Dimensioning and Tolerancing Fundamentals
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Questions and Answers

What does Maximum Material Condition (MMC) refer to?

  • The maximum amount of material within the stated limits of size (correct)
  • The average size of a feature
  • A condition where the material is evenly distributed
  • The minimum size of a feature

    • Every feature control frame must contain a reference datum.

    False

    What problem arises with the angularity of a tolerance zone?

    The zone is wedge-shaped, allowing more tolerance at one end than the other.

    The ______ controls the axis-to-axis relationship between two features.

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

    Match the following tolerancing concepts with their definitions:

    <p>Profile of a surface = Controls shape and location of a contour when datums are specified Perpendicularity = Controls orientation relative to a datum Circular runout = 2D control of a surface relative to a datum axis Maximum Material Condition = Contains the maximum amount of material within size limits</p> Signup and view all the answers

    What system do most drawings conform to?

    <p>SI and U.S. Customary</p> Signup and view all the answers

    A zero must always be placed before the decimal point for values less than one inch.

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

    Where do notes typically appear on a drawing?

    <p>lower right-hand corner</p> Signup and view all the answers

    When dimensioning a visible gap, there should be at least ___ ___ between extension lines and object geometry.

    <p>1 mm</p> Signup and view all the answers

    Match the following symbols with their meanings:

    <p>|___| = Counterbore / = Countersink</p> Signup and view all the answers

    What is the minimum distance dimension lines should be from any view?

    <p>10 mm</p> Signup and view all the answers

    A dimension specified for a given feature on one level of drawing is mandatory for that feature at any other level.

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

    All dimensions and tolerances apply in a _____ _____ condition.

    <p>free state</p> Signup and view all the answers

    What is the purpose of baseline dimensioning?

    <p>To eliminate the accumulation of tolerances</p> Signup and view all the answers

    Tolerances specify the total permissible variation in a dimension.

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

    What does ASME stand for?

    <p>American Society of Mechanical Engineers</p> Signup and view all the answers

    A loose running fit is used for __________ commercial tolerances or allowances on external members.

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

    Match the following types of fits with their descriptions:

    <p>Locational Clearance Fits = Provide a snug fit for locating stationary parts Force or Shrink Fit = Maintains constant bore pressures throughout the range of sizes Free Running Fit = Good for large temperature variations and high running speeds Sliding Fit = Intended to move and turn freely while locating accurately</p> Signup and view all the answers

    What is the consequence of using chain dimensioning?

    <p>It can increase the maximum distance between features.</p> Signup and view all the answers

    A dimension should appear multiple times in different views on a drawing.

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

    What does a line with an arrow pointing down on a drawing indicate?

    <p>Specifying depth</p> Signup and view all the answers

    Form tolerances are concerned with individual features and are not related to __________.

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

    Which tolerancing method is most frequently used?

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

    Dimensions and tolerances apply only at the drawing level where they are specified.

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

    How many decimal places should a dimension have based on its tolerance?

    <p>The same number</p> Signup and view all the answers

    The feature control frame contains the geometric characteristic symbol, the geometric tolerance, and the relative __________.

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

    What does the nomenclature 'TYP' signify in engineering drawings?

    <p>The feature is repeated a certain number of times.</p> Signup and view all the answers

    A unilateral tolerance allows deviations in both directions from the basic size.

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

    Direct dimensioning yields the ______ accumulation of tolerances.

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

    What is statistical tolerancing?

    <p>A method of assigning tolerances based on sound statistical practices.</p> Signup and view all the answers

    Which type of fit always ensures space exists between mating parts?

    <p>Clearance Fit</p> Signup and view all the answers

    Match the types of fits with their descriptions:

    <p>RC = Running or sliding clearance fit LC = Locational clearance fits LN = Locational interference fit FN = Force fit</p> Signup and view all the answers

    For metric dimensions, a plus or minus sign is always shown.

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

    Describe what the primary datum plane is established by.

    <p>A minimum three-point contact with the back surface of the object.</p> Signup and view all the answers

    The difference between the maximum material limits of mating parts is referred to as ______.

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

    What does '3 mil' plastic sheet stock refer to?

    <p>3 millimeter thickness</p> Signup and view all the answers

    Errors related to GD&T stem from how the datum reference frame was established.

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

    What happens when the designer does not pay attention to dimensioning?

    <p>They may assign dimensions improperly, like 0.075 ± 0.02.</p> Signup and view all the answers

    A locational interference fit is designed for parts that require ______.

    <p>rigidity and alignment</p> Signup and view all the answers

    Which fit requires the tightest fit usable with cast iron?

    <p>Medium drive fit</p> Signup and view all the answers

    What is the shape of the tolerance zone for angularity?

    <p>Wedge-shaped</p> Signup and view all the answers

    What happens when tolerances are applied that are too large or too loose?

