By The Metric Maven

Bulldog Edition

It has been brought to my attention that the Discovery Channel has a show called *Gimme Shelter*. It has a person called Mr Short Cut who apparently offers viewers advice on short cut methods for DIY work. In a video: “Mr Short Cut demonstrates the advantages of using the metric system for easy measurements.” Here is what he has to say:

Narrator: Here’s a man who gets eight hours of sleep in five hours. Mr Shortcut.

Mr Shortcut: Hey you remember a few years ago when the big craze the big push was to make everything go metric? Well I gotta tell ya when it comes to carpentry I think they might have been on the right track. Let me show you what I mean. I mean if you have to measure and add some distances with boards for example, just something simple I’ll show ya [Mr Shortcut holds a board and tape measure, he then starts to measure] here’s inches, seven and three-sixteenths and let’s add another distance here. How about eighteen and and an eighth. Ok, so you got your sixteenths you got your eighths you gotta change the denominator leave the numerator add two divide by six carry the one thirty days have September, tipi canoe and Tyler too—and I can’t do it—alright without an abacus and three calculators.

Well, here’s the way to do it, metric—because look here, the tapes you can buy now, come with inches on one side if you gotta do it the old way and centimeters—metric on the other side. So all you have to is put it in like this and you get your nineteen centimeters added to forty six centimeters—that’s easy sixty-five. You can do the math. Metric is cool.

My reaction to this was much like the aftermath I experience following the viewing of an Ed Wood movie—vertigo. Beyond the fact that I don’t recall any big push “a few years ago” for metric, what are the odds that one would always hit integer values when using centimeters for woodworking? I suspect it would be approximately zero. The size of the measured board example appears contrived, and unrealistic. The “metric” example offered by “Mr. Shortcut” has the appearance of how an American, who has never actually used or experienced the metric system, imagines how the metric system might work. Mr. Shortcut (MS), like many U.S. “metric promoters” has not bothered to research the subject.

Mr Shortcut proudly shows that one can purchase a tape measure with both inches and centimeters (aka pseudo-inches). Independent of anything, dual scale instruments are evil. They simply allow the person using them to ignore the metric scale, use the familiar side, and continue to hinder metric adoption. This point is enshrined as Naughtin’s First Law.

When a person actually attempts to use centimeters in construction, they will quickly discover the need to use decimals. This often leads the average US citizen to believe that metric is not necessary and only the introduction of tape measures with decimal inches on them is. The use of decimal centimeters is awkward and leads to unnecessary numerical complication, which in turn leads to errors and scrap. This problem is well-known to the Australian and UK construction industries, and Bangladesh, Cameroon, India, Kenya, Mauritius, Pakistan, South Africa, New Zealand and Zimbabwe, but alas, in the US, we, and Mr Shortcut, are ignorant of their practices and our own U.S. metric construction code. The solution is, of course, to use only millimeters so the numbers measured are all whole numbers and eliminate the decimal point entirely. Decimals are great, they are the next best thing to whole numbers, but one should prefer expressions without decimals if possible. This is Naughtin’s Second Law: Prefer Measures Without Decimals.

Am I being a bit too hard on a person who is trying to promote the metric system? Possibly. His heart is in the right place, just not his tape measure. I spoke with my resident woodworking expert, Pierre, to get his view about the importance of measurement. He reminded me that a number of woodworkers completely eschew measurement of any type and build proportionally by eye. In Pierre’s words:

As we’ve discussed, plenty of woodworkers try not to use any measurement *at all* if they can help it. They know they can’t read a tape measure, that no two tape measures are identical, and they don’t want to do math, *ever*. But there’s probably a process here. First I convince them that math can be helpful, then *you* can show them that math can be easy.

I’m probably not qualified to convince any woodworker to use measures, so I’ll let Pierre work on that. But if they should happen to decide that measurement is useful, I can attempt to guide them away from centimeters and toward millimeters, which will make the math easy. That I do know.

Custom-cabinetry-design.com is a company with a name that describes what it does. They would very much like people to use millimeters and have a page which explains how easy it is. They state:

We know change can be difficult. But, we are confident that if you can count money, then the conversion to the metric system will not only save you time and frustration, it will eliminate costly and time consuming mistakes. Imagine no more fraction math, only dealing with whole numbers and half numbers is much easier than working in fractions.

The assumed unit of measure is the millimeter. They even offer a nice side by side example of how easy using millimeters is compared with inch-fraction descriptions:

It appears to me that there are those who have actually used metric to construct physical items, and those, such as Mr. Shortcut, who imagine what it might be like to use the metric system to build something. It is quite possible to build with centimeters, and carry along decimals. The path of least intellectual resistance for Americans is to use centimeters as a decimalized pseudo-inch. Or, one can use millimeters, measure with a ubiquitous centimeter rule, and constantly move a decimal point in one’s head as I did to obtain millimeters. I engaged in this unnecessary arithmetic complication until enlightened Australians guffawed at my ignorance and sent me millimeter only rulers and tape measures. This bad practice is encouraged because of the ubiquity of centimeter marked rulers and tape measures in the US and the minimal availability of metric only millimeter only scales here. The invisible metric embargo makes it very difficult to find a millimeter only tape measure in the U.S.. The only known product available is for carpenters, and called the True 32 tape measure. It has a length of 5 meters, and is marked in millimeters. Obtain one and use it. After you have, I suspect you would no more go back to decimal centimeters than you would contemplate using Roman numerals.

