Jawaharlal Nehru Technological University Hyderabad
Jawaharlal Nehru Technological University Hyderabad B.Tech II Year MACHINE DRAWING AND COMPUTER AIDED GRAPHICS Previous Question Paper (May - 2019 - R13)
Answer any THREE questions from Part-A. Part-B is Compulsory.
Part-A
Sketch the following machine parts, with proportions marked: Profile of Buttress thread for a nominal diameter of 25 mm and pitch 3 mm, Machine screw of 10 mm diameter, Hexagonal tap bolt.
Answer
The following machine parts are sketched based on standard proportions:
1. Buttress Thread (Nominal Diameter 25 mm, Pitch 3 mm): The thread profile consists of one flank perpendicular to the axis and the other inclined at 45 degrees. The depth of the thread is 0.75P (2.25 mm), and the root and crest are rounded or flat depending on the specific standard. The pressure flank is vertical, while the trailing flank is at 45 degrees to the axis.
2. Machine Screw (10 mm Diameter): A standard machine screw of 10 mm diameter typically features a cheese head or countersunk head. The head diameter is approximately 1.6d (16 mm) and the head height is 0.6d (6 mm). The shank length is determined by the application, with a thread length calculated as 2d + 6 mm.
3. Hexagonal Tap Bolt: A hexagonal tap bolt is fully threaded up to the head. For a nominal diameter (d) of 10 mm, the width across flats (s) is 1.732d (approx. 17 mm) and the head height (k) is 0.7d (7 mm). The bolt features a chamfer of 30 degrees on the top edges of the hexagonal head to facilitate assembly.
Sketch two views of a cotter joint with a gib to connect two square rods of side 30 mm with proper dimensioning.
Answer
A cotter joint with a gib is used to connect two square rods. For square rods of side 30 mm, the following proportions are typically used: width of the cotter at the center = 30 mm, thickness of the cotter = 8 mm, and the gib width is designed to match the cotter taper. The joint consists of a socket end, a spigot end, a cotter, and a gib.
The two views required are the longitudinal sectional view and the side view (or cross-sectional view).
1. Longitudinal Sectional View: This view shows the two square rods (30 mm x 30 mm) joined together. The socket end encompasses the spigot end. The cotter and gib are inserted through the rectangular slot cut through both rods. The cotter is tapered (usually 1 in 24) to allow for tightening, while the gib provides a flat bearing surface to prevent wear on the rod edges.
2. Side View: This view shows the square profile of the rods (30 mm x 30 mm) and the rectangular cross-section of the cotter and gib assembly passing through the center of the rods. The outer dimensions of the socket are typically 1.5 to 2 times the rod side.
Key dimensions for the drawing: Rod side = 30 mm, Slot width = 30 mm, Cotter thickness = 8 mm, and the total length of the joint assembly should be clearly indicated with extension lines. Ensure the taper of the cotter is represented by a slight inclination relative to the vertical axis of the slot.
Draw (a) half sectional view from the front, top half in section and (b) half sectional view from the side, left half in section, of a split-muff coupling, indicating proportions to connect two shafts, each of diameter 50 mm.
Answer
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Sketch a suitable pipe joint to connect two pipes, each of diameter 250 mm. The pipes are to be laid underground. Indicate proportionate dimensions of various parts of the joint.
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Part-B
The Figure shows part drawings of a Flange Coupling. Draw its assembly drawing. All dimensions are in mm.
Answer
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