    <p>Parts may function improperly</p> Signup and view all the answers

    What does the profile tolerance control when datums are specified?

    <p>Shape, size, and location of the contour</p> Signup and view all the answers

    Which of the following tolerances does NOT require a reference datum?

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

    Which statement accurately describes the use of basic dimensions in engineering drawings?

    <p>Basic dimensions locate the perfect position of features from identified datums.</p> Signup and view all the answers

    In chain dimensioning, how are features dimensioned?

    <p>Features are dimensioned relative to one another.</p> Signup and view all the answers

    When dimensioning a gap, what is the minimum space that should be maintained between extension lines and object geometry?

    <p>1 mm</p> Signup and view all the answers

    What is the preferred distance that dimension lines should be from any view in a drawing?

    <p>10 mm</p> Signup and view all the answers

    Which of the following systems do most engineering drawings conform to?

    <p>SI; U.S. Customary</p> Signup and view all the answers

    What is indicated by the symbol '|' in a drawing?

    <p>A counterbore</p> Signup and view all the answers

    Which statement is true regarding the use of zeros before decimal points in dimensions?

    <p>A zero is omitted before the decimal point for dimensions less than one inch.</p> Signup and view all the answers

    What is the reasoning behind applying dimensions in a free state condition?

    <p>To apply tolerances in the most favorable conditions</p> Signup and view all the answers

    Baseline dimensioning helps in eliminating what aspect related to tolerances?

    <p>The accumulation of tolerances between two features</p> Signup and view all the answers

    What type of fits allow for a small amount of clearance or interference?

    <p>Locational transition fit</p> Signup and view all the answers

    Which of the following tolerances controls the orientation of a surface or axis relative to a datum?

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

    What framework contains the geometric characteristic symbol, the geometric tolerance, and the relative datums?

    <p>Feature control frame</p> Signup and view all the answers

    Which fits are characterized by maintained constant bore pressures throughout a range of sizes?

    <p>Force or shrink fit</p> Signup and view all the answers

    Which type of fits is not intended to run freely but should allow accurate movement and location?

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

    What does the angulated tolerance control in relation to a datum?

    <p>Orientation of a surface or hole</p> Signup and view all the answers

    What should dimensions on a drawing primarily indicate?

    <p>Only the most critical features</p> Signup and view all the answers

    What does unilateral tolerance imply about deviation from the basic size?

    <p>Deviations are restricted to one direction only.</p> Signup and view all the answers

    What type of fit is best for high running speeds and large temperature variations?

    <p>Free running fit</p> Signup and view all the answers

    Which of the following is true regarding baseline dimensioning?

    <p>It is preferred over chain dimensioning</p> Signup and view all the answers

    Which type of fit is specified to ensure that an interference will always exist between mating parts?

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

    Clearance fits are characterized by which of the following descriptions?

    <p>A space or clearance always exists between mating parts.</p> Signup and view all the answers

    What indicates the diameter when dimensioning circles?

    <p>Diameter symbol</p> Signup and view all the answers

    What is the primary purpose of statistical tolerancing?

    <p>To assign tolerances based on statistical practices.</p> Signup and view all the answers

    What should be the main basis for the number of decimal places in a dimension?

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

    What is the maximum allowable variation in dimensions referred to as?

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

    When dimensioning a part, which of the following is a best practice concerning hole features?

    <p>Dimension hole features as circles where they appear.</p> Signup and view all the answers

    Which fits are primarily used when accurate location is important?

    <p>Locational transition fit</p> Signup and view all the answers

    What does the nomenclature 'TYP' or 'TYPICAL OF' indicate in engineering drawings?

    <p>A feature is standard and repeated.</p> Signup and view all the answers

    For metric dimensions, how is a single zero represented?

    <p>Without a plus or minus sign.</p> Signup and view all the answers

    Which category of fits is known for ensuring accurate location while allowing both clearance and interference?

    <p>Locational Transition Fit</p> Signup and view all the answers

    When dimensioning in inches, how is the tolerance value typically expressed?

    <p>With the same number of decimal places as the basic size.</p> Signup and view all the answers

    What is the difference known as between the maximum material limits of mating parts?

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

    Which fit is characterized by tight assembly and is practical for materials that can be highly stressed?

    <p>Force Fit</p> Signup and view all the answers

    What is the purpose of GD&T in engineering drawings?

    <p>To enable clearer specification of design intent.</p> Signup and view all the answers

    What is a key consideration for establishing the primary datum plane?

    <p>Minimum three-point contact.</p> Signup and view all the answers

    What should be done first when determining an English fit for a design?

