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Dimensional Tolerances


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Dimensional Tolerances

  1. 1. Introduction British standards (BS) accepted as national guidelines for industry BS: Defines the standards for technical criteria, manufacturing and health and safety Simplifies and rationalises manufacturing Encourages interchangeability Enables effective communication Dimensional Tolerance
  2. 2. What is a dimensional tolerance? Virtually impossible to achieve exact required size of an item Permissible error = tolerance If the tolerance affects the overall size then it is called a dimensional tolerance Dimensional Tolerance
  3. 3. Factors affecting choice of DT Method of manufacture capability or accuracy of the process Size of item Small things have a smaller tolerance Allowable cost Smaller tolerance is more expensive Dimensional Tolerance
  4. 4. Desired quality Higher quality implies a smaller tolerance Material characteristics Allowable expansion due to temperature variations Interfaces Alignment and fit of a product Standards Specified in various British Standards Dimensional Tolerance
  5. 5. Application of DT’s Can be applied in two ways: 1. General tolerances Applies to all dimensions in drawing Usually shown in the title block Usually applies to non-functional dimensions Dimensional Tolerance
  6. 6. 2. Individual tolerances Tolerance for a particular dimension only Usually for functional (critical) dimensions Individual Tolerance General Tolerance Dimensional Tolerance
  7. 7. Examples of tolerance Individual General Tolerance Tolerance Dimensional Tolerance
  8. 8. F1 - Trolley Housing Dimensional Tolerance
  9. 9. F2 - Hinge Smallest gap: Smallest hole = 15mm Widest pin = 15 - 0.021 = 14.979mm Smallest gap = 0.021 mm Dimensional Tolerance
  10. 10. F3 - Machine Component Dimensional Tolerance