DOE-HDBK-1016/2-93ENGINEERING FABRICATION, CONSTRUCTION,Engineering Fabrication,AND ARCHITECTURAL DRAWINGSConstruction, and Architectural DrawingsPR-06Page 8Rev. 0When a drawing is dimensioned, each dimension must have a tolerance. In many cases, thetolerance is not stated, but is set to an implied standard. An example is the blueprint for ahouse. The measurements are not usually given stated tolerances, but it is implied that thecarpenter will build the building to the normal tolerances of his trade (1/8-1/4 inch), and thedesign and use of the blueprints allow for this kind of error. Another method of expressingtolerances on a drawing is to state in the title block, or in a note, a global tolerance for allmeasurements on the drawing.The last method is to state the tolerance for a specified dimension with the measurement. Thismethod is usually used in conjunction with one of the other two tolerancing methods. This typeof notation is commonly used for a dimension that requires a higher level of accuracy than theremainder of the drawing. Figure 6 provides several examples of how this type of tolerancingnotation can appear on a drawing.Tolerances are applied to more than just linear dimensions, such as 1 + 0.1 inches. They canapply to any dimension, including the radius, the degree of out-of-round, the allowable out-of-square, the surface condition, or any other parameter that effects the shape and size of theobject. These types of tolerances are called geometric tolerances. Geometric tolerances statethe maximum allowable variation of a form or its position from the perfect geometry impliedon the drawing. The term geometry refers to various forms, such as a plane, a cylinder, a cone,a square, or a hexagon. Theoretically these are perfect forms, but because it is impossible toproduce perfect forms, it may be necessary to specify the amount of variation permitted. Thesetolerances specify either the diameter or the width of a tolerance zone within which a surfaceor the axis of a cylinder or a hole must be if the part is to meet the required accuracy for properfunction and fit. The methods of indicating geometric tolerances by means of geometriccharacteristic symbols are shown in Figure 6. Examples of tolerance symbology are shown inFigure 7.