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Standard Engineering Drawing Practices

Using standard abbreviations, line types, dimensions, title blocks and symbols ensures that engineering drawings are readily understood. The American Society of Mechanical Engineers (ASME), International Standards Organization (ISO) and British Standards Institute (BSI) have issued standard engineering drawing practice guidelines. The BSI standards are based upon International Standards Organization (ISO) standards. American drawing standards and practices are separate from other international standards.

Geometric Dimensioning and Tolerancing

GD&T is a system for defining and communicating engineering tolerances. It uses a symbolic language on engineering drawings and computer-generated three-dimensional solid models for explicitly describing nominal geometry and its allowable variation. It tells the manufacturing staff and machines what degree of accuracy and precision is needed on each facet of the part.

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.

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