paper to the actual size of the same object in real life.

Chapter 1_Figure_7_oblique projection with orthographic views.jpg
Figure 7: Oblique projection with orthographic views

(3)   Axonometric Projection

Axonometric projection is the type of projection that consists of three-dimensional drawings in which each of the 3 major axes (x, y, and z) of an object is drawn perpendicular to each other by either 30°, 45°, or 60°, and no plane of the object is drawn parallel to the plane of media—paper, computer screen, etc. Axonometric projection/drawing can be categorized into three types: isometric, dimetric, and trimetric projections.

Download PDF: Technical Drawing with Engineering Graphics and Design in Practice_Definitions, Importance, and Applications

Isometric projection is a method of projection/drawing in which the edges of 3-dimensional objects are represented by 3 axes perpendicular to each other and inclined to each other by 120° on the plane of media—paper or computer; also, 2 of the 3 axes are inclined at either 30°, 45°, or 60° to any imaginary x axis on any media.

In dimetric projection, 2 angles between any 2 major axes are unequal, while in trimetric projection, the 3 angles between the 3 major axes are unequal. Two different angles are required to construct 2 planes of objects in dimetric projections, while 3 different angles are required to construct 3 planes of objects in trimetric projections.

Chapter 1_Figure_8_Axonometric projection_Isometric_dimetric_trimetric
Figure 8: Isometric, dimetric, and trimetric projections

2.2   Perspective Projection

Perspective projection is the type of projection in which objects appear smaller as their distances from an observer increases: objects dimensions along a line of sight appear shorter than they actually are.

There are 3 types of perspective projections: 1 point, 2 point, and 3 point projections. One point perspective projections consists of 1 vanishing point, while 2 point and 3 point perspective projections consist of 2 and 3 vanishing points, respectively.

A vanishing point is a point of convergence where all lines of sight meet.

Chapter 1_Figure_9_one point perspective projection
Figure 9: One point perspective projection
Chapter 1_Figure_10_two point perspective projection
Figure 10: Two point perspective projection
Chapter 1_Figure_11_three point perspective projection
Figure 11: Three point perspective projection

3.0 Objectives of technical drawing

The general objectives of studying technical drawing include the following:

  • to develop skills in using universally accepted tools, symbols, scales and conventions to draw any visible object or invisible idea on paper, and computer.
  • to understand orthographic and isometric projections and employ it in drafting/drawing ideas and objects using both projections, respectively.
  • to understand and interpret technical drawings, sketches, and working drawings.
  • to develop the ability to use imagination to observe, visualize and draft objects, ideas or concepts.
  • to develop the ability to produce clean, accurate, neat, and informative drawings in a moderate amount of time.
  • to develop the ability to take on any projects and draw environmental health science, civil and environmental engineering objects/structures.

4.0 Purpose of technical drawing

To draft and design objects or structures, and assess how they would appear in real life after they are manufactured, fabricated, assembled, constructed or built. For example, houses, septic tanks, drainages, etc., must be designed and assessed before they are built.

5.0 Application of technical drawing

Technical drawings have wide applications in any field in which planning and designing are required, such as architecture, manufacturing, engineering, construction, environment, estate management, etc.

Sanitarians, surveyors, environmental scientists, and civil/environmental engineers use technical drawings to supervise construction of layouts, structures, objects, and boundaries for various types of properties (houses, etc.).

Technical drawings are also used in situations where ideas/designs for objects and structures need to be modified, and different 2-dimensional views need to be assembled into 3-dimensional views.

Generally, technical drawings are used by a variety of professions, including but not limited to:

  • engineers.
  • architects.
  • contractors.
  • inventors.
  • technicians.
  • teachers.
  • etc.

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Author: Ihagh G. T.

A former university lecturer who has a master's degree and writes on motivation and the environment, as they relate to the challenges and environmental issues that humanity has been facing.

107 thoughts on “Definition & types of technical drawing (PDF download available)”

  1. So you studied architectural drawing which is so much related to this? I read civil engineering, and posted this mainly because of the ease this platform provides to gather links to from many parts of the internet and publish posts for students I teach. thanks for visiting, reading and commenting.

