GENERAL TERMS

(In accordance with ASME Y14.5 – 2018)

Dimension [3.25]: is a numerical value(s) or mathematical expression in appropriate units of measure used to define the shape, size, orientation or location of a part feature or between part features. 

Tolerance [3.62]: is the total amount that a specific dimension or feature is permitted to vary. It is the difference between the maximum and minimum limit. 

Nominal Size [3.59]: is the designation used for the purpose of general identification. Limit Tolerance Dimensioning: is where a dimension has its maximum and minimum limit stated. In limit dimensioning, the maximum value is placed on the top and minimum value is placed on the bottom. 

Directly Toleranced Dimension [3.27]: is a dimension with an associated plus / minus general tolerance or limit dimension value. 

Bilateral Tolerance [3.63]: is a tolerance in which variation is permitted in both directions from the specified dimension or true profile. 

Equal Bilateral Tolerance [3.63.1]: is a tolerance in which variation is permitted equally in both directions from the specified dimension or true profile. 

Unequal Bilateral Tolerance [3.63.2]: is a tolerance that permits unequal amounts of variation in both directions from the specified dimension or true profile. 

Unilateral Tolerance [3.65]: is a tolerance in which variation is permitted in one direction from the specified dimension or true profile. 

Basic Dimension [3.26]: is a numerical value used to describe the theoretically exact size, true profile, true position or orientation of a feature or a feature of size 

Reference Dimension [3.28]: is a dimension used for information purposes only. It is a repeat dimension or is derived from other values shown on the drawing or on related drawings. 

Geometric Tolerance [3.64]: is a tolerance indicated using a geometric characteristic symbol.

1. Dimension 

2. Nominal Size 

3. Plus/ Minus Tolerance 

4. Limit Size 

5. Equal Bilateral Tolerance 

6. Unequal Bilateral Tolerance 

7. Unilateral Tolerance 

8. Basic Dimension 

9. Reference Dimension 

10. Geometric Tolerance

Single Limit Toleranced Dimension [5.5]: MIN or MAX shall be placed after a dimension when other elements of the design determine the other specified limit. Where MIN is Specified, the upper limit of the dimension may approach infinity. Where MAX is specified, the lower limit of the dimension is zero or defined by other dimensions. Examples of where single limit tolerance dimensions may be used include depths of holes, lengths of threads, corner radii and chamfers. 

 Directly Toleranced Radius [5.16.1]: When a radius symbol R is specified, a tolerance zone bounded by two arcs is created (minimum and maximum radii). The part surface shall be within this zone. When the center of the radius is located via dimensions, the arcs are concentric. When the center of the radius is not located via dimensions, the arcs are tangent to the adjacent surfaces and create a crescent shaped tolerance zone.

Controlled Radius Tolerance [5.16.2]: When a controlled radius CR is specified, a tolerance zone bounded by two arcs is created (the minimum and maximum radii). The part surface shall be within this tolerance zonce and shall be a fair curve without flats or reversals.

Dimension Origin [5.7]: In certain cases, it is necessary to indicate that a dimension between two features shall originate from one of the two features and not the other. One method that may be used to accomplish this is to apply the dimension origin symbol. Where the dimension origin symbol is applied, the high points of the surface indicated as the origin define a plane for measurement.