Unit 9 Dimensioning 181 Copyright Goodheart-Willcox Co., Inc. features, such as holes, Figure 9-16. The chart in this application is sometimes referred to as a hole chart. Running extension and dimension lines to each hole would make the drawing difficult to read. To make the drawing clearer, each hole or fea- ture can be assigned a letter, number, or letter with a subscript number. The dimensions of the feature and its location along the X and Y axes can then be given in a table on the drawing. Coordinate dimensioning without dimension lines is frequently used on drawings containing datum lines or planes, Figure 9-17. This practice Goodheart-Willcox Publisher Figure 9-14. Reference dimensions are marked by parentheses or followed by REF. .495 .495 .568 .568 (2.125) 2.125 REF Older Standard Goodheart-Willcox Publisher Figure 9-15. In tabular dimensioning, a table on the drawing lists the corresponding dimensions for more than one part number. PART NO. A B C D 41–8706 .750 .500 1.312 .875 41–8707 1.125 .750 1.812 1.000 41–8708 1.500 1.000 2.062 1.125 A B D C Goodheart-Willcox Publisher Figure 9-16. A hole chart is a type of tabular dimensioning for a part with a large number of repetitive features, such as holes. −Y +Y .641 .438 2 4 8 6 9 7 10 5 3 1 10 X 10–24 UNF–2B −X +X HOLE NO. 1 2 3 4 5 6 7 8 9 10 DEVIATION X Y +.392 +.523 −.942 +.228 +.567 −.186 −.663 −.383 +.989 −.641 −.188 −1.133 +.790 −1.124 −.992 −1.499 −.449 −1.937 +1.022 −1.406