Woodwork and mechanical drawing . in salt water. The black lines on the tracinghave protected that part of the paper from the light. When the — 72 — washing is finished the paper is blue with the exception of theplaces where there were lines on the tracing. These linesremain white, thus giving a blue background with white the prints are hung up to dry. As many prints can bemade as desired from the same tracing. 5. Machines are now made to produce blue prints. Theyare lighted by electricity. Sometimes the tracing and paperare fed at one side of the machine and at the other side thepri
Woodwork and mechanical drawing . in salt water. The black lines on the tracinghave protected that part of the paper from the light. When the — 72 — washing is finished the paper is blue with the exception of theplaces where there were lines on the tracing. These linesremain white, thus giving a blue background with white the prints are hung up to dry. As many prints can bemade as desired from the same tracing. 5. Machines are now made to produce blue prints. Theyare lighted by electricity. Sometimes the tracing and paperare fed at one side of the machine and at the other side theprint, all finished and ready for use, is produced in about twoor three minutes. GENERAL DIRECTIONS FOR MECHANICAL DRAWING 1. Fasten paper to drawingboard with thumb tacks. 2. See that upper edge of paperis parallel with upper edge of teesquare when head of tee square isheld against left-hand edge ofboard. 3. Parallel lines, horizontal, ver-tical, and diagonal, constitutesimple definite problems. 4. To draw horizontal parallels. ( J c ) I ~) r \ FIG. 150Illustration showing the use of Tee Square in drawing horizontal parallels. — 73 — hold head of tee square againstleft-hand side of drawing board;push it up or down as needed. SeeFigs. 149 and 150. 5. To draw vertical parallelshold tee square as before. Placetriangle so that right angle touchestee square, and move triangle backand forth along tee square asneeded for lines. Figs. 151 and 152. 6. To draw parallels at 45° settee square as before, placing 45° angle of triangle on tee square, and moving triangle back andforth as needed. 7. It would in many cases be impossible or inconvenient todraw all projects full size. For this reason drawings are madeto scale. That is they are made half size, quarter size, eighthsize, etc. In fact any scale will do that fits the convenience ofthe draftsman. The scales generally used are: 6=l-0; 3=
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Photo credit: © The Reading Room / Alamy / Afripics
License: Licensed
Model Released: No
Keywords: ., bo, bookcentury1900, bookdecade1910, booksubjectmechanicaldrawing
