By Helen on May 10, 2013 in Marking & Measuring Woodworking Techniques
Seeing the difference. Metric vs Imperial
Since learning metric measurements in school I’ve always been a user of the millimeter and never questioned its suitability. Richard was also taught metric first but as soon as he was out in to the practical world of work he adopted the use of imperial finding it much more intuitive. If he hadn’t put up an argument every time I presented a drawing in mm I think I would always have called the inch outdated and inferior. It just makes so much more sense to me to divide a measurement in to 10 equal parts; so much more simple to turn it in to a decimal or fraction. But sometimes we have to realize that our loyalty is simply a stubbornness through desire to stick with the familiar and since Richard can be so very persuasive I started to understand where he was coming from.
Despite the UK’s move to the metric system many moons ago it seems that there are great numbers still clinging on to their feet and inches so there has to be something that gives it an edge. Richard has often told me that it’s the centimetre that’s the problem and he’s not the only person I know who finds it a bit puzzling looking at cm’s when taking large measurements. After several years of becoming more familiar with imperial I think I’ve sussed why the cm is deemed by some as the measurement from Hell! It’s about the ratio between the various units in the system.
A centimetre of course is ten times larger than a millimetre and a metre is one hundred times larger than a centimetre. That’s a perfect relationship for simple mathematics but it isn’t very well balanced when visualising it on a tape measure. A centimetre divides up nicely in to small and accurate millimetres but compare a centimetre to a metre and it’s so small it gets lost. To aid this problem we tend to find that tape measures use a visual queue (a bold line or red number) at every ten centimetre interval and some goes as far as to miss any extra emphasis when we come to a metre instead continuing by calling them 100, 200, etc.
Dividing a metre in to ten like this is much more helpful when measuring long distances than seeing hundreds and hundreds of centimetres but this unit doesn’t really exist with its own name. The red ’20’ on the metric side of the tape in the photo is the location of 120cm but looking at it in isolation this isn’t immediately clear and to add to the confusion the same numbers ‘1- 9’ run continuously along the tape.
By contrast imperial units come without the ease of having to only understand your ten times table. A foot is made up of 12 inches and an inch becomes progressively smaller in divisions of 8, 16, 32 & even 64 should you need to go that small. This makes life difficult at the drawing board but just look at the photo to see how much clearer it makes things in the real world of full scale measurements. Long distances can be read simply with the bold and continuous markings of both inch and feet and if accuracy is required every 1/16″ is also noted. Finding 49″ inches or 4′ 1″ on that tape certainly jumps out much clearer and quicker than searching for 1.24m, 124cm or 1240mm.
The relationship between an inch and foot makes heaps more sense than that of a centimetre and metre and yet I would still never give up my metric system when making scale drawings. Perhaps then we will always continue to keep both versions alive as each definitely brings its own strengths for particular applications. It’s a prime example of when one thing is more suited to theory and another to practise. So…what do you use, and why?
So what are your thoughts? Which system do you use?
Let us know in the comments below.