Technical Drawing

Technical drawing, also known as drafting or draughting, is the technique of creating accurate representations of objects for architecture and engineering drawings. A skilled practitioner of the art is known as a draftsman or draftsperson (or draughtsman, draughtsperson in the UK). Today the mechanics of the drafting task have been largely automated, and greatly accelerated, through the use of CAD systems. 

Manual drafting The basic mechanics of drafting is to place a piece of paper (or other material) on a smooth surface with right-angle corners and straight sides - typically a drafting table. A sliding straightedge known as a t-square is then placed on one of the sides, allowing it to be slid across the side of the table, and thus over the surface of the paper. 

Parallel lines can be drawn simply by moving the t-square and running a pencil or technical pen along the t-square's edge, but more typically the t-square is used as a tool to hold other devices such as set squares or triangles. In this case the draftsman places one or more triangles of known angles on the t-square - which is itself at right angles to the edge of the table - and can then draw lines at any chosen angle to others on the page.

Modern drafting tables come equipped with a parallel rule that is supported on both sides of the table to slide over a large piece of paper. Because it is secured on both sides, lines drawn along the edge are guaranteed to be parallel.

In addition the draftsman uses several tools to draw curves and circles. Primary among these are the compass, used for drawing simple arcs and circles, and the French curve, typically a piece of plastic with complex curves on it. A spline is a rubber coated articulated metal that can be manually bent to most curves.

This basic drafting system requires an accurate table and constant attention to the positioning of the tools. A common error was to allow the triangles to push the top of the t-square down slightly, thereby throwing off all angles. Even tasks as simple as drawing two angled lines meeting at a point required a number of moves of the t-square and triangles, and in general drafting was a time consuming process.

.A solution to these problems was the introduction of the "drafting machine", an application of the pantograph (sometimes referred to incorrectly as a "pentagraph" in these situations) which allowed the draftsman to have an accurate right angle at any point on the page quite quickly. These machines often included the ability to change the angle, thereby removing the need for the triangles as well. 

In addition to the mechanics of drawing the lines onto a piece of paper, drafting requires an understanding of geometry and the professional skills of the specific designer. At one time, drafting was a sought-after job, considered one of the more demanding and highly-skilled of the trades.

Today the mechanics of the drafting task have been largely automated, and greatly accelerated, through the use of CAD systems. Drafting is often accomplished by the engineer, architect, or machinist. Skilled CAD operators continue to be in demand for routine changes to drawings.

Common views of objects created by draftspeople include: 

• floor plan (or bird's-eye view)
• Orthographic projection
• Axonometric projection
• Isometric projection
• Dimetric projection
• Trimetric projection
• Orthogonal projection
• Oblique projection
• Perspective projection, Perspective (graphical)
• Engineering drawing

For example, a floor plan  in architecture and building engineering is a diagram of a room, a building, or a level (floor) of a building as if seen from the above (i.e., a map). You may also think of it as a "top view" or "bird's eye" view of one floor in a building. Technically, the floor plan shows the walls and fixtures in a building at the height of one meter (or 4'-0") "above the finished floor" (AFF).

The term may be used in general to describe any drawing showing the physical layout of objects. For example, it may denote the arrangement of the displayed objects at an exhibition, or the arrangement of exhibitor booths at a convention. A copy of an original floor plan drawing is traditionally called a blueprint. Now drawings are reproduced using plotters and large format xerographic copiers.

Plan view or "planform" is defined as a vertical orthographic projection of an object on a horizontal plane, like a map.

It is also called a "plan" in architectural terms, as opposed to "elevation" which means how the object will look when seen from a side, or a "cross section" where the building is shown cut along an axis to reveal the interior. A "reflected ceiling plan" shows a view of the room as if looking from above, through the ceiling, at a mirror installed one foot below the ceiling level, which shows the reflected image of the ceiling above. This convention maintains the same orientation of the floor and ceilings plans - looking down from above.