Relatively accurate

Relatively accurate

Now I know we’ve been banging on long enough about getting accurate dimensions to within 0.25mm or 0.1mm, depending on the context, but one thing we’ve never really discussed is who decides how long a centimetre is, or many centimetres, or a metre?

We’ve long known that the table saw at our workshop (not Rowden’s, I hasten to add) is off by 1mm… sometimes. It’s a quirk of the way the table saw arm is set up. Rather than constantly double checking the saw arm measurement, we simply use one specific long ruler that we can always trust. If the length is over 1 metre we use a tape measure that we trust. And only that one tape measure. It works. We get consistent and reliable measurements, and nothing gets lost in translation.

The long & short of it

Now there’s another situation that can happen, and it will drive even the sanest person round the bend. Most makers have a 15cm, a 30cm, a 60cm and a 100cm ruler. Certainly that is what we recommend at Rowden to all the students. But it isn’t always easy to get all your rulers from the same supplier, and even when they do come from the same supplier it doesn’t mean you’re safe…

It is possible that manufacturing techniques differ between suppliers and between ruler lengths. So it is imperative whenever you buy a ruler that you check it measures the same as the others!

I, for one, would always have assumed that a company whose primary responsibility is to manufacture a length-measuring device might do a bit of its own due diligence to check that their stuff measures accurately! So naive!

As important that they measure the right length, they just have to measure the same distance regardless of which rule you use.

Bet you go and check yours later!

Until next time,



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