ASME Y14.2-2008 pdf download.Line Conventions and Lettering.
2.2 Line Spacing Spacing between parallel lines may be exaggerated to a maximum of 3 mm, so there is no fill-in when the drawing is reproduced.
2.3 Visible Lines Visible lines are continuous and shall be used for rep- resenting visible edges or contours of objects (see Figs. 1 and 2).
2.4 Projection Line Projection lines are lines used to indicate the line of sight between two successive orthographic views.
2.5 Hidden Lines Hidden lines are used to represent hidden edges and contours. They consist of short evenly spaced dashes and are used to show the hidden features of an object (see Figs. 1 and 2). The length of the dashes may vary slightly in relation to the scale of the view. Hidden lines should begin and end with a dash in contact with the visible or hidden line from which they start or end, except when such a dash would form a continuation of a visible line or when a CAD system has limitations that cannot comply with these requirements. Dashes should join at corners, and arcs should start with dashes at tangent points (see Fig. 3). When features located behind transparent materials are depicted, they shall be treated as concealed features and shown with hidden lines. Hidden lines should be omitted when their use is not required for the clarity of the drawing.
2.6.2 Direction and Spacing. Section lines should be drawn at a 45 deg angle within the view [see Fig. 4, item (a)]. On adjacent parts, the section lines should be drawn in the opposite direction [see Fig. 4, item (b)]. For additional adjacent parts, any suitable angle may be used to make each part stand out separately and clearly [see Fig. 4, item (c)]. A suitable angle should be chosen to avoid section lines that are parallel or perpen- dicular to visible lines (see Fig. 5). Section lines shall not meet at common boundaries. Section lines shall be uniformly spaced a minimum of 1.5 mm, and spaced as generously as possible and yet preserve the unity and contrast ofthe sectioned areas (see Fig. 6). Outline section lines are drawn adjacent to the bound- aries only of the sectioned area, and are preferred for large areas when section lines are required, provided clarity is not sacrificed (see Fig. 7).
2.8 Symmetry Line Symmetry lines are used to identify a plane ofsymme- try. The plane of symmetry is identified by placing two short parallel lines (symmetry lines), drawn at right angles, crossing a center line near each end and outside the boundary of the part (see Fig. 1).ASME Y14.2 pdf download.