Making Fun of DIN to ISO Conversions

Things have changed and I intend to embody that truth within this article. As an ex-high school science teacher, I’ve learned that there is no better way to truly engage an audience on a topic that is innately bland and technical than to incorporate the points that need to be driven home within a story. Here is the story of my first year in the industry. You will find that I incorporate bits of technical information for your consideration so that you can apply that knowledge as you make careful decisions about other conversions. Furthermore, I will name drop some people and resources that could be helpful for you as related to this subject particularly and very likely in relation to other subjects as well.

If there is one thing 2020 has taught us it must be that change is inevitable, but sometimes it can be for the good and usually it is awkward. I’ve been fortunate to work as the social chair for Young Fastener Professionals during this time. This opportunity has allowed me to talk consistently with business leaders across the country. Within the array of opinions about COVID-19, I have noticed a common theme: the industry is changing and quickly. Some changes are good, like leaders learning the necessity of compassionate leadership or the  implementation of technologies to better enable our various systems. Some of that change is a bit awkward as we convert to new ways of doing things, including innovative ways to engage customers, while accounting for the relatively “old-school” approach our industry tends to favor.

The same is true for the story of DIN to ISO conversions. Eurolink Fastener Supply Service specializes in sourcing and importing hard to find metric fasteners, particularly those that are to a DIN or ISO standard, and we just celebrated our 20th anniversary in July. In the twenty plus years that we’ve been in business, we have watched and participated as the industry has moved to embrace ISO standardized fasteners. I am very fortunate to be with a company that highly values precise technical knowledge and has staffed a team of highly experienced and knowledgeable employees whom have been willing to mentor me without hesitation.

After a few months into joining the industry, I was invited by Brian and Eric at Fully Threaded Radio to discuss DIN to ISO conversions. They had seen my weekly VLOGs in which I would break down the differences between the DIN and ISO standards for similar fasteners and wanted my input on some questions related to these standards on their “Screwzapalooza” episode. We started off with some light conversation of course, like how the common metric standard for full thread hex head cap screws, DIN 933, overlaps with ISO 4017, with some exceptions, namely at the M10, M12, M14 and M22 sizes, and how these differences are consistent with their DIN 931/ISO 4014 counterparts (partial thread hex head cap screws). That’s when Brian put me on the spot and asked, “Why ISO standards though?”, followed by an unabated roasting of the French. I suggest giving that segment a listen, just for a few laughs at Brian’s wit and my nervous laughter.

In short, the answer I gave Brian was non-pedantic, possibly a bit reductionist, but true. For essentially the same reasons fastener standards in general are so important, as discussed in the article by Laurence Claus in Distributor’s Link Volume 43. N0. 2, an international standardization for fasteners has become relevant and will obviously only become more pertinent.

DIN stands for Deutsches Institut für Normung (German Institute for Standardization). As their name implies, they are a German  standardization organization that has come to be internationally recognized and essentially the go-to standard for the metric fastener industry in the United States and many other countries. Before and during that climb to high market saturation, standardizing bodies for other nations, including the U.S., created similar standardizing literature to meet the needs of their own nations.

While the International Organization for Standardization (ISO) has technically existed since the 1920’s, as the world has become more  globalized, communications faster, and logistics more efficient, supply chains that once existed almost within the boundaries of nations are now reliant on global trade. Due to the prevalence of global supply chains, it is reasonable to consider that a fastener in Italy needs to meet the same dimensional standards for an application that is distributed in Brazil, Canada, or Taiwan. Considering the infrastructures in place for
the production and distribution of fasteners at the local, regional, national, and international levels, it makes sense that stocking distributors in each of these countries would need to stock fasteners for OEMs or MROs using these parts. It also makes sense that OEMs would engineer products to require such parts as they would be available and internationally recognized, agreed upon and therefore consistent and theoretically stocked nearby.

These sensible posits are theoretical because we “fastenerds” are a hard-headed bunch here in the United States. In that “Screwzapalooza” episode of Fully Threaded Radio, Eric starts off by commenting on how he enjoyed that I started off my VLOG episode on DIN
933/DIN 931 to ISO 4017/4014 conversions by having a moment of silence for DIN 933 and DIN 931. I did this because the DIN 933 and 931 standards were formally withdrawn in 1986 and given a five-year transition period, which was expected to end in 1992. Obviously, this has not stopped the pervasiveness of DIN 933 and DIN 931 hex heads within the metric fastener supply chain. Any major master distributor stocking metric fasteners in the U.S. is bound to have some M10 X 40 DIN 933 hex heads in class 8.8 steel sitting in stock that they imported by the
hundreds of thousands from Asia, but what they may not have (at least stateside) is that same hex head to the ISO 4017 standard. So, even though the DIN 933 standard has been formally withdrawn and replaced by the ISO 4017 standard, over thirty years later, this change has done little to change demand.

