Unit 4: Standard of Measurements
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Questions and Answers

What is the primary limitation of measurements made using traditional methods?

  • Inability to measure complex shapes
  • Lack of precision in measuring instruments
  • Inability to measure small dimensions
  • Dependency on the skill of the operator and being time-consuming (correct)

    • What is the primary cause of characteristic variability in a manufacturing process?

  • Lack of training among operators
  • Improperly adjusted machines, operator error, tool wear, and/or defective raw materials (correct)
  • Random fluctuations in the production process
  • Natural variability in materials

    • What is the purpose of controlling a manufacturing process?

  • To achieve consistent production and meet design requirements (correct)
  • To reduce production costs
  • To improve product quality
  • To increase production volume

    • What is the term used to describe the permissible level of variation in dimension during manufacture?

    <p>Tolerance</p> Signup and view all the answers

    What is the basic or nominal size of a component?

    <p>The size based on which the dimensional deviations are given</p> Signup and view all the answers

    What is the difference between the upper and lower limits of a component's dimension?

    <p>Permissive tolerance</p> Signup and view all the answers

    What is the primary reason why a rule is not suitable for measuring the distance between two edges?

    <p>Because it is a line-measuring device</p> Signup and view all the answers

    What is the main advantage of using end standards over line standards?

    <p>They provide higher accuracy of measurement</p> Signup and view all the answers

    What is the primary cause of undersizing when using line standards?

    <p>Wear on the leading ends of the scale</p> Signup and view all the answers

    What is the minimum dimensional tolerance that can be obtained using end standards?

    <p>±0.0005 mm</p> Signup and view all the answers

    What is the primary reason why a magnifying lens or microscope is required for high-accuracy measurement using line standards?

    <p>To magnify the scale markings</p> Signup and view all the answers

    What is the primary reason why end standards are not subjected to parallax errors?

    <p>Because they rely on the feel of the operator</p> Signup and view all the answers

    What is the primary reason for providing clearance between a shaft and a hole?

    <p>To allow for an oil film to be maintained for lubrication purposes</p> Signup and view all the answers

    What is the consequence of manufacturing parts to exact sizes without considering variations?

    <p>Increased production cost and reduced quality</p> Signup and view all the answers

    What is the principle behind interchangeable manufacture?

    <p>Manufacturing components in bulk to the desired accuracy</p> Signup and view all the answers

    What is the benefit of interchangeable assembly?

    <p>Increased productivity and reduced manufacturing cost</p> Signup and view all the answers

    What is the distribution of dimensions produced in a controlled manufacturing process?

    <p>Normal or Gaussian distribution</p> Signup and view all the answers

    What is the consequence of not considering dimensional variations in manufacturing?

    <p>Reduced product quality and increased cost</p> Signup and view all the answers

    What is the primary purpose of interchangeable manufacture?

    <p>To reduce manufacturing and assembly time and enhance quality</p> Signup and view all the answers

    What is the main reason for providing tolerances in manufacturing?

    <p>To permit dimensional variations in the manufacture of components</p> Signup and view all the answers

    What is universal interchangeability?

    <p>When parts manufactured at different locations are randomly chosen for assembly</p> Signup and view all the answers

    What is the primary advantage of interchangeable assembly?

    <p>Ease of replacement of defective or worn-out parts</p> Signup and view all the answers

    What is the significance of traceability to international standards in universal interchangeability?

    <p>To ensure common standards are followed by all</p> Signup and view all the answers

    What is the definition of tolerance?

    <p>The magnitude of permissible variation of a dimension or other measured value or control criterion from the specified value</p> Signup and view all the answers

    What is the main reason why scientists opted for a natural unit for length?

    <p>To eliminate the effect of environmental conditions on the unit of length</p> Signup and view all the answers

    Which type of standard is defined as the distance between two flat parallel surfaces?

    <p>End standard</p> Signup and view all the answers

    What is the significance of the wavelength of monochromatic light in the measurement of length?

    <p>It remains constant under different environmental conditions</p> Signup and view all the answers

    Why are material standards no longer used as the fundamental unit of linear measurement?

    <p>They can change their size with temperature and other conditions</p> Signup and view all the answers

    What is the difference between a line standard and an end standard?

    <p>A line standard is used to measure distances between lines, while an end standard is used to measure distances between surfaces</p> Signup and view all the answers

    What is the significance of the Act of Parliament in relation to the unit of linear measurement?

    <p>It governed the use of yard and metre as legal line standards</p> Signup and view all the answers

    What is the primary factor that determines the specification of tolerance limits?

    <p>Functional requirements</p> Signup and view all the answers

    What is the difference between the upper and lower limits of a component?

    <p>Tolerance</p> Signup and view all the answers

    What type of fit is used where a permanent or semi-permanent assembly is required?

    <p>Interference fit</p> Signup and view all the answers

    What is the purpose of the ISO system of limits and fits?

    <p>To define the relationship between mating parts</p> Signup and view all the answers

    What is the purpose of a Go gauge?

    <p>To check the lower limit of a part</p> Signup and view all the answers

    What type of gauge is used to check the dimensions of shafts?

