Saturday, 12 February 2011

Engineering Drawing : The Drawing Instruments

What is Engineering Drawing? We can say it as a two dimensional representation of three dimensional objects, which oftenly provides information of its shape, size, material, manufacturing process, etc. It is also well known as a graphic language from which a trained person can visualise objects.

Drawing practice need to follow certain rules. There are some rules and standards. The most common is the International Standards, another standards are ANSI of America, BS of Britain, and DIN of Germany.

Now here are the drawing instruments.

Drawing Board
Drawing boards are usually made of well seasoned softwood of about 25 mm thick with a woorking edge for T-square. The standard size of a board depends on the size of drawing sheet required.

Mini Draughter
Mini draughter is a tool used for drawing horizontal, vertical and inclined lines, perpendicular lines, and for measuring lines and angles. It consists of an angle formed by two arms which rigidly hinged to each other.
Mini Draughter

Scales are tools made of wood, plastic, or steel, used to make drawing of the objects to proportionate size desired.

French Curves
There are more than one shape of french curves. To use them, a series of points are plotted along the desired path, and then the most suitable curve is made along the edge of the curve. A flexible curve consists of a lead bar inside rubbers which could bends conveniently to draw a smooth curve through any set of points.
French Curves

Templates are used to draw small features (circles, triangular, arcs, square, etc.) and symbols used in various science and engineering fields

Pencils are available in different degrees of hardness. The hardness (or the softness you may say) of the lead is indicated as 3H, 2H, H, HB, B, 2B, 3B, etc. The hardness increases as the value of the numeral befor the letter H increases and softer as the value of the numeral before B increases. So the HB denotes a medium hardness leads.
Besides the wooden pencils, there are also mechanical pencils. We can save the sharpening time by using these pencils. The size of the lead diameter are indicated by the number written as 0.50 or 0.70.

 Taken from : Textbook of Engineering Drawing (BS Publications)

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