ADDA Dimensioning Terminology

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ADDA Dimensioning Terminology
2012-06-26 23:55:30
adda dimensioning terminology drafting certification

Study Guide for ADDA Mechanical Drafting Certification
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  1. Actual Size
    The size of the part as measured.
  2. Allowance
    The minimum clearance ormaximum interference between two mating parts.
  3. Basic Size
    The size from which the limits of sizeare derived by the application of allowances andtolerance.
  4. Clearance
    The space between two mating parts.
  5. Feature
    A portion of a part, such as a hole, keyway, orflat surface.
  6. Least Material Condition
    The maximum holediameter or minimum shaft diameter. When a partweighs the least.
  7. Limits
    The maximum and minimumallowable sizes of a feature.
  8. Maximum Material Condition
    The minimum holediameter or maximum shaft diameter.When the part weighs the most.
  9. Reference Dimension
    A non-toleranced dimensionused for information purposes only. It may not governproduction or inspection.
  10. Tolerance
    The total amount by whichthe part dimensions are permitted to vary.
  11. Unilateral Tolerance
    Variation of size in one direction eitherpositive or negative.
  12. Bilateral Tolerance
    Variation of size in both directionspositive and negative.
  13. Specific Tolerance
    Stated with dimension in field ofdrawing.
  14. General Tolerance
    Stated in title block.
  15. Clearance Fit Tolerance
    Internal Dimension maintains asmaller size than external between mating parts. Fit type: RC –Running and Sliding, LC – Locational Clearance
  16. Interference Fit Tolerance
    Internal Dimension maintains alarger size than external between mating parts. Fit type: LT –Transition
  17. Transition Fit Tolerance
    Condition where a clearance orinterference fit may be present between mating parts. Fit type:LN – Locational Interference, FN – Force or Shrink
  18. Basic Hole System
    Minimum hole size is used as the basesize for fit tolerance calculations.
  19. Basic Shaft System
    Maximum shaft size is used as the basicsize for fit tolerance calculations.