Don’t Get Engaged with Gauge

By The Metric Maven

Bulldog Edition

One day many years ago I had a strange experience with a word. It lost its meaning. I could pronounce it, and think about it, but the word had become temporarily disconnected from its assigned meaning. The sensation was one of disengagement with a description of  my world. Thankfully I experienced this for only a short period of time. Recently I discovered this phenomenon  has a name: semantic satiation. Here is a definition:

Semantic satiation (also semantic saturation) is a psychological phenomenon in which repetition causes a word or phrase to temporarily lose meaning for the listener, who can only process the speech as repeated meaningless sounds.

Semantic satiation describes a situation where a word has a meaning but it is temporarily lost. I have also experienced the loss in meaning of a word that is not just used in a repetitious manner, but is also assigned a multitude of meaningless meanings. This word also has at least 14 definitions. This mercurial word is gauge.

We have 12 gauge shot guns, wire gauge, railroad gauge, drill bit gauge, stubs iron wire gauge, sheet metal gauge, film gauge, loading gauge, structure gauge, and who knows how many dimension gauges of which I’ve never heard.

But gauge can also refer to a measuring or comparison device such as an air gauge, rain gauge, gauge blocks, water gauge, needle gauge, and many more.

The idea of gauge is batted about by Engineers and technical people with certainty—as if there should be an immediate comprehension. Yet, if you examine gauge as a dimension standard, you will immediately realize this is an oxymoron. Gauge is a dimensionless number. Gauge seems to be the measurement equivalent of the throw away phrase “Ya know what I’m sayin’?”

For instance, let’s suppose I want to drill some holes into a printed circuit board for a solid bare wire to pass through. I want the wire to have a hole that is as close to its diameter as possible. If I had a metric wire with a diameter of 1 mm, I could go to my drill index and select a 1 mm drill bit. It would then be easy to drill a hole as close as possible to fit the 1mm wire. Metric wire sizes correlate with metric drill bit sizes. It’s so easy even a caveman could do it.

There is only one problem with this simple solution, I live in the United States and thus far I’ve found no distributor of metric wire. I must rely on American Wire Gauge for wire sizing. I must go to a wire gauge table and find the American Wire Gauge number is 18 (AWG 18), for wire which has a 0.0403″ diameter (1.024 mm). The wire gauge numbers go from 0000 (0.4600″) to 40 (0.00314″) with larger gauge numbers proportional to smaller sizes.

Now I need to find a drill bit with a 0.0403″ diameter. The gauge sizes for drill bits are from 1 to 80 and A to Z. I locate Drill bit gauge 59 which is 0.041″ (1.041 mm). This is close to 1 mm and probably acceptable, but the wire gauge number is 18 and the drill bit gauge number is 59. There is no correlation. Don’t ask 18 what?, or 59 what?, they are just dimensionless integers, chosen by our infallible Anglo-Saxon ancestors–who used three barleycorn in a row to define an inch—and used the weight of 7000 barleycorns for a pound.

Why does the drill bit gauge designations change from numbers to letters?—I have no idea. This complete lack of correlation between gauge sizes of wire, and drill bits, illustrates that gauge is a meaningless dimension designator. Gauge simply stands between you and a useful, accepted, accurate, and understood dimension—like millimeters.

I find myself astonished that there is considerable resistance to metric system adoption, even when I point this irrationality in gauge designation out to machinists. It begins to look like they want a set of mystic runes to read, so their profession remains esoteric, and difficult to understand by outsiders. Why have a system this confusing?—when there is one—the metric system—which is ready to go. If you have 0.7 mm wire and a drill set with a 0.7 mm bit, what’s to dislike? No look-up tables, no strangely odd numbers and letters, just drill the hole.

How about American Standard Sheet Metal Gauge?  Let’s take 19 gauge sheet metal, how close to a millimeter thick is that?  Well it depends on the material:

Gauge       Steel               Stainless Steel           Aluminum                  Zinc

19     0.0418″ (1.06 mm)     0.044″ (1.1 mm)     0.036″ (0.91 mm)     0.060″ (1.5 mm)

So what does gauge number mean if the dimensions are all significantly different! It doesn’t seem to represent a constant dimension.  Why on earth can’t we just shoot for say 1 mm +/- a tolerance?—and have numbers with units attached? Or, if there is a manufacturing reason for the differences, just use millimeters. The larger the gauge numbers for sheet metal, the smaller the thickness. If we want the closest 1 mm drill bit, it’s 59 gauge. The closest 1 mm wire is 18 gauge.  The closest 1 mm sheet of metal is 19 gauge. We won’t even go into Stubs Iron Wire Gauge, and tubing gauge. There is no rational correlation between gauge number and physical dimensions.

A 12 gauge shotgun has a barrel diameter in which twelve balls of lead, of the same diameter as the barrel, are equal to one pound. It takes twenty lead balls of the same diameter as the 20 gauge shotgun barrel to equal a pound. What if you obtain a .410 shotgun?–well that’s in caliber.  I would argue that 9 mm is more descriptive than 12 gauge, 20 gauge or .410, even to Americans.

The use of gauge, as a  size description in America,  is a perfect illustration of the completely irrational dimensional arrangement of our building construction materials. They are the materials that drive our physical economy.  This causes confusion and waste, for no reason. Our system is long past being ripe for reform—it’s rotting. I don’t understand why the American public, and the technical community, doesn’t demand mandatory conversion to the metric system. I just can’t gauge why.

Related essay:

Without Metric Threads We’re Screwed

3 thoughts on “Don’t Get Engaged with Gauge

  1. In the future, I’m going to have to be more careful, following your links. I finally got curious enough about the Stubs Iron Wire Gauge to click it. I learned that the Stubs Iron Wire Gauge is (1) “nearly obsolete” (no surprise there), and (2) it is nevertheless still used to specify “the outside diameter of hypodermic needles, catheters, and suture wires.”

    …nearly obsolete…hypodermics, catheters, sutures…I did not need to know this.

    But there is a further link to something called the “French catheter scale.” It is not possible to not click on something like that.

    It seems that a 19th-century maker of medical equipment, in a metric country, decided he just couldn’t live without a special scale for…catheters. This is disturbing enough, but the scale he came up with was in thirds of millimeters. To get the diameter of a catheter in millimeters, you divide its “French gauge” by three. So now we have a conversion factor of 1 ⁄ 3 shoehorned into a metric context. I really did not need to know this.

    The scale is also called Charrière, after the perpetrator. I think I prefer that: calling it French may be an unfair generalization. Although they did put him in the Legion of Honour.

  2. Well I guess you can use gauge as a comparison to anything and actually have it mean nothing compared to anything else.

  3. Don’t forget the paris point system for shoes. It seems to be a French thing to invent a great system, but then ending up not making it too good. Oh, let’s have prefixes for the units, but not for megagram, we’ll call it tonne instead, if that doesn’t rub people the wrong way I don’t know what will.

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