view A, is the preferred method of drawingdimension lines in many forms of drafting.However, for construction drawings, it ispermissible, and in fact customary, to drawdimension lines from one extension line to anotherwithout breaking them. The numerals are thenplaced above the dimension line and parallel tothe direction of measurement. This method iseasier and saves considerable time.2. Dimension lines are to be aligned ifpractical and grouped for uniform appearance,as shown in figure 10-4, view B. The spacebetween the first dimension line and the objectline should be not less than 10 mm, minimum;the space between succeeding parallel dimensionlines should be not less than 6 mm, minimum, asshown in figure 10-4, view C. Where there areseveral parallel dimension lines, you may staggerthe numerals for easier reading.When using U.S. standards, you should ensurethat the minimum space between the first dimen-sion line and the object line is 3/8 in., and thesucceeding parallel dimension lines are spaced atleast 1/4 in. apart.3. An angle is to be dimensioned with an arcdrawn so that its center is at the apex of the angleand the arrowheads terminate at the extension ofthe two sides, as shown in figure 10-3.4. Crossing dimension lines should be avoidedinsofar as possible. If crossing them is un-avoidable, dimension lines are to be unbroken.Figure 3-23,chapter 3, shows the characteristicsof dimension lines.As explained in chapter 3, extension lines (alsocalled projection lines) are used to indicate theextension of a surface or point to a locationoutside the outline of the object (or view). Theyare usually drawn perpendicular to dimensionlines. Where space is limited, you may drawextension lines at an oblique angle. Figure 10-5,view A, clearly shows this application. You shouldalso minimize the crossing of extension lines overone another and over dimension lines by placingthe shortest dimension line closest to the outlineof the object, as shown in figure 10-5, view B.Where extension lines cross arrowheads or dimen-sion lines close to arrowheads (fig. 10-5, view C),a break in the extension line is advisable. Forexamples in the proper use of extension lines, referto chapter 3,figures 3-30 and 3-31. LEADERS(or leader lines), also explained in chapter 3, directdimensions, notes, or symbols to the intendedplace on the drawing.Figure 10-5.-Applications of extension lines: A. Wherespace is limited; B. Minimizing crossing of extensionlines; C. Where extension lines break.10-8
Integrated Publishing, Inc. - A (SDVOSB) Service Disabled Veteran Owned Small Business