Sections and sectional views

A section is used to show the detail of a component, or an assembly, on the cutting plane. Cutting planes are indicated on the drawing by a long chain line of 0.35 mm thickness, which is thickened at both ends to 0.7 mm. The cutting plane is lettered and the arrows indicate the direction of viewing. Symmetrical parts may be drawn half in section and half in outside view, and this type of drawing avoids the necessity of introducing dotted lines for the holes and the recess. Many products are manufactured from very thin materials, which are virtually impossible to cross hatch in a sectional view, and in these cases it is usual to make them entirely black. However, if two or more thin sections are adjacent to each other, a gap is left so that the profile of the separate components is clearly defined. Many recognizable components in assembly drawings positioned along the cutting plane such as nuts, bolts, washers, rivets, pins, keys, balls, rollers, spokes of wheels, and similar symmetrical parts are not drawn in section.