Metric versus Imperial

Yeeeaaaaah!!! It has been long time hasn’t it? Now then, some thoughts on measuring things for a coffee break….


At our recent courses with Chris Schwarz building two kinds of tool chest; Dutch and Anarchic flavoured, it was clear that some people used metric measurements and others used imperial.  Actually, that is fundamentally untrue:  In reality not much was being measured at all (which is sometimes the beauty of working with the dimensions of the stock that you have). But, insofar as anything did actually get measured, I could see the two systems in use. 


It set me thinking about how I approach the craft in terms of measurement. these days my first rule is ‘measure as little as possible’.  But when I do absolutely have to measure something when woodworking I do use both metric and Imperial interchangeably depending on what it is I am measuring. That’s odd because I use the metric system exclusively in my day job as a professional engineer and once, a long time ago (in a galaxy far, far away…) I used to scoff loudly at the ‘crazy’ Imperial system.  That was all brought to an end by a semi-retired engineer who taught me all I know about hogging things out of solid metal (The Black Art…).

I know you are wondering where this is going but stay with me on this…


Each weekend I would cycle to Barrie’s workshop and we would spend Saturday turning and milling solid metal or cutting and bending sheet. Usually this would be making things like fittings for operating theatre lights or dentists light boxes for looking at X-rays.  Invariably he would give me things to do accompanied by metric drawings. One day he gave me  a drawing in imperial and I was, to put it politely, ‘amused’ (probably in truth I was an obnoxious and condescending know it all).  Instead of “taking the ‘ump” at my irksome manner Barrie took it in his stride, made a cup of tea and sat down to tell me a story: At the start of his career in the early 1960s he worked for Hunting Defence, developing missile systems for the British effort in the cold war. At one point he was asked to attend the Paris Airshow where Mikoyan Gurevich (a.k.a MiG, a.k.a ze dastardly Russians) were showing off their latest wonder-jet; the MiG-21. The Russians allowed the Brits to walk around their new fighter, to touch it and even to take pictures but our boys were under a diktat not to measure anything. Production of any sort of measuring device when in the proximity of the aircraft  would mean that serious consequences would ensue.  Why? The Russians knew that if we were able to measure their aircraft that we could gauge its performance. So, what to do?

One of Barrie’s colleagues hit on a neat suggestion.  He pointed out that the length of a typical stride of a six foot man is a yard (3 feet). Taking strides of a metre looks unnatural but a yard looks natural for most around that height. He went on to point out that the same six footer would have an arm span of precisely the same distance, at least one of the British delegation would have shoes that were exactly a foot in length, that the distance from index finger to that heel of your hand is about six inches and that the distance to the first joint of your thumb is about an inch.  The British delegation walked around the aircraft, pacing the perimeter of its wings. they took photos with a hand on a wing, then on the fuselage and a foot next to a wheel. In short they used Imperial dimensions and at the end of it they were able to calculate the MiG21’s wing area, wing thickness, fuselage area, length, width and thereby its gauge performance with a remarkable degree of accuracy.  I stopped laughing at Imperial measurement after that and realised that sometimes using the ‘measure of man’ is the right thing to do.

And here is the curious thing: when I absolutely have to measure something for woodworking, completely unconsciously I find myself dropping into Imperial and have to consciously flip to metric. But, if I am working in metal I use metric and have to consciously flip to Imperial (when dealing with American supplier for example).  Bizarre.  

All of the foregoing is, of course, a long way round of saying that each system has its place. But then I know Peter Follansbee is laughing at me because I have never seen Peter measure anything at all…


– Paul Mayon


3 thoughts on “Metric versus Imperial

  1. My souvenier from York this year is a Metric/imperial tape measure. I know I could get one online but I got one here, partly because I’m a rebel and we work entirely in milimetres, and partly because no-one will ever steal it because it is obviously mine.

    Not sure how we’d do some of the things we do in milimetres though. How do you do shrinkage percentages in milimetres? Maybe if we only had inches we’d not bother making it so complex.

    I bet everything would still work out fine.

    On the other hand, that was a great story so thanks for sharing it. I’ll bear it in mind if I need to measure some sensitive equipment surreptitiously.

  2. My story is similar to yours and I also use metric for metal or very precise woodwork and imperial for all other woodwork. I wonder if it is fundamental to the two systems? Metric is easy to dial up on machines and imperial much easier to divide by two – 1/2″ become 1/4″ etc. Hence for me it is much easier to proportion a piece of wood and as you point out it is all based on the size of the human body so perhaps imperial relates more readily to the relationship between us and the wooden piece. Isometric standards are undoubtably fabulous for engineering and science but it is imperial for wood for me.

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