3Being able to dimension well requires you to develop three different abilities: Learn the technique of dimensioningUnderstand the different line types and techniques used to show dimensionsLearn the placement of dimensionsCan you pick the most logical and practical place to put dimensions with respect to an object?Learn the choice of dimensionsWhich dimensions should you show and which ones should you not show?
4DimensionThe numerical value that defines the size, shape, location, surface texture, or geometric characteristic of a feature.
5Dimension Line Thin, black line (0.5mm graphite) Ends with an arrowheadArrowhead indicates directionand length of a dimensionGap for dimension is usually near the middleDistance from the object line is 3/8”Distance away from other dimension lines is ¼”
6Extension Line Thin, black line (0.5mm graphite) Extends from the point on the drawing that the dimension refers toDrawn at right angles to dimension linesDistance (gap) from object line before the extension line starts is 1/16”Distance that the line extends past the last arrow is 1/8”
7Arrows Drawn free hand Uniform in size and style Do not vary according to size of drawing or length of dimension3 times as long as they are wide1/8” longNarrow and solid
8Lettering Typically centered on the dimension line If dimensions are right above one another they are staggered1/8” tallFractions are a ¼” tall
9Sample Dimensioning Dimension refers to the number. 20112310Largest dimension to the outside.Extension lines may crossLeave enough room between object and dimension lines.
10Group DimensioningDimensions should be placed outside the drawing whenever possibleExtension lines should not cross dimension lines
11Stagger Dimension Text Stagger the dimension text on parallel dimensions
12Unidirectional and Aligned Methods Unidirectional: All dimensions are horizontalAligned: Dimensions are parallel to object lines
13Principles of Good Dimensioning Each feature of an object is only dimensioned onceDimensions should be placed in the most descriptive view of the featureDimension lines should be aligned and grouped when possible