Inventors, engineers and architects use technical drawings to create master plans or blueprints that are used as working guides to completing projects. A February 2008 article in Smithsonian Magazine suggests that elementary technical drawings scratched into the walls were used by the architect who created the Parthenon at Athens, Greece.
Draftsmen create technical drawings using a tilting table. Parallel rulers on each side of the drawing surface align the drawing paper and provide horizontal and vertical guides for drawing.
Rulers and Squares
Using a T-square and clear plastic triangle, draftsmen create lines. Common triangles they use are an eight inch triangle with forty five and ninety degree sides and a ten inch triangle with 30- and 60-degree sides. Draftsmen measure dimensions with triangular shaped rulers that have different scales on each of three surfaces.
Curve Templates and Compasses
Draftsmen create curves using irregular curve templates made of clear rigid plastic. They draw circles and portions of circles called arcs with an adjustable compass and calculate angles from 1 degree to 180 degrees with clear plastic protractors.
Lettering templates guide the draftsman in the execution of uniform lettering throughout the drawing. As a matter of common practice most creators of technical drawings hand letter in personally developed styles that identify their work as clearly as fingerprints.
Most draftsmen use sharp 2H and 4H pencils for drawing. Pencils may be wooden or mechanical pencils with replaceable leads. They utilize erasing shields and soft gum or nylon erasers to make corrections.
Technical drawings created in pencil are usually over-traced with ink to render durable final drawings. Early inking pens consisted of a mechanical device with an adjustable nib. Modern disposable inking pens have built in ink reservoirs and are available in many point widths.
Early drafting machines date back to Italy in 1913. Modern drafting machines combine horizontal and vertical rulers or scales and a protractor head that allows adjustment of the rulers to required angles for drawing. The device is permanently attached to the drawing board and uses a pair of connected arms to move freely around the drawing surface.
CAD: Computer Aided Design
Drawings and designs using computer software drastically reduce hand and machine drafting, especially in the professional sectors. Lower drawing cost and greater degrees of accuracy dictate increasing use of CAD as a primary tool for creating technical drawings. Large computer screens for creating designs and plotters for printing large technical drawings are replacing traditional technical drawing tools. Colleges and trade schools offer CAD training to a growing number of specializing technicians who are replacing conventional draftsmen in the drafting room.