ASME Y14.2:2008 pdf free download – Line Conventions and Lettering
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.
Two widths of lines should be used on drawings (see Fig. 1). The thin line width shall be 0.3 mm minimum. The thick line width shall be 0.6 mm minimum. These approximate line widths are intended to differentiate between thick and thin lines and are not values for con- trol of acceptance or rejection of drawings. All lines of the same type shall be uniform throughout the drawing. The ratio of line widths should be approximately two- to-one (2:1).
2.6 Section Lines Section lines are used to show surfaces cutby a cutting plane. They are drawn as a pattern of straight, equally spaced, parallel lines used to indicate the cut surfaces of an object in section views (see Figs. 1 and 2).
2.6.1 General Principles. Cut surfaces of sectional views may be identified by using section lines. Section lines are optional and may be used when necessary to distinguish individual components of an assembly or to distinguish different surface levels of a full or partial section through a part (see ASME Y14.3M). Lettering should not be placed in section areas. How- ever when it is unavoidable, the section lines shall be omitted in the area for the lettering (see Fig. 4).
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).