ADDA Dimensioning Terminology

The size of the part as measured.

The minimum clearance ormaximum interference between two mating parts.

The size from which the limits of sizeare derived by the application of allowances andtolerance.

The space between two mating parts.

A portion of a part, such as a hole, keyway, orflat surface.

The maximum holediameter or minimum shaft diameter. When a partweighs the least.

The maximum and minimumallowable sizes of a feature.

The minimum holediameter or maximum shaft diameter.When the part weighs the most.

A non-toleranced dimensionused for information purposes only. It may not governproduction or inspection.

The total amount by whichthe part dimensions are permitted to vary.

Variation of size in one direction eitherpositive or negative.

Variation of size in both directionspositive and negative.

Stated with dimension in field ofdrawing.

Stated in title block.

Internal Dimension maintains asmaller size than external between mating parts. Fit type: RC –Running and Sliding, LC – Locational Clearance

Internal Dimension maintains alarger size than external between mating parts. Fit type: LT –Transition

Condition where a clearance orinterference fit may be present between mating parts. Fit type:LN – Locational Interference, FN – Force or Shrink

Minimum hole size is used as the basesize for fit tolerance calculations.

Maximum shaft size is used as the basicsize for fit tolerance calculations.