The Metric Hogshead, A Unit Whose Time Has Come

Posted on 2012-04-20 by Randy Bancroft

By The Metric Maven

Bulldog Edition

Arnold – The Metric Hogshead Inspiration

When I was a very young boy, I often watched the Gerry Anderson program Fireball XL5. Space exploration was paramount in peoples minds at the time. In the program, the puppet crew of the spaceship, became space happy with the space prefix. According to my friend Sven, they had a space circus, space generals and it was insinuated that a space ice cream truck existed. The magic prefix “space” could transform any ordinary mundane object or concept into a modern one that was now space ready.

This type of magical prefix incantation practice somehow became a tool for US metric aversion. If the metric system is the wave of the future, there’s nothing wrong with our old units that affixing a prefix can’t fix. Sometime in the past, it was decided by metricphobes, that they could create metric imperial units out of the vacuum of space, by merely using the word metric as a prefix. Poof! suddenly we have a metric ton, a metric grain and a metric carat.

Metric ton, now there is a unit worth banishing, yet it is also officially called a tonne, so you will know it’s a metric ton and not a long or short ton. Some creative person even decided to double down on the absurdity, and sometimes I see it written as metric tonne. A tonne by any other name would measure as bad.

The original word ton is of obscure origin and seems to be related to the weight of a wine cask, called a tun. How much mass does a metric ton have? 1000 Kilograms, or more properly, 1 Megagram. So why don’t we just call it a Megagram, instead of a metric ton? I have no idea. The confusion between metric tons (1000 Kilograms), long tons (1016 Kilograms) and short tons (907 Kilograms) has caused a number of trade misunderstandings—to this day. The recommended symbol is t for tonne. With mt or MT meaning metric ton. Of course we could just use metric directly, and call it a Megagram with the respresentation Mg. Well, we can’t use this symbol, because people could possibly confuse it for a milligram—that’s what I’m told.

Obviously mg and Mg could be confused, but would it really be a problem in practice?
Am I to believe that no one, other than a fisherman, would be able to figure out that a boat which has caught 34 mg of fish would not make sense. Or be so credulous, if I purchased
a bottle of vitamins, that I could easily confuse 200 mg tablets for 200 megagrams? The two units are 1000000 times different. I’m also to accept that two representations of metric ton, mt and MT solves the Mg problem?

The difference between a milligram and microgram is of concern to pharmacists. This could be a serious error. I note that for milligrams the representation used is mg, but for micrograms, it’s MCG. Perhaps we could have MAg?–for Megagram—or some other three letter acronym, and ditch the metric ton, which is neither metric, nor a ton.
A metric grain is a unit we can clearly do without. Imagine how confused Americans would become if we did not offer them 5 grain aspirin, and they were offered only a 325 mg label on the package. I believe the answer is not at all. Ask anyone on the street how big a 5 grain aspirin is. What do you think the odds are they would know?

A metric carat is 200 milligrams. The word carat is a word for carob seed. Yes, we apparently need a metric value for a carob seed in order to make mass measurements of gemstones. We can’t use metric grains, they’re wheat!–and are 1/4 of a metric carat. They are obviously not suited for gemstone measurement—only carob seeds are.
The metric carat is then subdivided into 100 points of 2 mg each. The reason we could not just use milligrams would be???? I don’t know, but could it be, that if we were in space we would use space carats instead? Or perhaps there is great concern by jewelers that we would confuse a 20 mg diamond with a 20 megagram one? We must certainly guard against this danger. With a density of 3.5 milligrams/cubic millimeter, a 20 mg diamond would have a volume of 5.71 cubic millimeters. A 20 Mg diamond, would have a volume of 5.71 cubic meters!

What is the reported weight of the Hope Diamond? It’s 45.52 carats! Where are the points! The units are carats and points–right? I hate to go against the respected “tradition” of diamond merchants, but 9.1 grams seems like a more understandable value. That is about nine plain chocolate m&m’s. Now don’t confuse them for mm.

