Re: Conversion One Pound and One Shilling = One Guinea.
"You don't have as much of this in metric but calculations are easier because of the consistency."
Fractions work with decimals, just not as conveniently in some cases. 1/3rd of a metre is a bit imprecise, but half a metre or a quarter metre works fine. Just that almost no one uses them. On the other hand, half a litre is a common usage in speech, but always labelled in print as 0.5l. The usual argument trotted out is "yeah but 12" foot can easily and conveniently be spit into 1/2, 1/3, 1/4, 1/8 etc, etc, etc.". My response is if you are working with those sorts of fractions, then millimetres will get you where you need to be just as easily. You might not be able to convert precisely between, say 1/3rd" and mm, but so what? If you'll be using metric, then you'll measure 8mm because 1/3" isn't what you want. You want something about that size, ie something that will fit into the other part of the same size, ie 8mm. If you need more significant figures, it's just as easy to drill a hole 8.4 or 8.46mm if you need that level of accuracy, but again, there is no need to mix different measuring scales. The only people with problems are those thinking in the old scale and converting in their head to the new scale. All of us above an age have been through that. Some of us still do for some things. I still do my height in feet/inches and my weight in St/lbs (none of this US lbs only malarky!)