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Textbook of Engineering Drawing Second Edition by Okay. Venkata Reddy
It’s the graphic language from which a skilled individual can visualise objects. Drawings ready in a single nation could also be utilised in every other nation irrespective of the language spoken. Therefore, engineering drawing is known as the common language of engineers. Any language to be communicative, ought to comply with sure guidelines in order that it conveys the identical which means to each one. Equally, drawing apply should comply with sure guidelines, whether it is to function a method of communication. For this function, Bureau of Indian Requirements (BIS) tailored the Worldwide Requirements on code of apply for drawing. The opposite international requirements are: DIN of Germany, BS of Britain and ANSI of America. The flexibility to learn drawing is a very powerful requirement of all technical folks in any career.
As in comparison with verbal or written description, this methodology is temporary and extra clear. Some of the functions are : constructing drawing for civil engineers, machine drawing for mechanical engineers, circuit diagrams for electrical and electronics engineers, pc graphics for every body. Till not too long ago drawing boards used are made of effectively seasoned softwood of about 25 mm thick with a working edge for T-square. These days mini-draughters are used as an alternative of T-squares which could be mounted on any board. The usual measurement of board relies on the dimensions of drawing sheet measurement required.
Mini-draughter consists of an angle shaped by two arms with scales marked and rigidly hinged to one another (Fig. I. I ). It combines the features ofT-square, set-squares, scales and protractor. It’s used for drawing horizontal, vertical and inclined strains, parallel and perpendicular strains and for measuring strains and angles. Instrument field comprises 1. Compasses, 2. Dividers and 3. Inking pens. What’s essential is the place of the pencil lead with respect to the tip of the compass. It ought to be atleast I mm above as proven in Fig. 1.2 as a result of the tip goes into the board for grip by 1 mm.
Scales are used to make drawing of the objects to proportionate measurement desired. These are made of wooden, metal or plastic (Fig.I.3). BIS recommends eight set-scales in plastic/cardboard with designations MI, M2 and so forth as proven in Desk 1.1 Set of scales . Don’t use the scales as a straight edge for drawing straight strains. These are used for drawing irregular curved strains, aside from circles or arcs of circles. French curves can be found in several shapes (Fig. 1.4). First a sequence of factors are plotted alongside the specified path after which essentially the most appropriate curve is made alongside the sting of the curve.
A versatile curve consists of a lead bar inside rubber which bends conveniently to attract a clean curve via any set of factors. These are aids used for drawing small options akin to circles, arcs, triangular, sq. and different shapes and symbols utilized in varied science and engineering fields (Fig.l.5). Pencils with leads of completely different levels of hardness or grades can be found out there. The hardness or softness of the lead is indicated by 3H, 2H, H, HB, B, 2B, 3B, and so forth. The grade HB denotes medium hardness oflead used for basic function. The hardness will increase as the worth of the numeral earlier than the letter H will increase. The lead turns into softer, as the worth of the numeral earlier than B will increase (Fig.l.6).
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