Fastener Engineering

Is There Value in Application Engineering?

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Reprint from LINK, Summer 2021

I began my career in the fastener industry over thirty years ago as an Application Engineer. This was a great place to start, and, perhaps, the most cherished time of all my years in the industry. I suppose that Application Engineering can mean different things to different people, but within the fastener realm this role is pretty universally understood as an interface which works with the customer to provide the best fastening solution. This not only means choosing the correct fastener but also the related joint design, fastener heat treatment, finish, packaging, and any number of other design or process related decisions.

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A “Galling Development” – What Every Distributor Should Know about Thread Galling

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Reprint from LINK, Spring 2021

A number of year’s back I was engaged by a Midwestern distributor to review an application problem that had intermittently plagued one of their more important customers. Upon meeting with their customer, I learned the problem occurred during the assembly of a stainless steel Nylon insert lock nut to a like stainless steel screw. Although this was a sporadic problem, when it occurred the customer would experience assembly difficulties like nuts that were very hard to turn, nuts that reached installation torque levels before seating, and in the worst cases, nuts that became totally frozen (seized) in mid-run down position, often breaking the screw in torsion.

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The Importance of Controlling Joint Tightening

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Reprint from Hardware & Fastener Components Magazine, Vol. 43

On December 23, 2016 a fatal crash occurred on a busy Chicago highway. A large tractor trailer truck hit a car, flipping over, and crashing through the center median hitting on-coming traf c. What could have been a horrendous holiday tragedy was limited only to the driver of the truck. Unfortunately, even one fatality is too many, especially if it is due to an entirely preventable cause.

Early reports claimed that the crash was caused by a wheel separating from the truck. It was believed that this caused the driver to lose control resulting in the subsequent chain of events. After accident reconstruction, however, it was determined that the truck driver actually hit a wheel (tire and rim) that had separated from another truck and was lying in the roadway.

Now what does this accident have to do with fasteners?

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“Staying Put” – About Keeping a Threaded Fastener in-Place

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Reprint from Fastener World Magazine, Vol. 170

About twenty years ago I was travelling quite often between the United States and Europe. To make sure that my luggage arrived in one piece I purchased a medium sized, hard-sided suitcase. As I unpacked the suitcase at the conclusion of every trip I would find a loose screw or two rolling around the bottom of the suitcase. To be honest, I never could figure out exactly where these screws were coming from or how so many could come loose without the suitcase falling apart, but they clearly had loosened up from the suitcase and come out during travel. I began to worry that I was only one trip away from a major catastrophe with my bag, so that today I use a different suitcase when I travel internationally.

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Understanding Fastener Strength

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Reprint from Fastener World Magazine, Vol. 174

To understand why fasteners are manufactured to different strength levels, one must first understand how a fastener is intended to work. To work properly, a fastener must possesses some elasticity and stretch as it is tightened. For many this is counterintuitive because, for example, a large 1” diameter steel bolt hardly seems like an item that would stretch. However, stretch it must if it is going to function the way it was intended.

Figure 1 illustrates a demonstration that one can use to understand the behavior of a bolted joint. To conduct this demonstration, one places their thumb, index, and middle fingers together, wraps a wide rubber band twice around, and then opens their fingers against the resistance of the rubber band. In the second part of the demonstration a third wrap of the rubber band goes around the fingers and reopening the fingers is, once again, attempted. Individuals attempting this demonstration should notice that with the third wrap in-place the rubber band is much more highly stretched and it becomes significantly more difficult to open the fingers.

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Pre-load: Part II – Tightening Strategies

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Reprint from Fastener World Magazine, Vol. 151

In Part 1 of this series we explored the fundamental concept of Pre-Load and what this means to the fastened joint. Although understanding this concept is a fundamental fastener engineering tenet, one likely cannot stop there and is led to ask the question of how one practically achieves this Pre- Load in the bolted joint. This is where the subject of “tightening strategies” arises. Before we look at the different tightening strategies, let’s briefly review the concepts of pre- load and torque-tension.

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Pre-load: A Primer

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Reprint from Fastener World Magazine, Vol. 150

In the world of fastener engineering, all too often the joint designer gets focused on the wrong things; torque, locking mechanisms, degrees of rotation, and a number of other sundry items, at the expense of focusing on the most important element, joint tension. Of course, this is understandable since torque and angle are the fundamental measures the industry uses in tightening critical joints. Additionally, torque and angle are easily measured and reasonably easily controlled. However, it is the tension that holds the joint together, which makes
it supremely important both at installation and over the service life of the joint. Therefore, it is critical that the joint designer generates sufficient tension so that the joint can perform safely immediately after tightening, but also years down the road after relaxation and other diminishing effects have acted on the joint.

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Reflections on Torque

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Reprint from Fastener World Magazine, Vol. 169

In the fastener world there is perhaps no more commonly used expression than “torque-tension”. So common is this term in fastener circles that it is thrown out in everyday conversation and accepted by all at face value. One can understand this, as finding the perfect “torque-tension” behavior is the Holy Grail of fastener engineering. Unfortunately, like many technical terms that have been elevated to everyday usage, the vast majority of those hearing it fail to understand the fundamental principles it is meant to describe. Take for example a recent blog posting I encountered. It was addressing the question of which is more important, torque or tension. Although it was a well-intentioned posting, even the most novice fastener engineer realizes that the bolted joint is wholly dependent on properly achieved tension. Like many of the technical terms that make up the modern lexicon (such as fusion, heat treating, Xeroxing, and hundreds of others), the term “torque-tension” is broadly used by purveyors and users of fasteners, but generally poorly understood. So let us investigate this topic and see if we can find some simple answers into what “torque-tension” is all about.

joint is wholly dependent on properly achieved tension. Like many of the technical terms that make up the modern lexicon (such as fusion, heat treating, Xeroxing, and hundreds of others), the term “torque-tension” is broadly used by purveyors and users of fasteners, but generally poorly understood. So let us investigate this topic and see if we can find some simple answers into what “torque-tension” is all about.

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Miniature Thread Forming Screws for Plastics and Light Metals for Electronics Applications

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From Fastener World Magazine, May/June 2014, Volume 146

As handheld electronic devices have gotten smaller and lighter, the fasteners that hold them together have had to follow suit. Although miniature metric and imperial machine screws have been used in eyewear, watches, and cameras for many years, it is only relatively recently that very small variants of thread forming screws have become commonplace. It is impossible to explain why this is the case, but probably stems from the fact that thread forming in plastics and light metals is a practice that has itself only recently gained universal acceptance.

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Strategies To Mitigate Fatigue Failure in Fasteners

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From Fasteners Technology International, August 2013

Although component failures have probably been around for as long as man has been putting things together, it wasn’t until the early to mid nineteenth century that engineers began studying the progressive failure mode that we know today as fatigue. Although highly undesirable, fatigue is a relatively common failure among fasteners and regretfully can lead to some dramatic and even life-threatening consequences. A great deal of progress in understanding fatigue has been made since the nineteenth century, and yet there is still much to be learned. Fortunately, enough is understood today that specific strategies and practices can be employed when a bolt or screw is designed in an application at risk of fatigue failure. This article will look at the basics of fatigue in fasteners and preventative measures that can be adopted to reduce the risk of failure and improve the durability or life of the fastener component.

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