When any new or improved type of tool, fixture, or machine is being developed, its general arrangement and the principles governing its operation and use may be quite clear in the mind of the inventor or designer, and they may proceed with the actual work of construction, guided only by some mental picture of the mechanism. There are a lot of simple tools or appliances that can be produced in this way, but its evident that such a method is very limited. It is often easier for the designer of a new type of gizmo to build it with his own two hands than to attempt a verbal description to give someone else a clear enough idea of the device so they can build it.
This direct method of construction is totally impractical when applied to regular manufacturing. First off, it would be impossible to create many of the more complicated parts by simply forming a mental picture of them. The basic idea of the device and maybe its general arrangement might be entirely clear, but in order to figure out the exact relation of the various array of parts when they are all properly proportioned and assembled, it is necessary to make an accurate drawing. Such a drawing not only shows the arrangement of the mechanism as a whole, but assists the designer in a big way in the development of the idea as a whole. Quite often, the mental picture is distorted, but when an accurate drawing is made, it is clear as a bell that changes are necessary either in the form and size of one or more of the parts or possibly in the entire make-up of the mechanism.
The General Use of Drawings
The method usually followed by inventors and designers in creating new or improved machines or fixtures is the making of a drawing of whatever idea is being developed. When this has been done, a clear concept of the form and the practicality of the mechanism shown by the drawing may be gotten by the originator of the idea and by other folks who understand drawings and are able to read them. Drawings then serve several important purposes. The first is that they assist in the development of a plan by allowing the inventor or designer to see clearly the relation of different parts to one another and whether or not the planned motion or effect may be obtained. The second is that drawings make it possible for the originator of a plan to convey the idea to others with more ease that if they tried to describe it using mere words. And third, they show those who are actually constructing the device the proportions of its various parts and their relation when they are properly assembled together. And finally, drawings are handy as a hay rake as records of what has been completed and makes it possible to reproduce whatever tool or gizmo is shown on the drawing or drawings.
The Work of the Drafter or Draftsman.
On manufacturing different kinds of mechanical tools and equipment, the work performed can be divided into four different categories:
1. Originating entirely or in part the general type of device to be constructed and the principle governing its operation;
2. Designing the mechanism in according to established mechanical principles and in such a way that the different parts will be strong enough to resist any stresses that they may be subjected to;
3. Making drawings that are needed in the actual work of construction;
4. Making, fitting, and assembling the various parts.
In the study of mechanical drawing, it is totally necessary that you understand the relation of these four categories to one another, because a drafter may simply make drawings according to the ideas of others or they may have more or less to do with originating the plan. The drafter, none the less, is still an integral part of any design or manufacturing process.
Some drafters are able to determine the proportions of different parts and many of them control the process of manufacturing. The designer may be an inventor or vice versa, and he is always a drafter and is capable of making mechanical drawings. The drafter however, is not necessarily a designer and may know little or nothing about the principles governing the design of the part, machinery or tools drawn.
My name is Tim Davis and I teach drafting at http://101info.org.
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