The Right Way, The Wrong Way and The American Way

Battlebots Trophy -- A nut with a 5 inch diameter hole with 4 threads per inch

The Battlebots Trophy — A nut with a 5 inch diameter hole and 4 threads per inch

By The Metric Maven

GAO Report Edition

Fasteners are ubiquitous. In physical design, they are everywhere. The image to the left is the current Battlebots Trophy, a giant nut. As of 2016, this nut celebrates US obsolescence with its archaic 5 inch diameter hole and four threads per inch.  The 1978 GAO report has an interesting chapter on fasteners, what happened, and what didn’t. The first sentence of the fastener chapter reads:

The U.S. fastener industry which was originally opposed to metrication, began conversion efforts in 1970 in order to maintain its markets.

The industry found that in the 1960s their major customers were moving toward the metric system. One would think the US fastener manufacturers would have been in favor of metric by 1978, but the story is more complicated than expected and perhaps too American. The Report has a nice description of a fastener:

A fastener is anything which holds two things together. Nuts, bolts, screws, rivets, cotter pins, and nails are a few examples. (See following page.) Of these, the United States produces approximately two million different types. Fasteners can hold together a vast number of items. For example, a telephone is held together with about 70 fasteners. Jumbo jets contain millions; and for one model, fasteners costs represent about 10 percent of the plane’s total cost. In short, much of the nearly $2 trillions U.S. economy is held together by the $2 billion fastener industry.

The report notes that a considerable increase in the use of metric fasteners is taking place in the US. The domestic fastener industry was also under pressure from imported Olde English fasteners. At the end of the 1960s, no US engineering standard for metric fasteners existed, but an international standard did. US industry representatives claimed that the international standard had too many sizes and thread types. The values of these sizes did not follow a logical pattern it was alleged.  If the US fastener industry was going to become metric, it was argued that the US should create a new fastener system that was:

….as perfect as possible. Also, the industry did not want to give a competitive advantage to foreign producers of metric fasteners. It was felt that the foreign producers would gain an advantage if the U.S. industry merely accepted the existing international  standard for metric fasteners in its entirety.

Yes, we in the US were going to produce a “more perfect fastener” or perhaps even a perfect fastener, and in January of 1971 the report “A Study To Develop An Optimum Metric Fastener System” was released by the Industrial Fasteners Institute. The study was presented to the ten largest corporations in the US as well as the National Bureau of Standards (NBS), and technical bodies in Canada. The selected group was unanimous in its view that a detailed study should be undertaken. The GAO Report states:

The Committee’s ultimate objective was to design a metric fastener system which would be so attractive technically and economically that it would become the single internationally accepted system of threaded fasteners. (7-5)

An unshakable US faith in technical Darwinism, coupled with the belief the US would create the fittest fastener meme propelled this new study. The Special Committee published its results in 1973. It recommended a fastener system with 25 sizes and a single thread type. The first metric fastener standard based on these recommendations was released in 1974. Before the standard was completed, the new system was encountering international resistance. Britain and German standards representatives released a paper called “Why Should the International Standards Organization System for Metric Fastener Threads be Changed?” It argued that the costs and confusion were unwarranted, “the technical advantages were minimal, and the system could hardly be called “optimum.” There were complaints of protectionism and everyone having to start all over again. (7-6).

The discussions continued from 1973 to 1977 as the ISO negotiated with its US members. The US representatives finally backed off from the proposed changes to the international standard. The US standard became essentially the same as the preferred series of the ISO standard.

There was controversy about the strength grade of fasteners in the 6 to 18 millimeter range. Europeans used an international strength grade of 8.8. It has a strength capacity of 116 000 pounds per square inch. The comparable US SAE was grade 5, which has a strength of 120 000 pounds per square inch. This is about a three percent difference. It was recommended the next higher grade 9.8 be used. This fastener has a strength of about 130 500 PSI.

The Europeans went along with the proposed change, but only the US automotive industry adopted the higher grade. US farm equipment, Canadian and European manufacturers decided to use 8.8 for their threaded fasteners. The unavailability of fasteners that met the US requirement caused concern that an 8.8 fastener could be interchanged for a 9.8 version during a repair. If 9.8 was not available, it would be necessary to use 10.9, which requires an alloy steel.


The report next focused on the head sizes for the fasteners:

A major problem arose during the attempt to reach agreement on the hexagon head size for three fasteners. This was probably the most hotly debated and difficult issue considered during the 1977 ISO meetings. The schedule below shows the head sizes wanted by the United States, those used in Europe, and those agreed to at the meetings.


The Optimum Metric Fastener System study had shown that the head size for a number of fasteners was unnecessarily large. International standard sizes were widely used in Europe, but the European representatives had in 1975 agreed to reduce the head size 1 millimeter on each of the three sizes. The U.S. representatives agreed to the compromise sizes in the earlier meetings, but in 1977 returned to the demand for a smaller head for the 10-millimeter fastener size.