Don’t imagine the metric system—use it!

Related essay:

The finest gift I ever received from my late Australian friend and metricationist Mike Joy was an 8 m millimeter-only tape measure. It does mark the passage of meters, and hundreds of millimeters, but not centimeters. I still have it, and use it frequently, in my metricated apartment, and I can attest to the joy (pun intended) of measuring in integers. Mike was an avid supporter of millimeters as the FIRST usable submultiple of the meter. In my own practice of pharmacy, I can tell you that even the contemplation of centiliters is out of the question. All liquid volumes are wielded in milliliters. In 2011, the Institute for Safe Medication Practices took the historic step of joining this concept, recommending that only the milliliter be used for oral liquid medication measurement, and non-metric units banned from U.S. Healthcare.

You said “The path of least intellectual resistance for Americans is to use centimeters as a decimalized pseudo-inch. Or, one can use millimeters, measure with a ubiquitous centimeter rule, and constantly move a decimal point in one’s head as I did to obtain millimeters. I engaged in this unnecessary arithmetic complication until enlightened Australians guffawed at my ignorance and sent me millimeter only rulers and tape measures. This bad practice is encouraged because of the ubiquity of centimeter marked rulers and tape measures in the US and the minimal availability of metric only millimeter only scales here.”

I will argue you are doing it wrong, and show you a shortcut. Lets consider that 7-3/16 dimension that Mr. Shortcut converted incorrectly to 19 cm. I think we would both agree it is 182.6 mm, but lets round to 183 mm. On your True 32 tape, it is 3 mm hash marks right of the 180 mm mark, so you add 180 + 3 = 183. Now my tape is marked either in centimeters (your view) or millimeters with a suppressed zero (my view). It is 3 mm right of the “18” mark. I write down 18 and pad 3 to the right of it, 183 mm, done, no real difference. If it is right on a numbered mark you are padding a zero to the right of the number. It is completely trivial to use millimeters with a tape where the numbered marks are centimeters (as long as there are nine millimeter hash marks between, hopefully with #5 a medium line).

Suppressing the zero tends to allow for a bigger font and I don’t mind that. I also have the True 32 tape but I think its key advantage is other features supporting the 32 mm modular carpentry system for shelves, drawers, etc in cabinetry. If you accept centimeter numbering (but use millimeters as above) Starrett, Komelon, Milwaukee, and Lufton offer some metric-only tapes, but usually, you have to order online.

John S:

Although President Ford signed that metric conversion act into law, which could at the least be appreciated by those in this forum, something the President said later on unrelated to such still makes me chuckle, namely “medium household income”. Thus, I assume you meant ‘#5 a median line’.

Otherwise, thenks for another excellent posting!

No, I actually meant “medium.” Generally, the millimeter hash lines are short, the numbered lines, whether 10 mm or 1 cm apart, are long, and the 5 mm marks should not only be in the middle (median) but be of medium length. I have one ruler where all nine mm hash marks are equal length and I can assure you it is a bear to read correctly, I should just throw it out. The actual lengths of the lines are relatively immaterial and depend on the width of the tapes, but correctly using the properties of short, medium, long is critical. Imperial tapes use even more length steps to distinguish binary fractions.

Thanks, John, for the explanation; it’s clearer now. Wrt the QSI Corp ruler I use daily, it’s 250 mm long in increments of 10 mm, which would meet the Maven’s specifications. On closer look it is clear what you mean as the 5 mm, 15 mm, 25 mm, … hash marks are each a bit longer, and so can be descibed as “medium hash marks at the median of each 10-mm interval”.

Thanks for making this clear; such surely makes it easier to read correctly.

John S:

Although President Ford signed that metric conversion act into law, which could at the least be appreciated by those in this forum, something the President said later on unrelated to such still makes me chuckle, namely “medium household income”. Thus, I assume you meant ‘#5 a median line’.

Otherwise, thanks for another excellent posting!

The centimeter, better ÷10. Seems to be more of a pseudo barley corn than inch. The centimeter didn’t hinder my path to metrication, but the millimeter did win favor with me as I realized the advantages of using them. With that said, anyone promoting the metric system over the inch pound kludge should be encouraged and enlightened of the finer points. (eg. mm over cm)

Meter on!

Another point perhaps worth making here I saw a couple of days ago when a couple of surveyors used a long tape measure to measure various lengths of the house I live in. The units of such? Decimal inches! (Well, at least it’s an improvement over that hodgepodge of hash marks for inches that sickens us all…)

Maven and Others:

Here’s another reason why we should not drop those four nuisance prefixes entirely:

In the leading front-page article in today’s NYTimes on the massive landslide in Shenzhen, in the second paragraph, we find “…to search a 94-acre area…”

What in the world is 94 acres? My guess is it is a silly conversion from 38 hectares (38 ha), which is an easy-to-understand 38 square hectometers, which would be silly to state as 380 000 square meters.

Although “ha” is not part of SI formally, it is a good unit to have in the real world, and saying it is 10 000 m^2 if fine, but since 10 000 is a perfect square, a hectare is simply the area of a square with sides of length 100 meters, which Should be called a hectometer Because of the common word HECTare. (Just some FFT — Food For Thought.)