The Smithsonian describes the Hope Diamond as weighing 45.52 carats, with dimensions of Length: 25.60 mm, Width: 21.78 mm, Depth: 12.00 mm. Would it confuse people more if it were 9.1 grams with those length dimensions, all in metric?

There are eight different lattice structures of carbon, why does carbon in a diamond lattice deserve its own pair of metric-non-metric measurement units? One certainly can’t argue that it’s somehow color—diamond dust is black. I once saw the diamond dust Andy Warhol used in his work Andy Warhol’s Diamond Dust Shoes at The Des Moines Art Center, it’s black, and hypnotically shimmers.

The use of carat appears to demonstrate a significant advance in marketing, but a retreat for the science of measurement. The carat, metric or otherwise, should be cast into the nether-regions and never allowed to return. Grams are satisfactory thank you.

When I was in college, an important measurement mystery confronted me: how much beer is in a keg? I seemed to get multiple answers. Finally I was told by a beer distributor that there is no standard beer keg size. This is still true to this day. This is from Wikipedia:

“Since keg sizes are not standardized, the keg cannot be used as a standard unit of measure for liquid volumes. This size standard varies from country to country and brewery to brewery with many countries using the metric system rather than U.S. gallons.“

It’s clear to me that something must be done about this egregious trespass by brewing companies. How can we continue to allow them to prey on innocent drunken college students! I therefore propose the Metric Hogshead, defined to be 200 liters. A metric keg would then be defined as 50 liters or 1/4 of a metric hogshead. Finally standardization has been imposed on a runaway system of measuring beer. You’re welcome America!

What I’m lampooning here, is what the world had prior to the metric system: endless, unnecessary, different, and inconsistent measurement units. Imagine if gasoline, milk, water and paint all had their own volume units, that changed from town to town and country to country around the world. The chances of making a mistake or being deliberately cheated by inconsistent and arbitrary weight and measurement definitions would be ubiquitous. That is what we had before 95% of the world’s population agreed upon one uniform system of measurement for volume–the liter. It is only in the US that we would rather makeup imaginary versions of metric measurements, and create metric kegs and metric hogsheads rather than legislate the metric system. School’s Out, let’s forget metric hogsheads, metric tons, metric grains, metric carats and just use the metric system.

If you liked this essay and wish to support the work of The Metric Maven, please visit his Patreon Page and contribute. Also purchase his books about the metric system:

The first book is titled: Our Crumbling Invisible Infrastructure. It is a succinct set of essays that explain why the absence of the metric system in the US is detrimental to our personal heath and our economy. These essays are separately available for free on my website, but the book has them all in one place in print. The book may be purchased from Amazon here.

The second book is titled The Dimensions of the Cosmos. It takes the metric prefixes from yotta to Yocto and uses each metric prefix to describe a metric world. The book has a considerable number of color images to compliment the prose. It has been receiving good reviews. I think would be a great reference for US science teachers. It has a considerable number of scientific factoids and anecdotes that I believe would be of considerable educational use. It is available from Amazon here.

The third book is not of direct importance to metric education. It is called Death By A Thousand Cuts, A Secret History of the Metric System in The United States. This monograph explains how we have been unable to legally deal with weights and measures in the United States from George Washington, to our current day. This book is also available on Amazon here.

Without Metric Threads We’re Screwed

Posted on 2012-04-10 by Randy Bancroft

By The Metric Maven

I only had a casual acquaintance with screws during much of my working career. Where I worked there were clear plastic organizers with machine screws inside, and label designations outside like #4-40, #6-32 and #1/4-20. I had little idea what the nomenclature meant. One day I decided it was time for me to cure my ignorance. I discovered rectifying this lack of knowledge would be much more of a herculean effort than I expected.

I asked a number of people what the designation #4-40 meant, as I had seen a large number of these machine screws used on projects. The answer was almost uniform, and went something like this: “The 40 means forty threads per inch” I would then ask what the #4 designated. This was generally met with a blank stare and speculative guessing would commence.