The Europeans would not approve an inclusion of a 15 mm head and the US would not compromise. The official standard became 10, 12 and 14 millimeter diameter fasteners with 16, 18 and 21 millimeter heads respectively. The US would use these and the 15 mm head. It became possible that several head sizes might be used for these three fastener sizes. The Report noted:

Head sizes (like strength grades) are an example of an international standard which is formally agreed to on paper but not uniformly adhered to in practice. (7-8)

The European view was that the benefits of the changes to the new system did not justify the expenses involved. The fastener standard is voluntary, and the US could do whatever it wanted. This impasse could leave US fastener manufacturers holding the bag. The GAO report states:

An official of one company told me he had stuck his neck out and stocked six metric sizes in 24 lengths. The stock included the 6.3-millimeter fastener which was one of the U.S.-proposed sizes that did not gain international acceptance. This size was being used by a major automobile manufacturer in its 1977 and 1978 models. However, the automobile manufacturer has dropped it for future models.

It was noted that maintaining Ye Olde English and metric fasteners in the US could cause considerable difficulty:

It is virtually impossible to visually identify some sizes of customary-threaded fasteners from similar-size metric fasteners. It is possible to mismatch 36 combinations of customary- and metric-threaded fasteners. The result could be either stripping during assembly or full assembly with 25- to 60-percent loss in load capacity. Thus, the accidental mismatch of fasteners could result in fastener failures.

This is a very good argument for a quick metric switch-over, with an M-day, and no “transition period,” rather than waiting for the magic of the Metric Philosophers technical Darwinism to accomplish this task over an undefined period.

On April 25, 2014 (2014-04-25), Joe Greenslade of the Industrial Fasteners Institute gave a presentation titled “Metric Fastener Standards Transition”  His view is that one metric fastener system should be used throughout the world. Mr. Greenslade calls the US attempt to create an “Optimum Metric Fastener System” a “misguided move!” He claims that from 1975 to 2013 there has been a slow but gradually accelerating adoption of metric designs.

Greenslade identifies three different fastener systems, ISO (International), DIN (German) and ANSI/ASME/ASME/SAE (US). He sees the US Optimum Metric Fastener System (OMFS) as a misguided philosophy of “since we must change we will do it better than you Europeans do.”  The OMFS attempted to eliminate fine threads, this “simplification” was rejected. The US introduction the M6.3 X 1 fastener simply because we wanted a metric version of a 1/4-20 Ye Olde English fastener, rather than using a standard M6 x 1.0 was rejected. The introduction of a new thread gauge was not accepted. The US wanted to replace the hex head with a new spline head, but that was also rebuffed. The changing of hex sizes (head sizes) by 1 millimeter on M10, M12, M14, and M22 is still causing confusion to this day. The US has finally withdrawn its proposed “optimum” metric standard.

The two metric standards that remain are ISO and DIN. DIN is very, very close to the ISO standard. They are 99.99% interchangeable, and 90% identical. The German DIN standard is to be replaced with the ISO standard. When US customers now ask for ISO they are often told “we do not stock any ISO — only DIN.” Greenslade indicates that a search for dual DIN/ISO designations on existing drawings and parts lists should be undertaken, and in these instances they should be edited so that only the ISO number is used. He also suggests that all new product design drawing designations be only ISO. Greenslade offers numerous examples of this existing redundancy “out in the wild.” The long term objective for the USA should be to use ISO and forget the past.


baskin-robbinsThe US introduction of an “optimum” standard in the 1970s has the fingerprints of American hubris all over it. Rather than finally bring some order to the chaos that is side by side Ye Olde English fasteners and metric, by eliminating the “custom”-ary versions, and using ISO metric exclusively, we instead opted to show everyone “how to do it better.” History has not judged us favorably, and the exercise in imposing a US metric “standard” on the world continues to cause discord and confusion to this day. As has been said many times “the great thing about US standards is there are so many to choose from.”

Related essays:

Without Metric Threads We’re Screwed

A Hole in The Screw Head

The Metric Maven has published a book titled The Dimensions of The Cosmos. It examines the basic quantities of the world from yocto to Yotta with a mixture of scientific anecdotes and may be purchased here.


The October Report Three Decades On

october-countryGAO Report Edition

By The Metric Maven

The Beginning and The end

In October of 1978 The General Accounting Office (GAO) of the US issued a report titled “Getting A Better Understanding of The Metric System–Implications If Adopted By The United States.” It is a snapshot of the late 1970s solipsistic view of US metrication as the rest of the world converted to the metric system. The report seems very uneven in its views and understanding of the metric system. It has the look of a report by committee where those who wrote each chapter might have been insulated from one another.