    <p>Choose the type of fit required.</p> Signup and view all the answers

    Study Notes

    Dimensioning and Tolerancing Fundamentals

    • Metric vs. US Customary: Drawings use either the SI (metric) or US Customary system.
    • Decimal Representation (mm): Dimensions less than 1 mm use a zero before the decimal; whole millimeters omit the decimal and zero; decimals greater than 1 but less than 2 mm show the non-zero decimal digit.
    • Decimal Representation (inches): A zero is not used before the decimal for values less than 1 inch.
    • Dimension Placement: Dimension lines should be a minimum 10 mm from any view; 6 mm clearance between dimension lines if placed outside other dimensions. At least 1 mm should be between extension lines and object geometry. Dimension lines extend 2–3 mm past the extension lines.
    • Datum References: Basic dimensions, boxed dimensions, denote theoretically exact feature locations from clearly defined datums.
    • Dimensioning Holes/Features: Dimensioning holes from the part end is preferred over dimensioning between holes.
    • Dimensioning Techniques:
      • Chain Dimensioning: Dimensioning features relative to each other (used in situations needing feature relationships).
      • Baseline Dimensioning: Dimensions originate from a common datum to eliminate tolerance accumulation (preferred over chain dimensioning).
      • Dimensioning Location: Dimension only to visible or solid lines.
    • Geometric Tolerancing:
      • Form Tolerances: Control the shape/geometry of individual features (straightness, flatness, circularity, cylindricity).
      • Profile Tolerances: Define a 2D tolerance zone by two contours (controls shape and size/location of contour). Methods exist for inspecting profile tolerances such as optical comparitors and mechanical gaging.
      • Orientation Tolerances: (parallelism, perpendicularity, angularity) Control the orientation of a surface or axis relative to datum.
      • Position Tolerances: Controls the orientation and location of a feature (center, axis, plane) in relation to datum/datums. These are 3D tolerance zones.
      • Symmetry Tolerances: Similar to concentricity, but related to the position of a center plane relative to an axis or datum (harder to inspect).
      • Circular Runout: 2D control; surface relative to a datum axis.
    • Tolerance Types:
      • Bilateral Tolerances: Deviation equally distributed above and below the basic size.
      • Unilateral Tolerances: Deviation in one direction only (above or below).
      • Limit Dimensions: High and low limit tolerances displayed above and below.
      • Statistical Tolerancing: Using statistical methods to assign tolerances based on processes. Has a disadvantage of potentially resulting in more restrictive tolerances.
      • Clearance Fits: Space exists between mating parts.
      • Interference Fits: Interference exists between mating parts.
      • Transition Fits: Either a clearance or interference fit may result.
      • Allowance: Difference in maximum material limits between mating parts.
      • Basic Size: Size from which limit dimensions are derived.
      • Hole Basis (Basic Hole System): Basic size is applied to lower limit of the hole.
      • Shaft Basis (Basic Shaft System): Basic size applied to upper limit of the shaft.
    • Fits:
      • English Fits: (RC, LC, LT, LN, FN). Follow specific procedures to determine tolerances per drawing.
      • Metric Fits: Includes fits for loose running, free running, close running, sliding. Locational clearance, locational transition, locational interference. Fit types for drive (medium drive) and force fit. Follow similar procedures as English Fits.
    • GD&T (Geometric Dimensioning and Tolerancing) Advantages: Allows designers to clearly specify design intent, improve communication, and reduce misinterpretation.
    • Datum Reference Frames: Required for GD&T (datums create references for the feature control frame features)
    • Application Considerations: Tolerances that are too small/tight result in increased manufacturing difficulty and cost. Tolerances that are too large/loose may result in malfunctioning parts.
    • Feature Control Frame: Contains geometric characteristic symbol, geometric tolerance, and relative datums.
    • Other Notes: Tolerances are applied in a free state in an engineering drawing; dimensions have assumed room temperature and pressure contexts; dimensions shall appear only once on a drawing unless otherwise specified; if a dimension has a tolerance, every single dimension must show a tolerance.
    • Dimensioning Practices: Circular features are typically dimensioned as diameters; arcs are usually dimensioned as radii.

    Special Feature Types

    • Chamfers: Dimensioned with length from end and angle or two distances.
    • Depth: Represented by a line with a down-pointing arrow.
    • Gage/Code Materials: Specified by linear dimensions (diameter or thickness).
    • 90° Angles: Implied where centerlines and feature lines are at right angles (basic dimensioning).
    • Maximum Material Condition (MMC): Feature of size with the maximum amount of material within stated size limits.

    Additional Details

    • Geometric Characteristics: Include terms like straightness, flatness, parallelism, perpendicularity, angularity, circularity, cylindricity, concentricity, position, symmetry, profile.
    • Conventional Tolerancing: Controls size only.

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    Description

    This quiz covers the essential principles of dimensioning and tolerancing in engineering drawings, including both metric and US customary systems. It delves into decimal representation, dimension placement, and datum references. Enhance your understanding of key practices in precision engineering design.

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