Mechanical Drawing Board & CAD Techniques

Written by jennifer holmes
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  • Introduction

    Mechanical Drawing Board & CAD Techniques

    Before computers, architectural designers and engineers completed all their projects using a mechanical drawing board and tools made to specifically accomplish diagrams and drawings, based on precise measurements. Using the manual tools as a beginner is one of the best ways to learn the basics of technical design and to gain a complete understanding of precise technical diagramming, before moving on to the Auto CAD software of choice. The most important concept of technical drawing, or drafting, is the precise mathematical outlay of the diagram to be reproduced in actuality.

    Old-fashioned mechanical drawing board. (Hemera Technologies/ Images)

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    The Drawing Board

    The mechanical drawing board or drafting table is the common working surface for drafting engineers, architectural designers and other technical professionals. The drafting board has an adjustable bar system underneath the table that allows the table to be adjusted at different resting angles, making it easier to draw on different sections of the drawing. Using a wrist rest bar, which rolls over the drawing without touching the paper directly, helps make drawing easier without making contact on the drawing, which could smear a section of the work. Basic tools for all drafting professionals consist of different size rulers with different scale measures, drawing templates, pencils with different size leads, pens with interchangeable nibs, black ink, adjustable protractor, kneaded erasers, ruling pen, French curve templates and drafting paper. Have plain paper for experimenting with your tools on different types of drawings.

    Modern drafting table. (Hemera Technologies/ Images)

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    Types of Drawing Views

    The isometric, orthographic and oblique views are three ways of drawing mechanical forms, which show objects in varying measurements and perspective. Isometric drawings show the object drawn with edges at equal lengths but looking at the object from an upper right hand corner. Orthographic looks at the object from the front but offset from the centre. Oblique drawing will show the object in a more perspective angle showing distance by measurement reduction from front end to back, but slightly offset. Using your rulers in different measurement scale sizes allows you to professionally create precise lines, particularly where perspective is the main value.

    Different types of templates. (BananaStock/BananaStock/Getty Images)

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    Size Matters

    Precise measures within a drawing are most important as the reproduction of the design is based on precision. If even 1/8-inch off, that can change the dynamics of a new product so that it does not work when it is built. Kitchen and bath designers, working first with a manual drawing and then transferring to a computer program, must account for every 1/4 inch in the design, so the installers know exactly what will be required for the job. The order for cabinets, appliances and other components, such as fillers, are calculated to 1/8 inch, so using computer programs, built for precise measures, are most valuable in showing where there are possible discrepancies. It can be enough of a problem to change out a cabinet to a smaller size and add a cut-down filler to accommodate the difference.

    Computer-generated design plan. (Jupiterimages/ Images)

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    When a product is being developed for the first time, such as an aeroplane engine, the basic drawing will show the outside version of the product. Then the drawing is exploded by magnifying sections of the engine to show the parts involved to make it work. Those parts, in turn, are also exploded to show the internal workings so that every component is shown as a working part of the whole. It is also the point where problems can show up and be solved before the actual building of the part, thus saving lots of money trying to correct a mistake after the job is done. Computer-aided drawing (CAD) is a great timesaver as everything can be done in the software, saving on materials and providing precision that manual drawing may not be able to do. However, learning CAD techniques the manual way first, greatly assist in transitioning to the computer and software programming and learning curve.

    CAD software on the go. (Jupiterimages/Pixland/Getty Images)

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