The report is clear on asserting that a decision has not been made to convert to the metric system by the United States of 1978. My reading of the 1975 Metric Hearings are in line with that statement. “…the national policy is not to prefer one system over the other but to provide for either to be predominant on the basis of the voluntary actions of those affected.” It is also stated by the GAO that:

“The [metric] Board is not to advocate metrication, but is to assist various sectors when, and if, they choose to convert.” It is also “…to encourage retention of equivalent customary units (usually by way of dual dimensions) in international standards or recommendations;” (1-10)

The methodology used by the GAO was essentially to undertake extensive polling of multiple US industries, and finally the public, about how they thought metrication would affect them. The polls could only measure emotions as their targets of the inquiry. The US had not experienced any metric change and therefore the participants could only provide a visceral viewpoint. Not surprisingly, small businesses believed the disadvantages would outweigh any benefits.

The GAO begins with responses that are congruent with long-time US economic mythology:

Present sizes have developed over the years in the marketplace to meet demand.  … There is little doubt that increased standardization and rationalization could result in benefits, although this objective could be achieved using the customary system.

This is the sort of false equivalence that can be asserted when no specifics are studied. One can imagine a person who currently uses Roman Numerals, and has never encountered Hindu-Arabic ones, might make the same statement.

The beginning of the report seems like a strange loop of inconsistency (pg vii):

The total cost of metrication in indeterminable in spite of various estimates that have been cited in the last decade by various organizations  and individuals.

and two paragraphs later:

However, based on the limited cost data that was available to the GAO and the input from various representatives from a wide spectrum of organizations throughout the country, the cost will be significant–in the billions of dollars.

In a swelling of ersatz democratic pride the report indicates:

Since a decision will affect every American for decades to come, GAO believes the decision, which is to continue with the current policy or change it, should be made by the representatives of the people–the Congress.

The beginning of the report continues its emphasis on what the current policy is and launches into a short history of the metric system. The Adams Report of the 19th century is quickly encountered. The GAO points out:

Adams concluded in his report that the Congress should not change the existing system but should fix the standards for the units. …. He believed that the time had not yet arrived in which he could recommend

* * * so great and hazardous an experiment * * *, as that of discarding all our established weights and measures, to adopt those of France in their stead.

A discussion of Adams’ Report on Weights and Measures may be found here.

The GAO quickly mentions that the Mendenhall Order was “an administrative action.” In light of their democratic stance, that only Congress should make changes, one might question their view of the validity of the Mendenhall Order. The technical superiority of the contemporary 19th century metric standards and the failure of the British ones was not mentioned as the driving force for this ad hoc legal patch by Thomas Corwin Mendenhall (1841-1924) which Congress ignored.

The 1971 National Bureau of Standards Report  A METRIC AMERICA, A Decision Whose Time Has Come is mentioned with this interjection:

A major area of controversy was the impartiality and completeness of the NBS metric study. The critics, which included former members of the study group and its advisory panel, contended that NBS was biased in favor of conversion while performing the study and reporting the results.

Then an interesting historical tidbit is related:

Metric conversion legislation was passed in the Senate in 1972 providing for a predominantly metric America within a 10-year period. It was introduced into the House where no action was taken.

This may be the closest the US has come, from a legislative standpoint, to becoming a metric nation.

The GAO report generally interprets the metric system through Olde English measurement usage, and not as a new and upgraded way of implementing measures. The report states “Millimeters and centimeters would be used instead of inches and feet.” (2-2) They then offer an inch/centimeter ruler as an example. Think about the statement and it should be clear that millimeters are not like inches or feet, not even with a shoe horned barleycorn. The reader is told that “The metric system is decimal because prefixes are used to indicate multiples and sub-multiples of 10. The majority of metric prefixes use 1000 and this is clearly the best practice for implementing metric quantities. Yes, this practice was known and encouraged in 1978, see the essay: Who Says!?. The GAO has an objection to the pascal that is frivolous: “The major objection to the pascal is that it is too small of a unit with which to work. It takes about 1,000 pascals to equal 1 pound per square inch.”  So a Kilopascal would be about 1 pound per square inch?—and this is a problem how? Just use Kilopascals. That’s a unit.

A more legitimate complaint is that a pascal is rather abstract (a view that I share). This can be remedied easily by using newtons per square meter instead of pascals.

Chapter 3 of the Report highlights ascribed advantages and disadvantages of metric. The initial positive aspects related by the GAO have been covered by Pat Naughtin many times: 1) Conversion would provide opportunities for worthwhile changes [needed industrial reforms to implement efficiency] and 2) Conversion would stimulate the economy. There is no discussion of the advantage of using millimeters versus centimeters, no discussion of whole number usage with milliliters, and grams and how that could simplify matters, just vague platitudes.

