Don't fix it if it's not broken

The inspiration for this week’s instalment of ‘Measure Twice, Cut Once’ came from a picture I saw on LinkedIn. Posted by Mahr, it highlighted the striking similarity in modern technology relating to old designs.

Specifically, the design of micrometers. Since I have never used one, I wouldn’t have known how simple the design actually is, let a lone how old. The image I’m referring to is the one below. Mahr’s post specifically mentioned that they manufactured their first micrometer in 1887 and that they continue to produce these, albeit with a significantly upgraded design, to this day. The biggest difference is instantly visible: the addition of a digital display. In theory this makes the apparatus much more accurate, as well as making it very easy to use. It does give the device a vastly different appearance, though the principles remain the same: the overall shape is still there, somewhat resembling a clamp. The general action of the tool, with a screw handle, is also no different from this older version.

It’s a clear case of “don’t fix it if it’s not broken,” yet it doesn’t stop me from being amazed how little technology sometimes changes when it just works. Looking into the history of the micrometer, what I found to be even more surprising is that it was essentially invented before it was usable. More or less. The word micrometer first enters the English language around 1670, from the Greek micros, meaning small, and metron, meaning measure. This might not seem surprising, but the term originates from before the invention of the metric system, including the micrometre (μm).

Somehow this invention occurred at a time when there was very little use for such extreme precision, yet the first micrometric screw was invented in the 17^th century by William Gascoigne. The diagram to the left here depicts what it looked like.

As with most technologies, the micrometer went through its biggest development during the industrial revolution of the 19^th century, to more or less arrive at the basics of its current design. What’s still interesting though is that until the advent of digitised and automated measuring machines that we are so used to in modern manufacturing, manual micrometers were used in many specialised ways. Sometimes, this meant that special micrometers were made that were very large indeed, such as this depiction from 1908 on the right. It seems almost inviable that such a large measurement was done manually at such precision levels: the variable of human error must have been considerable in this instance.

I feel a little ashamed that this research led me to learn what a vernier scale is. That in itself is nothing to be ashamed about, of course, but I feel like I should have known what it is and how to use it, not only considering the field of work I’m in, but simply as a man who owns a decent pair of callipers. It took me a while to understand how a simple, analogue calliper can measure accurately down to something like 1/20^th of a millimetre, when I previously thought it only showed millimetres. I suppose it’s simply because I’ve never had to measure anything down to that size. A good parallel here, of course is that callipers have had a similar design-trend as micrometers, in that they have barely been altered from their original design and now also often feature a digital display.

For a final thought to see off this instalment, I will leave you with a great video that visualises some fairly common measurement scales in industrial metrology. Unfortunately it’s mostly focused on the imperial system, but 1,000,000:1 scale post-it note that’s visible from space does wonders for helping the brain understand some of the truly abstract levels of measurement that we often deal with.