JNTU
JNTU B.Tech III ENGINEERING METROLOGY Previous Question Paper (May/June - 2019 - R13)
Note: This question paper contains two parts A and B. Part A is compulsory which carries 25 marks. Answer all questions in Part A. Part B consists of 5 Units. Answer any one full question from each unit. Each question carries 10 marks and may have a, b, c as sub questions.
Part A
(25 Marks)
State the difference between tolerance and allowance
Answer
Tolerance is the permissible variation in the size of a workpiece. It is the difference between the maximum and minimum permissible limits of a size. Allowance is the intentional difference between the sizes of two mating parts, prescribed to achieve a specific type of fit. It is the difference between the maximum limit of a hole and the minimum limit of a shaft (for clearance fit) or the minimum limit of a hole and the maximum limit of a shaft (for interference fit).
With neat sketch, explain shaft basis system in brief.
Answer
In the shaft basis system, the shaft is considered as the basic size, and the holes are varied to obtain the desired fit. The basic size is the nominal size of the shaft. The limits of the hole are determined by the allowance required for the fit, while the limits of the shaft are kept constant. This system is generally preferred when a variety of fits are required for a common shaft size, as it simplifies tooling and inventory.
Sketch:
Imagine a hole and a shaft. In the shaft basis system, the shaft's nominal size is fixed. The hole's size is then adjusted (varied) to create different fits (clearance, transition, interference) with this fixed shaft. For example, for a clearance fit, the hole would be larger than the shaft; for an interference fit, the hole would be smaller.
What are the considerations while manufacturing the slip gauges?
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With an example explain GO and NOGO gauges.
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How straight edge can be used to measure the straightness?
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Describe what are the care to be taken while using optical flat?
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What are the reasons for controlling the surface texture?
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What do you mean by Ra and Rz values? Explain
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How the mechanical comparator is used?
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Name the alignment tests to be performed on milling. Describe any one.
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Unit I
Explain briefly the difference between the interchangeable manufacturing and selective assembly.
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With neat sketch explain the tolerance system in detail.
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In manufacturing system Hole basis or Shaft basis systems which process is preferable and explain why.
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Draw the conventional diagram of limits and fits and explain all the terms in brief.
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Unit II
Give complete classification of gauges with the help of neat diagram.
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What are the essential considerations in selecting the materials for gauges?
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Determine the tolerance on hole and shaft for a precision running fit designed by 40H7/g6, 40 mm lies in the diameter step of 30-50 mm. I = 0.45(D)1/3 +0.001D Microns, fundamental deviation of the shaft = -2.5 D0.34. For hole (H), IT 7 = 16i and for shaft IT 6 = 10i. State the actual maximum and minimum size of the both hole and shaft and maximum and minimum clearance.
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Explain the uses of limit gauges in mass production.
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Unit III
Explain the construction and working principle of Tool makers microscope with neat sketch
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By using optical flat and monochromic light, explain the procedure to determine whether the given surface is flat or curved.
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Name the various types of interferometers. Why monochromatic light is used for interferometry?
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With neat sketch, explain the construction and working of optical projector and state their applications.
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Unit IV
Explain the working of profilograph surface roughness instrument.
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What are the inspection methods used for measurement of surface finish?
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Explain what are the symbols used to indicate the direction of lay along with neat sketch.
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The surface finish on the milled surface with 1.2 mm machining allowance having Ra value 6.3 micro meters with cut off length 2.5 mm and direction of lay parallel. How will you represent it?
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Unit V
Describe the method of measurement of minor diameter of internal threads.
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Write short notes on preparation of acceptance charts for machine tool alignment tests.
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State different types of CMM and explain any one in detail.
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Explain the construction and working of sigma comparator.
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