JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD
JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY HYDERABAD B.Tech II Year MACHINE DRAWING Previous Question Paper (November/December - 2020 - R13)
Answer any TWO questions from Part-A. Part-B is Compulsory.
Part-A
Give the conventional representation of common materials.
Answer
In engineering drawing, conventional representations are used to identify different materials in a sectional view. These symbols are standardized to ensure clarity and uniformity across technical documentation.
| Material | Representation |
| Metals (General) | Parallel lines at 45 degrees, spaced uniformly. |
| Steel | Pairs of parallel lines at 45 degrees, with wider spacing between pairs. |
| Cast Iron | Parallel lines at 45 degrees, with every third line being shorter or thicker. |
| Aluminum and Alloys | Alternating lines at 45 degrees, often with specific hatch patterns. |
| Copper and Alloys | Pairs of lines at 45 degrees, with the second line of each pair being shorter. |
| Lead, Zinc, Tin, White Metal | Double-cross hatching (lines at 45 degrees in both directions). |
| Glass | Parallel lines at 45 degrees with varying spacing or specific dot-dash patterns. |
| Concrete | Small triangles and dots representing aggregate and sand. |
| Wood (Longitudinal) | Wavy lines representing grain structure. |
| Wood (Cross-section) | Concentric rings or irregular circles representing tree growth rings. |
| Earth | Small dots and short dashes arranged in clusters. |
| Water, Liquids | Horizontal wavy lines. |
These conventions allow for the identification of material properties without requiring extensive notes on the drawing, facilitating efficient manufacturing and assembly processes.
Draw the front, top, side views of a hexagonal bolt of diameter 25mm.
Answer
For a hexagonal bolt with a nominal diameter (d) of 25 mm, the standard proportions are used to determine the dimensions for the drawing:
- Nominal diameter (d) = 25 mm
- Bolt head height (H) = 0.7d = 17.5 mm
- Width across flats (W) = 1.732d = 43.3 mm
- Width across corners (D) = 2d = 50 mm
- Chamfer angle = 30 degrees
The views are constructed as follows:
- Front View: Draw the rectangular shank of diameter 25 mm and length as required. The head is drawn as a rectangle of height 17.5 mm and width 43.3 mm. The chamfer on the top face of the head is represented by three vertical lines, where the central face is wider than the two side faces.
- Top View: Draw a regular hexagon with a width across corners of 50 mm. A circle of diameter 25 mm is drawn at the center to represent the shank, and a larger concentric circle representing the chamfer circle is drawn with a diameter equal to the width across flats (43.3 mm).
- Side View: This view is identical to the front view in this orientation, showing the head profile and the shank extension.
All lines should be drawn using standard engineering drawing conventions for fasteners, ensuring the chamfer curves are approximated by circular arcs or straight lines as per standard practice.
Draw the sectional front view, top view of double riveted zigzag lap joint to join plates of thickness 25mm.
Answer
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Draw the sectional front, top and side view of a socket and spigot joint to join two pipes of diameter 30mm each.
Answer
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Part-B
Draw the half sectional front view of the following assembled views of the screw jack.
Answer
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