TYPES OF SCALES

  1. Plain scale
  2. Diagonal scale
  3. Comparative scale (plain and diagonal type)

REPRESENTATIVE FRACTION (R.F.)

Representative fraction is defi ned as the ratio of the length of an element of the object in the drawing to its actual length.

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Example:

If 1 cm length of the drawing represents 5 m length of the object then in engineering scale it is written as 1 cm = 5 m and in graphical scale it is denoted by:

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DATA REQUIRED FOR CONSTRUCTION OF SCALES

The data required for the construction of a scale are as follows:

  1. R.F. of the scale
  2. The maximum length which the scale can measure
  3. Least count of the scale, i.e. minimum length which the scale can measure. Length of scale is determined by Ls = R.F. × Maximum length

Construction of Plain Scale

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  1. Given (a) R.F. = 1/60 (b) maximum length = 6 m (c) least count = 1 dm
  2. Length of scale, Ls = R.F. × max. length = 1/606100 cm = 10 cm