Antique Drafting Tools

With the advent of Computer Aided Drawing (CAD) programs and computer workstations, the job of draftsman changed dramatically. Before the new technology entered the workplace, everything was done by hand using an array of different tools. After CAD was introduced, all of these tools became obsolete curiosities. All that was needed to create an engineering drawing was a computer terminal and an engineering plotter printer.

Before CAD, drawings were, in fact, drawn rather than printed. The draftsman applied pencil or, in most cases, pen to paper and drew. To make straight lines, the draftsman used a T-Square which slid up and down along the edge of the drawing table. If they needed a vertical line, then they could place a triangle against the T-square as a guide. Later, drafting machines were invented and allowed vertical , horizontal and angled lines to be drawn using a system of pulleys to keep the instrument parallel to the bottom edge of the drawing surface.

Straight lines were easy. To draw curved lines and circles, however, you needed even more tools. Circles were drawn using a compass for larger circles or a circle template for smaller circles. Circle templates were simple pieces of plastic with round holes cut out of them in a variety of sizes. The draftsman would put his pen or pencil on the inside edge of the circle and trace it. A compass held the pen on one leg and a metal point on the other leg. The compass was adjusted to match the radius of the desired circle and the sharp point was place at the desired center point of the circle. The leg with the pen or pencil was then swung around the center point until a full circle had been drawn, usually leaving a small hole at the center point.

If one needed to draw a curve that wasn’t precisely circular, then the dreaded French curves were brought to bear. A French curve was another piece of flat plastic that was carved in such a way that its edges presented a wide variety of different curves. The draftsman would plot on his paper a number of points along the curve required for the drawing and then slide the French curve around until one of its curves touched all of the plotted points and described the desired curve. If the curve was particularly complex, this process might be repeated multiple times for different parts of the curve.

No line was ever drawn freehand on a technical engineering drawing. Freehand was fine for original concept sketches, but could never be trusted to draw the precise curve or perfectly straight line called for on the drawing.

All of that changed when CAD was introduced. CAD made drafting easier, by automatically making lines straight or curved precisely as desired. Snap grids made every line perfect. When a paper copy of the drawing was needed, the file was sent electronically to the large size plotter printer and a paper copy was printed out.

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