Finally I met an engineer who knew the answer off the top of his head. He told me that below 1/4 of an inch the number was in gauge, above that the designation was in fractions of an inch. I was gobsmacked, and could not make any logical sense of this. When I looked up a dictionary definition of gauge, I discovered that it had the alternative spelling of gage. The definition that seems to fit this situation is: “A standard dimension, quantity, or capacity.” What was the dimension of the gauge size below 1/4 inch? After some research I found this answer:

“In Unified threads (measured in inches) there are numbered diameters #0 through #10, with 0 the smallest and 10 the largest. (Diameters #12 and #14 may also be found, but are usually on older equipment and needed for repairs or restorations. #14 is close to, but not exactly the same as, 1/4-inch.) The major diameter in Unified threads = 0.060″ + 0.013″ x (numbered diameter). So #2 has a major diameter of 0.086″. The odd numbers exist, but the even numbers are in far more common use.”

WHEW!!! This is how we designate screws in the US?! So you take 60 thousandths of an inch and add the gauge number times 13 thousandths of an inch to obtain the size in inches from the gauge number!!!? This is what we viscerally protect as a rational method of articulating screws in the US? But the given diameter formula only is valid for the gauge numbered screws. Above 1/4 inch, the values are directly in inches—well as directly as a fraction may be called “direct.” One generally has to compute a decimal value from the fraction to actually perform computations. It is clear that even this demarcation at 1/4 inch is an apparent ad hoc attempt to merge the two separate nomenclatures, given that #14 is close to 1/4″.

We see that #14 would be 0.242 inches and #1/4 is 0.250 inches. One can see that this is only a 0.008″ or 0.2 mm (200 um) difference between screw diameters. It is not difficult to imagine many situations where this size similarity caused mistakes. The answer offered to solve this problem appears to be “just stop using #14.”

Recently I met a former machinist who smiled when I told him “I only use metric in my designs.” His countenance indicated he really didn’t see that changing to metric was anything other than a frivolous, fringe issue. I looked at him and asked a simple question: “what size drill bit do you choose to allow a #4-40 screw to just pass through a sheet of material?–to produce a friction fit.” Suddenly his face became blank with uncertainty. “What I usually do is get a pair of calipers and measure the diameter in inches and then choose a drill bit.” I then asked what type of drill bit designation he then used to obtain the correct drill bit size based on his measurement.

There is more than one option. A fractional set of drill bits does not match the decimal inch value he measured with a calipers. He would need to first go to a decimal equivalent chart and choose the closest fractional drill bit size. A #4 screw has a diameter of 0.112″ according the the formula. The closest fractional size is 0.125″ which is a 1/8 inch drill bit. That’s as close as it gets! There are also US number and letter size drill bits, but I’ve tortured myself long enough explaining this Rube-Goldberg method of just trying to figure out what size drill bit to choose, for a given screw, when using imperial measurement. I didn’t inquire, but I suppose the former machinist is content to measure all the candidate drill bits with his calipers until he finds one acceptable. How is it we are content to have size designations on screws and drill bits that have no correlation?—and reject any change or reform?

Let’s now explain how screw threads are designated in metric. The closest size screw in metric to a #4-40 machine screw is M3. What does M3 mean? Well, the M means metric and the 3 means three millimeters in diameter. My metric drill index has a three millimeter diameter drill bit, which if I then drill a three millimeter hole, allows the three millimeter M3 screw to just pass through the plastic, metal or whatever sheet material I drill. Yes I have done this, it works. It’s that simple! If you want some clearance choose a 3.1 mm drill bit or 3.2 mm. They’re both standard sizes.

When Australia switched to the metric system in the late 1970s, their manufacturers quickly discovered they could get rid of a large amount of screws and bolts they stocked. One car manufacturer was able to reduce their inventory of fasteners by 80% which saved considerable money. The small business community in this country, who use commonly available imperial fasteners, don’t realize that without metric threads they’re screwed.

Related essays:

Don’t Get Engaged With Gage

A Hole in The Screw Head

Yes! We have no metric drill bits.

If you liked this essay and wish to support the work of The Metric Maven, please visit his Patreon Page and contribute. Also purchase his books about the metric system: