How Materials Are Cut Shaped & Formed To A Tolerance (AQA GCSE Design & Technology): Revision Note

Manufacturing to minimum and maximum measurements

• Tolerance is the permitted variation (difference) from a desired measurement

• Manufacturing to a tolerance recognises that:

  • It is difficult and expensive to make every part accurately

  • Some parts can have measurements that are not exactly accurate

• The minimum measurement is the smallest acceptable size

• The maximum measurement is the largest acceptable size

• Any measurement between the minimum and maximum is within “tolerance”

  • A part outside the limits may not fit, work safely or meet the required quality standard

• Tighter tolerances require more accurate equipment and more inspection, which increases cost

Why tolerance is important

• Interchangeability

  • Replacement parts fit without adjustment

• Function

  • Moving parts have enough space but are not loose

• Assembly

  • Holes, slots, tabs and components align

• Safety

  • Parts are not too thin, weak or unsuitable

• Quality and cost

  • The tolerance should be as wide as the product can accept, because increasing precision increases cost