Fortunately for hex head bolts, DIN 933 and ISO 4017 are fully interchangeable at all but those four diameters: M10, M12, M14 and M22. This interchangeability does not exist for all DIN to ISO crossovers though. Some DIN standards are actually harder to source than their ISO counterparts and they are not necessarily interchangeable for all applications. Take that M10 X 40 hex head for instance. As mentioned, M10 is one of the diameters in which the dimensions are different. Due to having a different WAF (width across the flats), some applications may not be able to accept the DIN 933 hex head and therefore must look to source the ISO 4017 counterpart.

A few months ago, we released a DIN to ISO conversion guide, which can be found on the Eurolink Fastener Supply Service website or in posts on our social media pages. While other guides exist, some that are even more detailed, I had not found one that covered as many product lines as the one we created. This is reasonable as they are usually released by companies for their own product lines only, therefore I found them incomplete as companies only have incentive to provide conversions for the products they carry.

On the other hand, at Eurolink, we are not just a commodity importer, but rather a sourcing service, therefore (while we certainly have particular product lines that we favor and stock) we are not limited to any predetermined availability. In other words, if you need a metric fastener, we can most likely find some options for you, therefore while we easily tout access to over 100,000 C-class fasteners, it is difficult to estimate the true, uppermost range of products available within our network.

With procurement teams sourcing fasteners for increasingly complex and globalized projects, it makes sense that such teams would rely on Eurolink’s services to decrease the demand on their teams and/or expand their product ranges. It is within that vein that Eurolink operates. We do not supply OEMs directly, rather we supply the stocking distributors that supply those OEMS. Our niche’s position in the supply chain uniquely positions us. Rather than working with engineers, we are usually working with sourcing specialists, account managers and sales representatives. These positions do not always need all of the details, but they do need references that they can refer to quickly as they handle their workflow volume. Enter the Eurolink DIN-to-ISO conversions chart.

While this conversion chart is a useful resource, for sake of simplicity, the one-page chart could not incorporate nuances like the interchangeability of the standards or detailed dimensional differences. As stated, some conversions are not interchangeable. Circling back to our DIN 933 to ISO 4017 conversion example, particularly at that M10 diameter, the difference is small, in this case literally 1mm, with DIN 933 having a WAF of 17mm and ISO 4017 having a WAF of 16mm, but consider the implications if an assembly line operator or machine has a wrench tool that is specific to the 16mm WAF requirement. I think you can read between the lines on that one.

Other conversions are not so minute. Unfortunately for me, early on, I once made the mistake of thinking that I could provide a customer with an ISO 10642 when they requested DIN 7991. Of course, we corrected the mistake quickly, but sourcing the DIN 7991 fastener at was not simple and was quite a bit more expensive than it’s ISO 10642 counterpart, therefore we had to take a loss on that sale. For whatever the reason, some conversions have been embraced by the industry, therefore it’s not always the case that the ISO version of a fastener is going to be the harder to find fastener, sometimes it is the DIN version that can create headaches for procurement.

Honestly, I would recommend that anyone involved in procurement in the supply chain have a copy of our conversion chart on the wall by their computer for quick reminders, but (especially early on, as you are learning the differences) that they also download and keep handy the document created by Würth Industrie Services (Germany) titled “Fasteners: Differences between DIN – EN – ISO standards”. This document can be found with a quick Google search and is one of the most helpful documents for making decisions about DIN to ISO conversions. It is not all encompassing, but it is a very good resource. 

As I am a few months into my second year creating educational resources for the industry, I have decided to dig even deeper into the standards and begin sharing even more nuanced explorations of these standards in my second “season” of VLOGs. Some conversion differences, as already explained in previous videos, are not only dimensional, but can include differences in the material themselves or the processes used to ensure consistency. My discussion in a recent episode of Fully Threaded Radio with Carmen Vertullo, in which we apparently “solved” an industry mystery, hints at such nuance.

If you ever have any questions related to this subject or an inquiry for such fasteners contact me or one of my very knowledgeable and helpful colleagues over at Eurolink Fastener Supply Service.

Click Here to download our DIN to ISO Conversion Chart.