Drawing Lines, Symbols and Abbreviations

Some of the types of line that are used in most drawings (as laid down in BS 308) is shown below. The lines are designed to ensure that interpretation is clear at all times.

TABLE

The width of the lines, shown in the Table, relates to the width of the nibs of the pens which are used to complete drawings that are produced in design departments or in drawing offices. These widths are only approximate and will change as soon as the drawing is photocopied.

Some drawings may be completed by pencil and then the lines are differentiated by the use of pencils and the leads that possess varying degrees of hardness. So, the softer leads create a blacker line while the fainter lines are drawn using a harder pencil.

The lines that are used for basic dimensioning are depicted using a standard format, which permits commonality between draughtsman and engineer. Dimensions are usually shown so they can be read when the drawing is held on the bottom or right hand edge. This is done to reduce the number of times a drawing is handled and thus potentially increases its working life.

FIGURE

In order to save time and space, abbreviations and symbols (as found in BS 308) can be used when compiling a drawing. Capital letters are normally used to ensure clarity, but lower case letters may be found when it is deemed appropriate. Machining symbols indicate the type of surface finish that a component requires.

FIGURE