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2.2 Dimensioning

Pre-Technical Studies · Grade 8 · 10 lessons in the design

What this covers

  • Meaning of dimensioning as used in drawing
  • Types of dimensioning: linear, radial, angular and arc
  • Lines used for dimensioning in drawing
  • Forms of dimensioning: parallel, chain and combined
  • Dimensioning given shapes in drawings

What you will be able to do

  • identify the types of dimensioning in drawing
  • draw lines used for dimensioning in drawing
  • dimension given shapes in drawings
  • embrace the importance of dimensioning in drawing

Key questions

“Why is dimensioning applied in drawings?”

Lessons

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  1. Meaning of dimensioning
    40 min · 1 practice tasks · quiz
    What dimensioning is, why sizes must sit on a drawing, and how that answers why dimensioning is applied in Kenyan workshops and classrooms.
  2. Linear dimensioning
    40 min · 1 practice tasks · quiz
    Linear dimensions as straight-line distances on length, width and height, placed outside the outline with extension lines and millimetre figures.
  3. Radial dimensioning
    40 min · 1 practice tasks · quiz
    Sizing circles and arcs from the centre with R for radius or Ø for diameter, without giving both for the same circle.
  4. Angular dimensioning
    40 min · 1 practice tasks · quiz
    Showing the size of an angle in degrees with a dimension arc between two sides, for slopes, chamfers and wedges.
  5. Arc dimensioning
    40 min · 1 practice tasks · quiz
    The fourth type: arc length along a curve, distinct from radius, diameter and the straight chord between the ends.
  6. Lines used for dimensioning
    40 min · 1 practice tasks · quiz
    Drawing the thin extension line, dimension line, arrowheads, figure and leader, and keeping them distinct from thick object outlines.
  7. Parallel dimensioning
    40 min · 1 practice tasks · quiz
    The parallel or datum form: every size measured from one reference edge so errors do not pile along a chain.
  8. Chain dimensioning
    40 min · 1 practice tasks · quiz
    Chain form: sizes placed end to end so overall is the sum, useful for equal bays, with the risk that small errors accumulate.
  9. Combined dimensioning
    40 min · 1 practice tasks · quiz
    Combined form: chain the parts and add a parallel overall (or datum) so the maker can check that the sum is true.
  10. Dimensioning given shapes
    40 min · 1 practice tasks · quiz
    Matching linear, radial and other types to features of a given combined shape, using correct lines and a sensible form, without repeating sizes.
  11. Portfolio and why dimensioning matters
    40 min · 1 practice tasks · quiz
    A second dimensioned drawing for the portfolio, a recap of types, lines and forms, and a clear answer to why dimensioning is applied in daily making.