A Text Book on Engineering Graphics - Central Board of Secondary ...
A Text Book on Engineering Graphics - Central Board of Secondary ... A Text Book on Engineering Graphics - Central Board of Secondary ...
EXAMPLE 6: Solution: 60° 60° Steps Involved MACHINE DRAWING Draw to scale 1:1, the front view and side view of a hexagonal headed bolt of diameter 30mm, keeping the axis parallel to H.P and V.P. The length of the bolt is 120mm. Refer Fig. 2.12a 0.8d SHANK LENGTH 30° 60° 0.8d 2d+6 FRONT VIEW R =d Fig 2.12a (i) "Start with the view where circles are seen". Here the side view shows the circles representing the shank. So, start with the side view. (ii) Draw a circle of given diameter, d= 30mm (iii) Draw another circle of diameter 0.8d (24mm), which is shown as broken/discontinuous circle. (Broken part is shown in III quadrant) 'This inner broken circle indicates that the thread on the bolt is an external thread'. (iv) Draw another circle of diameter 1.5d+3 mm (48 mm) indicate the chamfering circle. (v) Circumscribe hexagon around the chamfering circle as in Fig. 2.12b using 30°-60° degree set square and minidrafter. (vi) After completing the side view, the front view will be drawn by taking projections. Project the shank diameter (d= 30 mm) from the side view. Draw a rectangle of size 30x120 mm for the shank (120 mm is the length of the shank) d 30 0.8d 24 1.5d+3 1.5d+3 LEFT HAND SIDE VIEW 52 ENGINEERING GRAPHICS 48 Ø 30 2d+6 66 HEXAGONAL BOLT 30º 30º Fig 2.12 b
MACHINE DRAWING (vii) The end of the bolt is rounded and is done with the radius equal to the diameter of the bolt. (R = d = 30mm) (viii) Indicate the threaded portion (by projecting the 0.8d = 24mm circle with "thin continuous lines") at the end of the shank for the length of 2d+6 mm =66mm (ix) Draw the head of the bolt in the front view, by projecting the hexagon from the side view. Size A/C (across corners) will be projected to get the width of the head. Height of the head is taken as 0.8d= 24mm. (x) The three faces of the hexagonal head with chamfering arcs is drawn by any of the appropriate method. (xi) The centers of chamfering arcs for the three faces may be located as shown in the Fig 2.12a Keep in your mind that, on elevation showing "three faces" of the hexagonal head, show the upper corners of the head chamfered. On elevations showing "two faces" of the hexagonal head, show the upper corners square. 2.5.2 SQUARE HEADED BOLT It is also the common form of the bolt and is generally used where the head of the bolt is to be accommodated in a recess. The recess itself is in the form of square in which the head rests having a little clearance. "The square recess prevents the head from rotating" when the nut is screwed on or off. When the square head of the bolt projects outside the parts to be joined, it is provided with a square nut. The dimensions of the square head are as those of the square nut "except the height or thickness" Let us now learn how to draw the views of a square headed bolt. Example 7 : Solution : Draw to scale 1:1 the Front view and Plan of a square head bolt when it axis is perpendicular to H.P. Take the diameter of the bolt as 24mm, and length as 110 mm. Refer Fig 2.14 Fig 2.13 ENGINEERING GRAPHICS 53
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MACHINE DRAWING<br />
(vii) The end <strong>of</strong> the bolt is rounded and is d<strong>on</strong>e with the radius equal to the diameter <strong>of</strong><br />
the bolt. (R = d = 30mm)<br />
(viii) Indicate the threaded porti<strong>on</strong> (by projecting the 0.8d = 24mm circle with "thin<br />
c<strong>on</strong>tinuous lines") at the end <strong>of</strong> the shank for the length <strong>of</strong> 2d+6 mm =66mm<br />
(ix) Draw the head <strong>of</strong> the bolt in the fr<strong>on</strong>t view, by projecting the hexag<strong>on</strong> from the<br />
side view. Size A/C (across corners) will be projected to get the width <strong>of</strong> the head.<br />
Height <strong>of</strong> the head is taken as 0.8d= 24mm.<br />
(x) The three faces <strong>of</strong> the hexag<strong>on</strong>al head with chamfering arcs is drawn by any <strong>of</strong> the<br />
appropriate method.<br />
(xi) The centers <strong>of</strong> chamfering arcs for the three faces may be located as shown in the<br />
Fig 2.12a<br />
Keep in your mind that, <strong>on</strong> elevati<strong>on</strong> showing "three faces" <strong>of</strong> the hexag<strong>on</strong>al head,<br />
show the upper corners <strong>of</strong> the head chamfered. On elevati<strong>on</strong>s showing "two faces"<br />
<strong>of</strong> the hexag<strong>on</strong>al head, show the upper corners square.<br />
2.5.2 SQUARE HEADED BOLT<br />
It is also the comm<strong>on</strong> form <strong>of</strong> the bolt and is<br />
generally used where the head <strong>of</strong> the bolt is to be<br />
accommodated in a recess. The recess itself is in the<br />
form <strong>of</strong> square in which the head rests having a little<br />
clearance. "The square recess prevents the head<br />
from rotating" when the nut is screwed <strong>on</strong> or <strong>of</strong>f.<br />
When the square head <strong>of</strong> the bolt projects outside<br />
the parts to be joined, it is provided with a square<br />
nut. The dimensi<strong>on</strong>s <strong>of</strong> the square head are as those<br />
<strong>of</strong> the square nut "except the height or thickness"<br />
Let us now learn how to draw the views <strong>of</strong> a square<br />
headed bolt.<br />
Example 7 :<br />
Soluti<strong>on</strong> :<br />
Draw to scale 1:1 the Fr<strong>on</strong>t view and Plan <strong>of</strong> a square head bolt when it axis is<br />
perpendicular to H.P. Take the diameter <strong>of</strong> the bolt as 24mm, and length as 110<br />
mm.<br />
Refer Fig 2.14<br />
Fig 2.13<br />
ENGINEERING GRAPHICS 53
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