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A hole of 20 mm diameter is to be drilled in a steel block of 40 mm thickness. The drilling is performed at rotational speed of 400 rpm and feed rate of 0.1 mm/rev. The required approach and over run of the drill together, is equal to the radius of drill. The drilling time (in minute) is
[ME 2014,Set-2]
  • a)
    1.00
  • b)
    1.25
  • c)
    1.50
  • d)
    1.75
Correct answer is option 'B'. Can you explain this answer?
Verified Answer
A hole of 20 mm diameter is to be drilled in a steel block of 40 mm th...

L = t + Ap1
Ap= 0.5 D (holes diameter)
= 10 mm
t = 40 mm
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Most Upvoted Answer
A hole of 20 mm diameter is to be drilled in a steel block of 40 mm th...
Given:
- Diameter of the hole to be drilled = 20 mm
- Thickness of the steel block = 40 mm
- Rotational speed of the drill = 400 rpm
- Feed rate = 0.1 mm/rev
- Required approach and overrun of the drill = radius of the drill

To find:
- Drilling time in minutes

Approach:
1. Calculate the distance to be drilled by considering the approach, hole diameter, and overrun.
2. Calculate the number of revolutions required to drill the hole.
3. Calculate the drilling time using the rotational speed and feed rate.

Calculation:
1. Distance to be drilled:
- Approach + Hole diameter + Overrun = 2 * radius
- Approach + 20 mm + Overrun = 10 mm (radius of the drill)
- Approach + Overrun = 10 mm - 20 mm = -10 mm (negative value indicates that the approach and overrun will be subtracted from the total drilling distance)

2. Number of revolutions:
- Distance to be drilled = Thickness of the block + Approach + Overrun
- Distance to be drilled = 40 mm + (-10 mm) = 30 mm
- Number of revolutions = Distance to be drilled / Feed rate
- Number of revolutions = 30 mm / 0.1 mm/rev = 300 rev

3. Drilling time:
- Drilling time = Number of revolutions / Rotational speed
- Drilling time = 300 rev / 400 rpm = 0.75 min = 1.25 minutes

Answer:
The drilling time is 1.25 minutes (option b).
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A hole of 20 mm diameter is to be drilled in a steel block of 40 mm thickness. The drilling is performed at rotational speed of 400 rpm and feed rate of 0.1 mm/rev. The required approach and over run of the drill together, is equal to the radius of drill. The drilling time (in minute) is[ME 2014,Set-2]a)1.00b)1.25c)1.50d)1.75Correct answer is option 'B'. Can you explain this answer?
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A hole of 20 mm diameter is to be drilled in a steel block of 40 mm thickness. The drilling is performed at rotational speed of 400 rpm and feed rate of 0.1 mm/rev. The required approach and over run of the drill together, is equal to the radius of drill. The drilling time (in minute) is[ME 2014,Set-2]a)1.00b)1.25c)1.50d)1.75Correct answer is option 'B'. Can you explain this answer? for Mechanical Engineering 2024 is part of Mechanical Engineering preparation. The Question and answers have been prepared according to the Mechanical Engineering exam syllabus. Information about A hole of 20 mm diameter is to be drilled in a steel block of 40 mm thickness. The drilling is performed at rotational speed of 400 rpm and feed rate of 0.1 mm/rev. The required approach and over run of the drill together, is equal to the radius of drill. The drilling time (in minute) is[ME 2014,Set-2]a)1.00b)1.25c)1.50d)1.75Correct answer is option 'B'. Can you explain this answer? covers all topics & solutions for Mechanical Engineering 2024 Exam. Find important definitions, questions, meanings, examples, exercises and tests below for A hole of 20 mm diameter is to be drilled in a steel block of 40 mm thickness. The drilling is performed at rotational speed of 400 rpm and feed rate of 0.1 mm/rev. The required approach and over run of the drill together, is equal to the radius of drill. The drilling time (in minute) is[ME 2014,Set-2]a)1.00b)1.25c)1.50d)1.75Correct answer is option 'B'. Can you explain this answer?.
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