7.3 Tolerances Answer Key

Question: Explain tolerance
Answer: The acceptable amount of dimensional variation that will still allow an object to function correctly
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Question: What can affect functionality
Answer: Large tolerances
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Question: What can affect costs
Answer: Small tolerances (requires precise manufacturing and quality control with inspection and rejection of parts)
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Question: Which standard requires each dimension have a tolerance, except those dimensions specifically identified as reference, maximum, minimum, or stock. The tolerance may be applied directly to the dimension or indicated by a general note located in the title block of the drawing
Answer: ANSI/ASME Standard Y14.5
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Question: Name the three basic tolerances used most often on working drawings
Answer: 1) limit dimensions; 2) bilateral tolerance; 3) unilateral tolerance
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Question: Describe a limit dimension
Answer: A dimension that provides an upper limit and lower limit for the dimension
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Question: Describe a bilateral tolerance
Answer: A dimension that provides an equal allowable variation, larger and smaller, using a plus/minus (±) symbol to specify the allowable variation
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Question: Describe a unilateral tolerance
Answer: A dimension that provides an allowable variation in only one direction (either larger or smaller) using separate plus (+) and minus (-) signs
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Question: Define Specified Dimension
Answer: Target dimension from which the limits are calculated
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Question: Define Limits
Answer: The maximum and minimum sizes shown by the toleranced dimension
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Question: Define the Upper limit
Answer: The maximum allowable dimension
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Question: Define the Lower limit
Answer: The minimum allowable dimension
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Question: How do you calculate tolerance?
Answer: Subtract the lower limit from the upper limit
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Question: Define General tolerances
Answer: Tolerances that are assumed if no specific tolerance is given for a dimension
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Question: Describe a part that is out of tolerance
Answer: A part that is not within specified limits
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Question: Name the three types of fit
Answer: 1) Clearance Fit; 2) Interference Fit; and 3) Transition fit
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Question: Describe clearance fit
Answer: Limits the size of mating parts so that a clearance always results when mating parts are assembled
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Question: Decribe interference fit
Answer: Limits the size of mating parts so that an interference always results when mating parts are assembled
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Question: Describe transition fit
Answer: Occurs when two mating parts can sometimes have a clearance fit and sometimes have an interference fit
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Question: What is the condition of a part when it contains the largest amount of material?
Answer: Maximum material condition (MMC)
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Question: What is the MMC of an external feature?
Answer: The upper limit of the dimension
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Question: What is the MMC of an internal feature?
Answer: The lower limit of the dimension
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Question: What is the condition of a part when it contains the smallest amount of material?
Answer: Least material condition (LMC)
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Question: What is the LMC of an external feature?
Answer: The lower limit of the dimension
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Question: What is the LMC of an internal feature?
Answer: The upper limit of the diameter dimension
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Question: What is the minimum clearance or maximum interference between parts
Answer: Allowance
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Question: How do you calculate allowance?
Answer: Subtract the MMC of the external feature from the MMC of the internal feature
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Question: What should you do when dimensioning in order to minimize manufacturing cost?
Answer: Specify dimensions only to the precision and tolerance necessary for the part to function properly
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