Imperial or Metric?

I mentioned in a reply to another post yesterday that either system is accurate. I prefer imperial because it’s my base knowledge. When I see Metric, I have to convert it to imperial for it to make sense to me. My wife grew up in Europe and she is just the opposite. Of course we don’t get into the discussions about which is better.. 🙂

Considering a lot of instruction for woodworking is in imperial, I’ve gottem used to it and prefer it for woodworking. My training in engineering has led me to metric, but a lot of old timer engineers will still talk in kips and psf’s. Sometimes imperial units are more intuitive or visual as to metric which reads too cold from eye to mind. If that makea sense.

I can tell or visualize 1/4.1/8 or 1/16 or relate to the human body measures of 36″ 24″ etc that I doubt reading plans in metric will impart to me.

That said it’s also good to ne adaptable to both and know a few key conversions. Like I know 3/8 is 10mm automatically, and fractions of either are easy to figure in the head. There are others of course and not just in lengths. Another convenient mind ‘sticky’ for example, and useful to say, shellac cuts and mixing, is a quart is almost a liter, or 3.78L makes a gallon.

Growing up in the U.S., and having imperial as my primary measurement system …

I prefer imperial, but I think I could almost as easily do my work in metric. I imagine Paul talks imperial in so many of his videos because he did a stint of quite a few years in the U.S. before moving back to the U.K.

Interestingly, I’ve found that I don’t look for my 1/2″ chisel when I want to do my dovetails or mortises. Instead, I look for the biggest chisel that is not larger than the work I’m using it on. In fact, my chisels don’t have size markings on them at all. The only time I care about measurement is when I’m sizing my wood; it really doesn’t matter if it’s 10in or 25cm.

Both systems work fine if I’m following metric plans, I just pull out the metric rule. But while metric aficionados think imperial is backwards, it actually is pretty clever in one important respect. In almost any scale, us customary units have more factors to divide into evenly than metric does.
Ten has two factors to divide evenly, two and five.

The us foot has six factors to the inch level- 1-2-3-4-6. You only have to divide the inch in half to gain 8 as a factor. And if you need other even divisors, just grab a framing square. It has the inch divided by Eights, tenths, twelfths (aka lines), and sixteenths.

If you feel the only proper thing to divide something by is 10, go out and buy an engineer’s or architects rule. They use decimal division of the inch.

The one thing that always makes me smile is the idea that metric is more accurate than the US customary unit. Little known is that in 1893 the US DEFINED the inch as 25.4 mm – exactly. So 10” is exactly 254mm .( see? Decimal). See if your rules agree.

The inch remained the standard measure in the USA until 1959 ( see: international foot and pound agreement.) when we switched to the foot, and defined that as EXACTLY 304.8 mm, which has, miracle of miracles, 16 factors. So you can work with the foot and still be metric, and gain the advantage of many factors.

I believe that is one of the reasons that carpenters even in metric system use some kind of foot is the ease of the mathematics of it. Canadians I worked with always use the foot, though they are a metric country on the hole. I have a Danish rule I was given by a friend from Denmark. It uses a different size foot and inch, but it’s not metric. Europeans might not like the foot because there we so many different feet befor 1799. Belgium, a country I could still easily bike across in a day, had at least 7 different size feet. Germany had several dozen different sizes.

I’ll leave you with two last thoughts:

There are actually two size feet defined in the USA, the US Customary foot, and the Survey foot( defined as 1200/3937 meters) , which reflects the old British size. ( I believe it was Queen Anne’s definition) the survey foot remains so they don’t have to redraw all the surveys. Each state gets to decide which foot to use. If you put the two feet side by side, you can’t tell them apart, surveyors tell me a single plot could be measured by either unit with the same result.

And the British imperial foot is different
than the US customary foot. It is defined by 1/3 the distance between two scratch marks on a bar(aka the yard), just like the meter used to be. It turns out to be 304.798966667 mm to the foot.
So now you see why we use 304.8 mm as the standard.
I wonder which Starret and Stanley used for product they sold in the UK?

Class dismissed.

Think about why the mile is 5280 feet instead of the old Roman 5000 ft.( hint: it was under Elizabeth I just after the Spanish Armada)

Larry Geib,

Nice little lesson! And yes, I’ll take you up on that ft/mile lesson, too! 😛

“Of course, the best thing is to not measure at all.”
That is the way I have been working most of the time.

The US customary system is incoherent in my view, and measures in inches and foot is only the easiest part of it.
The US customary system doesn’t exist by itself as every unit is defined by applying a factor to a SI unit.

For those interested, there is now, since the 29th of May 2019, a new definition of the kilogramme .
One doesn’t have anymore to calibrate his kilogramme standard by comparison to to the physical artefact held in France. That was the latest unit which was based on an artifact.
US citizen can be proud of the NIST contributions to the definitions of the SI units.

https://www.bipm.org/en/worldwide-metrology/

It means transferring dimensions rather than measuring, when possible. If you have an opening and need to fit something into it, for example, you don’t need to know a measurement. Just hold what you are fitting into the opening and mark the dimension. There are many times I will grab a scrap of paper, hold it up to the work, transfer a couple of tick marks, and then carry those over to something else for comparison or for layout. If you have a full scale drawing or story stick, you can mark right from them, too.