The ascribed disadvantages of the metric system begin with an appeal to the mythology of technical Darwinism, and an appeal to the “practical” over the theoretical:

The Customary System is a better measurement system

The U.S. customary system is tailored to meet practical everyday needs of human beings. It is firmly established, and is not obsolete or complex. It came into being by natural selection. Although use of the metric system has been legal in the United States since 1866, the customary system survives because it meets a need. …. “

The same old Goldilocks pseudo-arguments about Ye Olde English measures are paraded about:

The meter, about 4 inches longer than the yard, is too great a length for general application, and the gram is too small to be practical. Metric names are more difficult to say and remember.”

Without a pottle of porrige in an 18 barlycorn wide bowl for Goldilocks, how could she fathom what 250 mL might be?

The Report has no clear conclusions on US trade, as that is the answer which came back from the questionnaires sent to representatives of the Fortune 500. The GAO surveyed people in Business, and discovered that:

“Few of the respondents knew the U.S. policy on metric conversion. As the following chart shows, almost half of the respondents believed conversion to be mandatory.” (5-13). and “Few believed the Government should legislate or enforce conversion.” (5-21).

There are many other chapters in the 1978 GAO Report, but the information they contain would be best examined in separate essays. Here we will look at the overall view of the GAO toward metric conversion. We will now skip to the end of the Report and look at the GAO conclusions for an answer. Chapter 30 of the Report examines lessons learned by foreign countries. If the US decided to become metric, here is the GAO’s list of what we should embrace:

— A firm Government commitment to convert is necessary.

— A central body should be established early to plan and coordinate the conversion and inform the various sectors of the economy and the public of metric activity.

— A well-developed plan and effective coordination by industry and all sectors of the economy must be accomplished.

— A voluntary conversion must eventually become mandatory through laws and regulations, etc., in order to complete the metrication program.

— Overall and specific target dates must be used.

— The public must be adequately informed and educated, and responses must be made to consumer concerns because conversion of the retail sector is most difficult.

— Letting costs lie where they fall can be adopted in whole or in part.

— Government purchasing power can be used to propel the conversion.

— The conversion of certain sectors, such as in sports and weather forecast, can aid in metric education.

— Periods of dual marking should be kept to a minimum

— Hard conversion of products is more desirable than soft conversion whenever practicable to obtain benefits.

I was quite surprised. The list makes for a set of very good guidelines for the most part. I would not allow dual marking at all. Whoever wrote this section has a good understanding of the problems involved. What I was not prepared for was a very self-introspective view:

Another difference between these countries and the United States is the type of governments. Basically, the foreign countries have a parliamentary type of government in which the executive is also the leader of the legislative branch. Two of the foreign countries only had to change national laws to effect metrication. Australia, with six State governments, and Canada, with ten Provinces, had to change some local laws. The changes appeared to be well coordinated. The United states has a Federal Government and 50 State governments. Metrication would necessitate revisions in the laws of each of these government entities. Because of the differences in government, the other countries’ decision making process, including changes to laws, regulations, ordinances, and codes, is less complex than the United States.” (30-4)

The Report points out the frozen nature of our Republic:

Other countries established their metric organizations early in the conversion process. One month after Australia enacted its metric legislation, the metric board had its first meeting. In New Zealand the metric board had its first meeting 10 months after the decision to convert had been made.

The Metric Conversion Act of 1975 provides for a U.S. Metric Board to coordinate the voluntary use of the metric system. …. However, the Metric Board had not become fully operational at the time this report went to print, more than 2 years after passage of the act.” (30-7)

In Chapter 31 the GAO exposes the misuse of the word voluntary in 1975:

In other countries that are converting, “voluntary” means that the various sectors voluntarily agree on how and when to convert within the over-all parameters of a national commitment to convert to the predominant or sole use of the metric system during a specific period of time, usually within 10 years or less.  In other countries voluntary was not a choice of whether to convert or not, as in the United States.

In the 1975 metric hearings, this confusion about the word “voluntary” was used to disingenuously equate the legislation passed by the US Congress with that of Australia and other countries.

The GAO Report then provides a side-by-side summary of the differences between the US approach and other countries. Here I reproduce them in full:


The idea that “we tried to go metric” in the 1970s is simply ludicrous. What is most interesting is the fact that the GAO Report, which starts out as a very anti-metric document, ends by explaining what should be done for the US to become metric. It also lays out the hurdles involved with the legislative molasses known as our government that keep any meaningful reform from occurring.

The GAO report is a 767 page tome of a document. It contains many interesting metric stories which I plan to focus on in future essays. This essay demonstrates that the anti-metric GAO Report is much more complex (and muddled) document than it is generally thought to be. It has some information that is quite relevant to our current zero-kelvin metric situation.


The Metric Maven has published a new book titled The Dimensions of The Cosmos. It examines the basic quantities of the world from yocto to Yotta with a mixture of scientific anecdotes and may be purchased here.