JNTU
JNTU B.Tech III METROLOGY AND MACHINE TOOLS Previous Question Paper (September - 2021 - R16)
Answer any five questions
All questions carry equal marks
Main
A carbide-cutting tool lasted for 150 min while machining M.S at 35 m/min. If a similar tool is used at 30% higher speed to machine M.S. Calculate the tool life. Also calculate the value of cutting speed if the tool is to machine for 2 hours. Assume n=0.3 in Taylors tool life equation
Answer
Using Taylor's tool life equation, V1T1n = V2T2n = C, where n = 0.3.
Given:
V1 = 35 m/min
T1 = 150 min
n = 0.3
First, calculate the constant C:
For the first part, the new speed V2 is 30% higher than V1:
Calculate the new tool life T2:
For the second part, calculate the cutting speed V3 for a tool life T3 = 2 hours = 120 min:
How is tool life defined? Explain the factors affecting tool life.
Answer
Tool life is defined as the duration of actual cutting time for which a tool can perform its function effectively before it reaches a predetermined failure criterion, such as a specific amount of flank wear, crater wear, or complete tool failure. It is typically measured in minutes.
The factors affecting tool life include:
- Cutting Speed: The most significant factor; increasing speed exponentially decreases tool life due to higher temperatures at the tool-chip interface.
- Feed and Depth of Cut: Higher feed rates and depths of cut increase the cutting forces and heat generation, leading to faster tool wear.
- Tool Material: The hardness, hot hardness, and thermal conductivity of the tool material (e.g., HSS, carbide, ceramic) dictate its resistance to wear.
- Workpiece Material: Harder, tougher, or abrasive materials accelerate tool wear.
- Cutting Fluids: Proper application of coolants and lubricants reduces temperature and friction, significantly extending tool life.
- Tool Geometry: Parameters such as rake angle, clearance angle, and nose radius influence the heat dissipation and stress distribution on the tool.
What are the factors influencing in selection of cutting speeds and feeds for machining operation?
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Give the comparison between drilling and boring machining processes.
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Sketch the work holding devices used in drilling machine and explain the functions.
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Differentiate between shaping, planning and slotting machines based on the operations.
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Explain the Straddle milling and Gang milling operations.
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What are the types of Fits? Explain them with suitable examples.
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What is surface grinding? Explain the working principle of surface grinder.
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Explain in detail about centerless grinding process.
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With reference to the metrology, define and distinguish between the terms:
- Precision and Accuracy
- Repeatability and Reproducibility
- Nominal size and allowance
- Tolerance limits and Control limits
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Discuss various applications of Coordinate Measuring Machine (CMM).
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What are different methods used for tool alignment test? Explain them.
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