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Download engineering drawing by nd bhatt.ENGINEERING DRAWING BY N. D BHATT
Below is the list of minimum drawing instruments and other drawing materials which every student must possess: 1. Drawing board 2. T-square 3. Drawing instrument box, containing: i Large-size compass with inter-changeable pencil and pen legs ii Lengthening bar iii Small bow compass iv Large-size divider v Small bow divider vi Small bow ink-pen vii Inking pen 5. Scales 6. Protractor 7. French curves 8. Drawing papers 9. Drawing pencils Sand-paper block Eraser Rubber Drawing pins, clips or adhesive tapes Duster Drafting machine We shall now describe each of the above in details with their uses: 2 Engineering [Ch.
Readers are requested to refer Presentation module 1 for Introduction of the subject and various drawing instruments. It is cleated at the back by two battens to prevent warping. One of the edges of the board is used as the working edge, on which the T-square is made to slide. It should, therefore, be perfectly straight.
In some boards, this edge is grooved throughout its length and a perfectly straight ebony edge is fitted inside this groove. This provides a true and more durable guide for the T-square to slide on.
Its selection depends upon the size of the drawing paper to be used. The sizes of drawing boards recommended by the Bureau of Indian Standards IS are tabulated in table For use in schools and colleges, the last two sizes of the drawing boards are more convenient. Large-size boards are used in drawing offices of engineers and engineering firms. The drawing board is placed on the table in front of the student, with its working edge on his left side.
It is more convenient if the table-top is sloping downwards towards the student. If such a table is not available, the necessary slope can be obtained by placing a suitable block of wood under the distant longer edge of the board.
A T-square is made up of hard-quality wood. It consists of two parts - the stock and the blade - joined together at right angles to each other by means of screws and pins. The stock is placed adjoining the working edge of the board and is made to slide on it as and when required.
The blade lies on the surface of the board. Its distant edge which is generally bevelled, is used as the working edge and hence, it should be perfectly straight. The nearer edge of the blade is never used. The length of the blade is selected so as to suit the size of the drawing board. Now-a-days T-square is also available of celluloid or plastic with engraved scale. Drawing Instruments and Their Uses Art. The stock of the T-square is held firmly with the left hand against the working edge of the board, and the line is drawn from left to right as shown in fig.
The pencil should be held slightly inclined in the direction of the line i. Horizontal parallel fines are drawn by sliding the stock to the desired positions.
A pencil must be rotated while drawing lines for uniform wear of lead. The T-square should never be used on edge other than the working edge of the board. It should always be kept on the board even when not in use.
Turn the T-square upside down as shown by dashed lines and with the same edge, draw another line passing through the same two points. If the edge is defective the lines will not coincide. The error should be rectified by planing or sand-papering the defective edge. Those made of transparent celluloid or plastic are commonly used as they retain their shape and accuracy for a longer time.
Two forms of set-squares are in general use. A set-square is triangular in shape with one of the angle as right angle. Vertical lines can be drawn with the T-square and the set-square.
To draw a fine perpendicular to a given horizontal line from a given point within it. The pencil point should always be in contact with the edge of the set-square.
A perpendicular from any given point outside the FIG. Vertical parallel lines may be drawn by sliding the set-square along the edge of the T-square to the required positions. Problem The lines can also be drawn by placing the FIG. A circle can similarly be divided into eight equal parts by lines passing through its centre fig. A circle may be divided into twelve equal divisions in the same manner fig.
A circle may thus be divided into 24 equal parts with the aid of the set-squares fig. To draw a line parallel to a given straight line through a given point. The line AB and the point P are given fig. B ii Place the other set-square as a base for the first. CD is the required parallel line. By keeping the edge of the T-square as base for the set-square, parallel lines, long distances apart, can be drawn. To draw a line perpendicular to a given line through a point within or outside it.
The line PQ and the point Oare given fig. Method J: i Arrange the longest edge of one set-square along PQ. To draw a line parallel to a given straight line al a given distance, say 20 mrn from it fig. D Let AB be the given line. A FIG. It consists of two legs hinged together at its upper end. A pointed needle is fitted at the lower end of one leg, while a pencil lead is inserted at the end of the other leg.
The lower part of the pencil leg is detachable and it can be interchanged with a similar piece containing an inking pen. Both the legs are provided with knee joints. Circles upto about mm diameter can be drawn with the legs of the compass kept straight. For drawing larger circles, both the legs should be bent at the knee joints so that they are perpendicular to the surface of the paper fig. The setting of the pencil-lead relative to the needle, and the shape to which the lead should be ground are shown in fig.
To draw a circle, adjust the opening of the legs of the compass to the required radius. Hold the compass with the thumb and the first two fingers of the right hand and place the needle point lightly on the centre, with the help of the left hand. Bring the pencil point down on the paper and swing the compass about the needle-leg with a twist of the thumb and the two fingers, in clockwise.. The compass should be kept slightly inclined in the direction of its rotation. While drawing concentric circles, beginning should be made with the smallest circle.
The lower part of the pencil leg is detached and the lengthening bar is inserted in its place. The detached part is then fitted at the end of the lengthening bar, thu's increasing the length of the pencil leg fig. It is often necessary to guide the pencil leg with the other hand, while drawing large circles. It is difficult to exert the same amount of pressure on the lead in the compass as on a pencil. It is, therefore, desirable to use slightly softer variety of lead about one grade lower, HB or HJ in the compass than the pencil used for drawing straight lines, to maintain uniform darkness in all the lines.
In most of the instrument boxes, a needle attachment is also provided which can be interchanged with the pencil part of the compass, thus converting it into a divider. The dividers are used: i to divide curved or straight lines into desired number of equal parts, ii to transfer dimensions from one part of the drawing to another part, and iii to set-off given distances from the scale to the drawing.
They are very convenient for setting-off points at equal distances around a given point or along a given line. To divide a straight line into a number of equal parts - say 3. If the last division falls 1 short, increase the set distance by approximately of the difference by means of the nut, keeping the other point of the divider on the paper. If the last division goes beyond the end of the line, decrease the set distance by i of the difference.
With some practice, it will be possible to obtain the desired result with less trials and in short time. The trial divisions should be set-off as lightly as possible so that the paper is not pricked with large and unnecessary holes. Any arc or a circle can similarly be divided into any number of equal divisions.
It consists of a pair of steel nibs fitted to a holder made of metal or ivory. Ink is filled between the two nibs to about 6 mm length by means of a quill which is usually fitted to the cork of the ink bottle. The screw should be on the side, farther from the T-square.
As the ink dries rapidly, the pen should be used immediately after it is filled. The inside faces of the nibs should be frequently cleaned for the ink to flow freely and to maintain uniformity in thickness of lines.
The solutions to exercises of Chapter 17, Isometric Projection and Chapter 20 Conversion of Views are given in this edition. Share B. D Bhatt pdf — Latest Edition to other engineering or diploma students and help them to download Engineering Drawing Book pdf.
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