Drafting Conventions

By: Brian Nettleton

This material is based upon work supported by the National Science Foundation under Grant No. 0402616. Any opinions, findings and conclusions or recommendations expressed in this material are those of the author(s)

and do not necessarily reflect the views of the National Science Foundation (NSF).

Drafting ConventionsIn the field of drafting there are many standards a draftsman must follow in order to properly communicate a design to others. A certain line type or symbol can tell the reader what the type of material the design is made of, weather the surface is machined or not, or if a hole is round or square. The following slides contain basic drafting conventions that will enable a designer to adequately communicate a design to others.

Line TypesThere are many types of lines in a drawing. The following are some of the basic ones.

Boarder lines outline the drawing and contain information about the drawing.

Object lines outline the edges of an object.

Hidden lines show important object lines that are not visible.

Center lines show the middle of a round hole or circular object.

Extension lines extend from an object to define a dimension

Dimension lines define the parameters of a dimension.

Line Weight

The different types of lines in a drawing need to have different thicknesses to help the person reading the drawing interpret it. Boarder lines are always the thickest lines. Object lines and Hidden lines represent the edges of the part and are the next size. The other lines are drawn thinner.

DimensionsDimensions are used to show the size of an object. Dimensions are made up of an Extension line and a Dimension line. The Extension lines extend from ends of the line that is being dimensioned . The Dimension line has arrows at the end that point to the Extension line. The Extension line also contains the number that represents the distance between the Extension lines. Circular objects like holes and fillets have a dimension line that points to the center. Circular objects are dimensioned in diameter or radius.

LetteringLettering is an important part of communicating ideas in a drawing or sketch. Lettering is used in dimensions, notes and in the title block of a drawing. All lettering should be in capitals and be consistent in size. When drawing letters, multiple strokes should be used in either a downward or left to right motion.

Standards and BenchmarksStandard 11: Students will develop abilities to apply the design

process.

J. Make two-dimensional and three-dimensional representations of the designed solution.

Standard 17: Students will develop an understanding of and be able to select and use information and communication technologies.

K. The use of symbols, measurements, and drawings promotes clear communication by providing a common language to express ideas.