    <p>Ring gauge</p> Signup and view all the answers

    What is the purpose of a No-Go plug gauge?

    <p>To check the upper limit of a hole</p> Signup and view all the answers

    What is the primary purpose of gauges in manufacturing?

    <p>To ensure parts fit and function correctly</p> Signup and view all the answers

    What is the primary difference between the Hole Basis System and the Shaft Basis System?

    <p>The basic size of the part</p> Signup and view all the answers

    What is the purpose of limits in manufacturing?

    <p>To ensure parts fit and function correctly</p> Signup and view all the answers

    Study Notes

    Standard of Measurements

    • Two standard systems for linear measurement: English (yard) and metric (metre) systems
    • The metric system is widely accepted and used as the fundamental unit of linear measurement
    • Scientists have always sought a suitable unit for length that remains constant regardless of environmental conditions
    • The wavelength of monochromatic light is used as a natural and invariable unit for length

    Line and End Measurements

    • Line standard: measures distance between two engraved lines
      • Examples: yard and metre
      • Used for quick and easy measurements
      • Limited accuracy (±0.2 mm) and requires magnifying lens or microscope for high accuracy
    • End standard: measures distance between two flat and parallel surfaces
      • Examples: slip gauges, end bars, and micrometer anvils
      • Used for precision measurements in workshops and laboratories
      • High accuracy (up to ±0.0005 mm) and requires skill and time for measurement

    Characteristics of Line Standards

    • Quick and easy measurements
    • Limited accuracy (±0.2 mm)
    • Engraved lines have thickness, making high accuracy measurements difficult
    • Markings on the scale are not subjected to wear, but leading ends may wear, resulting in undersizing
    • No built-in datum, making alignment difficult
    • Subject to parallax effect, leading to reading errors

    Characteristics of End Standards

    • High accuracy (up to ±0.0005 mm)
    • Measurements are time-consuming and require skill
    • Measuring surfaces are subjected to wear
    • Built-in datum, making alignment easy
    • Not subject to parallax error

    Comparison between Line and End Standards

    • Line standards: quick and easy, but limited accuracy and no built-in datum
    • End standards: high accuracy, but time-consuming and requires skill, with a built-in datum

    Limits, Fits, and Tolerances

    • Manufacturing processes inherently produce variations in size and shape
    • Tolerances: the magnitude of permissible variation in a dimension or measured value
      • Upper limit: maximum allowable dimension
      • Lower limit: minimum allowable dimension
      • Tolerance: difference between upper and lower limits
    • Fits: describe the relationship between mating parts, such as a hole and a shaft
      • Clearance fit: gap between mating parts, used for easy assembly and disassembly
      • Interference fit: overlap between mating parts, used for permanent or semi-permanent assembly
      • Transition fit: slight gap or overlap, used for accurate location and moderate tightness

    Principle of Interchangeability

    • Manufacture of identical parts in bulk, allowing for interchangeable assembly
    • Essential for mass production and modern manufacturing techniques
    • Enables the production of components with a desired fit, without further modification during assembly
    • Increases productivity, reduces manufacturing cost, and facilitates ease of replacement

    Tolerances

    • Essential for manufacturing products with a desired level of accuracy and quality
    • Tolerance principles: permit dimensional variations, achieve interchangeable assembly, and ensure functional requirements
    • Tolerance is an absolute value, defined as the algebraic difference between the upper and lower acceptable dimensions
    • Industry follows approved accuracy standards, such as ANSI and ASME, to manufacture different parts### Tolerances
    • A letter indicates the fundamental deviation (position of tolerance zone relative to nominal size)
    • A number indicates the tolerance grade (size of tolerance zone)

    Basis Systems

    • Hole Basis System: hole is kept as basic size, shaft size is varied to get desired fit
    • Shaft Basis System: shaft is kept as basic size, hole size is varied to get desired fit

    Gauges

    • Essential for quality control in manufacturing processes
    • Used to measure dimensions of manufactured parts and ensure conformity to specified limits

    Types of Gauges

    • Limit Gauges:
      • Check whether part's dimension falls within specified limits
      • Go Gauge: checks lower limit, part should fit into or pass through
      • No-Go Gauge: checks upper limit, part should not fit into or pass through

    Plug Gauges

    • Cylindrical gauges used to check dimensions of holes
    • Go Plug Gauge: should fit into hole
    • No-Go Plug Gauge: should not fit into hole

    Ring Gauges

    • Used to check dimensions of shafts
    • Go Ring Gauge: shaft should fit into ring
    • No-Go Ring Gauge: shaft should not fit into ring

    Snap Gauges

    • Used to check external dimensions of cylindrical parts, such as shafts
    • Go Snap Gauge: part should pass through
    • No-Go Snap Gauge: part should not pass through

    Limits and Fits

    • Limits: define permissible variations in dimensions to ensure parts fit and function correctly
    • Fits: describe relationship between mating parts, ensuring correct assembly (clearance, interference, and transition fits)

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    Description

    This quiz covers the standard systems for linear measurement, including the English and metric systems, and the importance of the metric system as the fundamental unit of linear measurement.

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