Why can't we go fully metric? .
Imperial is designed to be used by the man in the street. A bit of 2x2 is a fence post, a pint fits in your hand, a gallon of petrol moves you X miles (no need for the 100 bit in litres per 100 KM). The fractions are meant to be done in your head. For selling nails and buying boiled ham it's superior.
Metric was initially cobbled together so French civil servants didn't need to know how many Breton inches were in a Parisien yard and could tax everyone the same way. It is the superior engineering and science system because the revolutionary tax men in their quest for "reason" turned to the physicists who by 1789 were getting past the evil spirits and seeing what's inside a dog stage. The natural numbers like 10m head of water almost being 1 bar are useful.
IMHO we should use both but define the break. You should be sold a gallon petrol, it's a perfectly good quantity and lets you do the cost calculations. The fact that the half-inch hose on the pump is designated 12.5mm (all rubber hose is still really Imperial, as are tyres, nails....) and the rest of the mechanism was designed in mm is no hassle to the user but helps the engineers. Crossover items like nuts and bolts would be better defined like shoe sizes so the yanks can used them but don't get confused. If everyone uses a number 6 bolt no one cares that it's M6. By having M8 as #7 no fool tries to use M7 without serious effort.
Andy
