Engineering drawings: common features

Drawings convey the following critical information: Geometry – the shape of the object; represented as views; how the object will look when it is viewed from various angles, such as front, top, side, etc. Dimensions – the size of the object is captured in accepted units. tolerances – the allowable variations for each dimension. Material – represents what the item is made of. Finish – specifies the surface quality of the item, functional or cosmetic. For example, a mass-marketed product usually requires a much higher surface quality than, say, a component that goes inside industrial machinery. Line styles and types Standard engineering drawing line types A variety of line styles graphically represent physical objects. Types of lines include the following: visible – are continuous lines used to depict edges directly visible from a particular angle. hidden – are short-dashed lines that may be used to represent edges that are not directly visible. center – are alternately long- and short-dashed lines that may be used to represent the axes of circular features. cutting plane – are thin, medium-dashed lines, or thick alternately long- and double short-dashed that may be used to define sections for section views. section – are thin lines in a pattern (pattern determined by the material being "cut" or "sectioned") used to indicate surfaces in section views resulting from "cutting." Section lines are commonly referred to as "cross-hatching." phantom - (not shown) are alternately long- and double short-dashed thin lines used to represent a feature or component that is not part of the specified part or assembly. E.g. billet ends that may be used for testing, or the machined product that is the focus of a tooling drawing. Lines can also be classified by a letter classification in which each line is given a letter. Type A lines show the outline of the feature of an object. They are the thickest lines on a drawing and done with a pencil softer than HB. Type B lines are dimension lines and are used for dimensioning, projecting, extending, or leaders. A harder pencil should be used, such as a 2H. Type C lines are used for breaks when the whole object is not shown. They are freehand drawn and only for short breaks. 2H pencil Type D lines are similar to Type C, except they are zigzagged and only for longer breaks. 2H pencil Type E lines indicate hidden outlines of internal features of an object. They are dotted lines. 2H pencil Type F lines are Type F[typo] lines, except they are used for drawings in electrotechnology. 2H pencil Type G lines are used for centre lines. They are dotted lines, but a long line of 10–20 mm, then a gap, then a small line of 2 mm. 2H pencil Type H lines are the same as Type G, except that every second long line is thicker. They indicate the cutting plane of an object. 2H pencil Type K lines indicate the alternate positions of an object and the line taken by that object. They are drawn with a long line of 10–20 mm, then a small gap, then a small line of 2 mm, then a gap, then another small line. 2H pencil.