    Like

  2. Very concise and accurate description of technical drafting. I’m an Architect who was dragged kicking and screaming into the world of Autocad. Computer-aided drafting is much slower than hand drafting because it demands precision, but it allows revisions to be made more quickly – you can erase an entire set of plans with a click or the button. It’s unfortunate that many CAD drafters don’t know how to draw.
    In the early days of CAD, I’d get mocked: “Oh, look at the old hand drafter who needs an eraser!” but when the server crashed or the power went out, I’d still be working.

    Liked by 2 people

    1. Bunk, I enjoyed every bit of your interesting observation and comment, and must admit that many CAD drafters don’t know how to draw with tools.

      Drawing with tools is more adventurous and entertaining for me than using CAD because I’ve always liked to use freehand and do fine art long before I started technical/engineering drawing. People who rely alot on CAD won’t be able to survive in countries that have unstable power supply like my own country and that of many others.

      Thank you for visiting, reading and commenting—highly appreciated

      Liked by 1 person

        1. I was thinking a webpage would open for me to read, but rather a pdf copy appeared for me to download—titled “Andrew Loomis: Fun-with-a-pencil”…

          I have to admit that it’s an incredible book which can really help people with the basics of drawing, and which they can continue to improve upon and become much better… your grandfather must have been a brilliant artist…I’m just imagining how good you should be at drawing if you absorbed the contents of this type of book when you were a kid…

          Liked by 1 person

  3. Technical drawing class while earning my engineering degree, two years later: AutoCad. I kept the architect scale and the 30-60-90 triangle for years, though…

    Very well explained!

    Liked by 1 person

    1. interesting to meet another former technical drawing student…from your comments, it seems you have more experience using drawing tools (scale rule, 30-60-90 triangle) than autocad…i prefer using tools whenever I decide to exercise my thinking and imagination more.

      Thanks for visiting, reading and commenting.

      Like

    1. Wow! 41 years in drafting and project management? Allan, that’s still a long way for some of us to go; surely, it contains a lot more experience I still need to get.

      Nice to meet a veteran like you here 😄, and thanks for taking time to visit, read and comment.

      Liked by 1 person

  4. Great piece. I’m an electrical engineer in the Silicon Valley and took “mechanical” drawing for a year in junior high school. Have a great day. Forrest 🙂

    Liked by 1 person

    1. I deeply appreciate your remark about the post. It seems what is applicable in your country/region, is also applicable here: we do technical drawing supervised by lecturers who have a background in mechanical engineering. Thanks a lot for visiting, reading and commenting.

      Like

    1. I appreciate your comment regarding the post, and your experience. There are things that I might not be good at as well, like logistics, social sciences, etc. Thanks a lot for visiting and reading.

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    Like

    1. thanks for visiting, and the compliment too… please note that the article was written for people to whom it can be of immense help to, not necessarily for beginners… also there are many beginners (and probably novices) who will still learn alot from it; or at least a thing or two; this depends alot on one’s own effort and understanding…

      Like

    1. please don’t say that about yourself 😄… thank you for your positive and encouraging remark…bend your mind a bit more, and you will get those things done

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    1. thanks for your thoughtful comment…I have an MSc in water resources & environmental engineering, a BSc in civil engineering, and also have well-researched self-prepared lecture notes on technical drawing which I have been using to teach university undergraduate environmental health science students for about five years

      Like

  10. Reminds me of my days as a technical writer for an engineering company. Luckily, I was able to quit after 15 years and take off with my backpack. 14 countries hitchhiked since turning age 60 two year ago and still going! Just hitchhiked to Oaxaca recently!

    Liked by 1 person

    1. for sure, you have so much experience… but saying “luckily, I was able to quit”, makes me feel you either didn’t like the job, or got tired of it…your comment expresses a great lesson: each person should follow their heart, and do things they are passionate about…thanks for commenting and sharing your thoughts

      Liked by 2 people

        1. I can understand where you are coming from…it happens a lot to many people, and could happen to me…but when we reach there, like in your case, we can look elsewhere for continuous inspiration and fulfillment…thank you

          Liked by 2 people

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    1. thanks alot Matthew; I deeply appreciate your inspiring words and thoughtful comment…I agree with you completely; it looks obvious that most technical and engineering drawing writers haven’t written much about the types of technical or engineering drawing as a whole; this is just a personal observation

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