Design engineers and fasteners 15 June 2020

By Peter Standring, technical secretary, Industrial Metalforming Technologies (IMfT)

Whilst only a few people could ever claim to have been educated in design, it rarely prevents the majority from exercising their opinions. Given the range of ‘professional’ design creations, from landmark buildings to the often outlandish, it is clear that money and creativity do not always equate to common sense.

In the industrial and commercial world, some design decisions are obscured by matters that are only evident to those who assess them in a particular way. Take for example the Fiat Multipla car. Although it had many novel, very useful customer features, it is generally recognised as being one of the ugliest vehicles ever produced.

However, that didn’t prevent the world’s other motor manufacturers giving it accolades for its design. Why? Because by using a steel spaceframe and composite panels it was possible to have an annual breakeven build number of just 30,000 vehicles. In an era before assembly line sophistication made it possible to build multi model/variants at the same facility, OEM’s had low number cabriolets, station wagons, sports models, etc, produced by tier half suppliers. For Fiat to design an SUV with such a low breakeven number was recognised and heralded within the automotive industry as a genuine success.

Despite the occasional one off design crazes that sweep the world, promoted largely by social media, the most effective and successful designers are those who are able to link their knowledge with the experience they have gained working in the field. In many cases, this will be specific to the area in which they are specialist. In others, a wider, more general appreciation of what is required will pertain. Both have equal significance and the designs they produce will be recognised in terms of desirability by what they bring to the table. However, in a professional world, any professional is only as good as the message he or she carries. If it is not up to date, then, by virtue of that fact, it will not be complete.

It is this simple fact, coupled with the breadth of knowledge required, which should give all design engineers some thoughtful moments. Good as many people believe they are, it is a recipe for disaster to consider we know it all. From gambling to conflict, those who are convinced they are right always experience the hardest fall.

‘Measure twice and cut once’, is an axiom all design engineers should have tattooed inside their eyelids – particularly when working in an area that might be outside their comfort zone. Fasteners are one such area where this axiom is often very true. Sure, the fastener industry has specialist design engineers whose role in life is to create/manufacture devices to hold other things together. OEM’s will (should) have design engineers to advise on fastener identification/usage within the company. For instance, General Motors began back in the previous century to develop a ‘de-proliferation’ (standardisation/rationalisation) programme to reduce cost and maximise the efficient use of fasteners.

However, for the vast majority of design engineers, in whatever industry they serve, fasteners will not be their primary concern. That is despite the fact that in engineering there are very few single items/ standalone objects (notwithstanding those produced by additive manufacturing techniques). Therefore, the need to have a sound working knowledge of fasteners is fundamentally important. So, the question must be asked, from where would this information come?

Educating designers
In today’s market driven world, words say it all. The term ‘engineering’ in some cultures is highly regarded, in others it conveys an image of an oily rag. For educational bodies to hit the market sweet spot the term ‘engineering’ must be defined.

Aerospace, automotive, chemical, electrical, electronic all reflect a commercial sector. Cutting across these are a spectrum of specific and general areas of engineering relating to metrology, materials, manufacturing, design, etc. Within these are sub sectors that focus on particular and often ‘trendy’ career opportunities. Product design courses are typical of these, linking art, marketing and fashion with engineering, manufacture and materials. In all such courses, the time demands on the curriculum often leave little opportunity to consider much more than an overview of fasteners.

The same situation will be found in most classroom-based ‘engineering’ courses. Given the often safety critical and functionally significant importance fasteners play in every aspect of life this is a surprise. Through no fault of their own, today’s digitally interactive, software-based student is often provided with a drop-down menu of options to select. Without the benefit of ‘real world’ practitioners on hand to pass on advice, the inevitable can and often does happen. A prime example is the youngster, who when attempting to increase the compression ratio of an engine, attached steel discs to the heads of the pistons using self-tapping screws and was surprised to find they melted.

The EU has just announced that it will seek a parliamentary decision on making all smart phones and tablets sold inside the community repairable. This is in addition to the Right to Repair Directive for White Goods, which comes into force in April 2021. The legislator’s purpose here, to help reverse the OEM tradition of ‘design for obsolescence’ and zero disassembly – thereby extending product life and saving primary resources. Under such regulations, permanent bonding by gluing, welding/brazing, as well as mechanical cold forming, will all need to be replaced by the use of removable fasteners. So again, we might enquire, where will the designers of tomorrow learn about such matters?

