Geometric shapes are essential elements of technical drawing, as they help to create accurate and clear representations of objects, structures, and systems. In this article, you will learn how to draw some basic geometric shapes with a compass and a ruler, and why they are useful for technical drawing.
To draw geometric shapes, you will need a compass, a ruler, a pencil or pen, and a paper or drawing board. The compass has two legs, one with a sharp point and the other with a pencil or pen, allowing you to draw circles and arcs of different sizes. The ruler is a straight edge with markings for measuring lengths and angles, so you can draw straight lines and measure distances and angles. The paper or drawing board is the surface on which you draw; make sure it is smooth and flat.
The main benefits of using geometric shapes in technical drawing are: 1. Providing a clear, precise, and simplified way to convey essential design information like dimensions, tolerances, and specifications. 2. Enhancing clarity and compatibility with various software and systems, enabling easier sharing and collaboration among designers, engineers, and manufacturers. 3. Facilitating legacy support and comprehensive documentation of design intent throughout the product lifecycle.
A circle is a geometric shape that consists of all points equidistant from a fixed point, known as the center. An arc is a part of a circle, defined by two endpoints and the center. To draw a circle or an arc with a compass and ruler, first adjust the compass to the desired radius, which is the distance from the center to any point on the circle. You can use either the ruler to measure the radius or an existing circle as a reference. Place the sharp point of the compass on the paper where you want the center of the circle or arc to be and press firmly to make a small mark. Rotate the compass around this center, keeping the pencil or pen in contact with the paper until you reach either completion of the circle or your desired endpoint for an arc. If you want to draw an arc with a given angle, use the ruler to mark this angle on paper using the center as vertex, then align your compass with these marks and draw your arc.
Surprisingly organic forms can be achieved simply with only arcs. The Royal Albert Hall (a previous client owned project) cannot possibly have been originally set out with any electronic technology, and although appearing as an ellipse at first glance, is in fact only 4 arcs in plan, formed tangentially. What is easy to set using manual tools is also easy to set out on site, without the need to resort to countless offsets I'm in the lucky position of having be4gun my working life with Rotring pens, dabbled with 3D BIM, then adopted 2D CAD when professional culture wasn't ready for 3D, then migrated to BIM as soon as opportunity allowed. I still value the craft of Rotring pen for subtlety, but not for efficiency of production information
A triangle is a geometric shape that consists of three sides and three angles, whereas a polygon has more than three sides and angles, such as a square, a pentagon, or a hexagon. To draw a triangle or a polygon with a compass and ruler, you should first decide on the length and angle of each side. Then, use the ruler to draw the first side of the triangle or polygon from any point on the paper, marking the endpoints with small dots. After that, adjust the compass to the length of the second side, placing the sharp point of the compass on one of the endpoints, and drawing an arc above or below the first side depending on the desired angle. Repeat this step for each additional side until you reach the starting point of the first side.
An ellipse is a geometric shape that looks like a stretched circle, with two focal points and a major and a minor axis, while an oval is an elongated circle with no focal points or axes. If you want to draw an ellipse or an oval with a compass and a ruler, you must first decide on the length of the major and minor axes. Then, use the ruler to draw the major and minor axes perpendicular to each other and intersecting at the center of the shape. Next, adjust the compass to half of the length of the major axis and draw an arc above or below the minor axis. Repeat this step for the other endpoint of the major axis. Then, adjust the compass to half of the length of the minor axis and draw an arc left or right of the major axis. Finally, draw a smooth curve connecting all four intersection points.
Geometric shapes are beneficial for technical drawing for several reasons. First, they help to create precise and consistent drawings that can be easily reproduced and communicated. Second, they help to simplify complex objects and systems into basic components that can be analyzed and understood. Third, they help to apply mathematical and physical principles to solve problems and design solutions. Fourth, they help to enhance the aesthetic and functional aspects of technical drawing, such as symmetry, balance, proportion, and harmony.
In my experience, using geometric shapes can be very beneficial in technical drawing. In the case of fashion design for example, a geometric shape such as a rectangle can serve as starting block for a design. When I think about it, even a flat pattern often starts out as a geometric shape. A muslin rectangle block for instance is draped and pinned on the dress form to create a garment pattern. Geometric shapes can also be used as guides in technical drawing, for example as a square 3D cube. Geometric shapes can also be used to apply principles like the golden ratio to technical drawings. Using geometry in technical drawing is an overall smart and effective approach to technical drawing.