08:24 Oct 19, 2016
the point of metric / imperial range is simply in the units used - if you use the metric system, all dimension will tend to be round numbers expressed in the units of the metric system, and similarly when using the imperial system, all dimensions will tend to be whole units or simple fractions of imperial units.
So in the "metric range" of say pipes would be 5mm, 10mm, 13mm 60mm - (just an example, look at any trade catalogue for pipes in metric units for real "standard sizes");
The same way, pipes in the "imperial range" will have different dimensions expressed in round numbers (or simple fractions) in imperial units - the pipes in the "imperial range" would 1/2 inch 3/4 inch, 1 inch diameter etc.
often there is a similar but not equal [slightly larger or smaller] dimension of pipe in the metric and in the imperial range - so there is a temptation to put a pipe dimensioned in whole mm instead of a pipe of nearly same dimensions expressed in round fractions of imperial units, or the opposite - which this clause prohibits. |