Fastener information
One thing the fastener industry has going for it is a second to none portfolio of national and international standards on which its successful use has been based and is regulated.

In an age of computer generated graphics, virtual reality, etc, it is difficult to be surprised at the practicalities of real life. Tallest buildings constantly sprout up only to be relegated as such within a short period. Before the ‘Digital Age’ kicked in, it was a significant achievement to design and build something that could repeatably measure a millionth of a metre. Today, with the discovery of graphene, folks are literally working at the atomic level to fasten things together. So, what resource is available to the design engineer to gain a practical knowledge of fasteners?

The problem is not a new one and was recognised some years ago by NASA, who created a manual as a source of reference to which all their staff could have direct access and which would provide a comprehensive review of most fastener matters. In recent times, the freely available Fastener Design Manual (NASA) 1990 has been put into digital format by commercial entities and can be downloaded online, purchased as a hardback copy or accessed as a design course on YouTube.

All industrialised nations have their own national standards for fasteners, defining, specifying and inspecting them, etc. A first port of call for this knowledge would be a review of the International Organisation for Standardisation (ISO) Handbook for Fasteners and Screw Threads (1998). This comes in two volumes and presents a general reference and product standards.

As would be expected, national standards for fasteners are similar. However, because of the diversity of fastener element types, identifying, obtaining and assessing this information can be both time-consuming and complex.

Many fastener manufacturers have posted technical product information on their websites. These are often designed to educate and train potential users who in turn could become customers of the product.

Many academic lectures and series of lectures are currently available on YouTube providing often detailed analysis of fastener selection, assessment and application. Additionally, internet searches for fastener-based trainers and consultants will produce numerous positive results over and above the information sources offered by fastener manufacturing companies.

Trade bodies and specialist institutes are also to be found in many countries and these are generally linked with continental and global fastener bodies. Table One lists many of these sources and provides an introduction to those interested in the design and application of fasteners.

Conclusion
Given the widespread availability of fastener information from multiple global sources, awareness, or lack of it by designers, is evidenced in the design choices made. However, the best designs may not be based on selection alone. If this were so, little forward progress would be made. For those who are really good at what they do, the goal is to create tomorrow.

The best example I am aware of in regard to the use of fasteners was in an automotive engine. Here 22 different fastener types were employed requiring multiple different coated surfaces to deal with the various environmental conditions they faced. Having studied the problem, the design team instituted a research programme and found one surface coating that could satisfy all the conditions fasteners experienced within the engine. They also rationalised the 22 fastener types down to 6. The result, higher volume of standard parts, significant cost reduction – whilst satisfying both quality and function.

It is an often stated fact that 95% of all manufacturing costs occur at the design stage. The selection of fasteners at the design stage can really make a significant difference – either positive or negative. Careful selection will satisfy the need, a thoughtful assessment of the problem could provide very much more.

Primary sources of fastener design information

General
Fastener Design Manual (NASA) March 1990, R. T. Barrett

Standard Handbook of Fastening & Joining 3rd Ed. 1997, R. O. Parmley

Metals Handbook
Vol I, Tenth Ed. Threaded Steel Fasteners
Vol II, Failure of Mechanical Fasteners

SAE, Fastener Standards Manual 2009 Ed.

Standards
ISO Standards Handbook
Vol 1, 1998 Ed. 4, Terminology and nomenclature, general reference standards
Vol 2, Product standards

Associated National Standards for Fasteners (all major countries)

Trade bodies
European Industrial Fasteners Institute (EIFI)
Confederation of British Metalforming (CBM)
Industrial Fasteners Institute (IFI) USA
The Fastener Institute of Japan (FIJ)
Taiwan Industrial Fastener Institute (TIFI)
Fastener Industrial Coalition (FIC) USA
Korea Federation of Fastener Industrial Cooperatives (KFFIC)

 

Will Lowry Editor t: +44 (0) 1727 814 509

Will joined Fastener + Fixing Magazine in 2007 and over the last 12 years has experienced every facet of the fastener sector – interviewing key figures within the industry and visiting leading companies and exhibitions around the globe. Will manages the content strategy across all platforms and is the guardian for the high editorial standards that the brand is renowned.