Tolerancing

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Tolerancing
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Tolerance

• Tolerance is the permissible amount that a
  dimension may vary in size and still be useful.
• It is the amount of variation permitted from the
  design specified size and the actual part.

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Tolerance

• Design engineers most often try to make the
  applied tolerance as large as possible and still
  have a useable part.

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Statistical Tolerancing

• The assigning of tolerances to related dimensions
  in an assembly based on the requirements of
  Statistical Process Control (SPC).

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Maximum and Minimum Material Conditions

• The Maximum Material Condition (abbreviated MMC),
  is the condition of a part or feature when it
  contains the most amount of material.
• The Least Material Condition (LMC) is the
  opposite of the MMC. LMC is the least amount of
  material possible in the size of the part.

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Clearance Fit

• A clearance fit is when there is always a
  clearance between mating parts

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Allowance
The Allowance between mating parts is the
tightest possible fit between parts. It is
calculated with the formula MMC Internal
Feature - MMC External Feature Allowance
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Interference Fit

• An Interference Fit, (force fit or shrink
  fit)
• Mating parts must be pressed together.
• Example when a bushing must be pressed into a
  housing or when a pin is pressed into a hole.

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Types of Fits
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Examples of RC Fits Running and Sliding Fits
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Examples of RC Fits Running and Sliding Fits
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Standard RC4 Fits
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Example of Dimensions With Tolerances
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General Tolerances From a Title Block