H L Part 11: Sizing it Up Dimensioning the Drawing

Objectives Of This Lesson Briefly explain why dimensions are needed and their value. Recall the three most basic reasons to keep in mind when applying dimensions. Learn the various methods of applying dimensions. Discuss the components that make up dimension variables.

Overview Dimensions are added to show the size, shape, and location of features on an object, product, buildings, floor plans, etc. Creating dimensions becomes extremely important. If the geometric objects in the drawing are created accurately enough, then the dimensions can be automatically created by the CAD system.

Overview – Important Issues First, Be aware of the dimensioning standard. The choices are ANSI or ISO. The ANSI standard shows the dimension in the middle of the dimension line. The ISO standard has the dimension above an unbroken dimension line.

Overview – Important Issues (cont.) Second, One needs to be aware of the number of decimal places shown in the drawing. This is the number of digits shown after the decimal point, and it implies a degree of accuracy. NOTE: This accuracy varies according to the conditions. If surveying the digits may be 0.0. But in manufacturing a part it could be as precise as 0.000.

dimension updates automatically Overview – Important Issues (cont.) Lastly, dimensions can have associativity, a term that was invented by CAD software vendors to indicate that one drawing can have a relationship to other objects. Stretched object, dimension updates automatically Associative dimensions adjust to changes in the geometric objects that they measure. 8’-0” 4’-0”

Elements in Dimensioning Some dimensioning terms you should know: Dimension lines Extension lines Terminators And Dimension Text

Fig. 11.0 Dimension variables Elements in Dimensioning (cont.) Fig. 11.0 Dimension variables Dimension Line

Fig. 11.0 Dimension variables Elements in Dimensioning (cont.) Fig. 11.0 Dimension variables Extension lines

Elements in Dimensioning (cont.) Fig. 11.0 Dimension variables Terminators (Can be arrows or ticks symbols)

Fig. 11.0 Dimension variables Elements in Dimensioning (cont.) Fig. 11.0 Dimension variables Dimension Text

Methods of Dimensioning There are basic methods used to dimension various objects, structures, architectural plans, etc. Linear Angular Radial, Diameter/Radius Leaders Annotations

Methods of Dimensioning (cont.) Linear Linear dimensions can be horizontal, vertical, or aligned. With aligned dimensions, the dimension line is parallel to the line (imaginary or real) between the extension line origins. Baseline (or parallel) and continued (or chain) dimensions are series of consecutive dimensions that are based on a linear dimension.

Baseline (or parallel) Methods of Dimensioning (cont.) Linear Baseline (or parallel) Continued (or chain Series of consecutive dimensions that are based on a linear dimension.

Series of horizontal and vertical linear dimensions Methods of Dimensioning (cont.) Series of horizontal and vertical linear dimensions

Methods of Dimensioning (cont.) Angular Angular dimensions measures the angle between two lines or three points. To measure the angle between two radii of a circle, you select the circle and specify the angle endpoints. With other objects, you select the objects and then specify the dimension location.

Series of angular dimensions Methods of Dimensioning (cont.) Series of angular dimensions Angular

Series of radial dimensions Methods of Dimensioning (cont.) Series of radial dimensions Radial Radial dimensions measure the radii and diameters of arcs and circles with optional centerlines or a center mark.

Methods of Dimensioning (cont.) Leaders Top plane Front Right plane You can create a leader line from any point or feature in a drawing and control its appearance as you draw. Leaders can be straight line segments or smooth spline curves. Types of Leaders

Methods of Dimensioning (cont.) Annotations Annotation objects include dimensions, notes, and other types of explanatory symbols or objects commonly used to add information to your drawing. Annotation objects provide information about a feature, such as the height/length of a wall. The diameter of a bolt, or the specifications of a product, i.e.. Materials, quantity, color, etc.

Examples of annotated drawings / objects Annotations Examples of annotated drawings / objects H L

Part 12: What We Found, What We Have - Obtaining Drawing Information The preceding was just a general overview to make one familiar with what's involved in understanding and using CAD Up Next: Part 12: What We Found, What We Have - Obtaining Drawing Information