Fastener Engineering

The Art of Thread Forming Fasteners, Part Two – Thread Forming Into Plastics, Light Metals, and Steels

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From Fastener Technology International, June 2013

In Part One of this two-part series, we looked at the general principles of thread forming that apply uniformly regardless of screw or material type. In an ideal world, “one size would fit all” and any screw could be universally used in any material. However, anyone that has ever tried to thread a standard sheet metal screw into polycarbonate or into a thick steel plate might attest to catastrophic results. Why? Quite simply, the fastener being used was never designed to perform in these materials.

Therefore, the first ground rule that any Fastener Engineer or Designer must employ is to choose a fastener that was designed to work in the material and the situation intended. There is some excellent fastener technology that works well in the applications it was designed for, but not so well with other materials. So it is incumbent on the Designer to know as much as possible about all aspects of the joint and not to simply assume that because the fastener works well in thread forming such-and-such a material, that it will work well in a different one.

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The Art of Thread Forming Fasteners, Part One – General Principles

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From Fastener Technology International, April 2013

One of the roles of every Fastener Engineer or Designer is to look critically at each new problem and develop an elegant solution that is as simple in form as it is effective in practice and efficient in cost. That often means using the minimal amount of resources to gain the maximum achievement. The “art” of thread forming fasteners provides a powerful tool in the industry arsenal to achieve such results for customers.

When it comes to fastened joints made up of a threaded fastener and some type of nut member, there are really only two varieties, those that start with a nut member thread already in-place and those that depend on the threaded fastener to create its own mating thread. A great deal of technical information can be found where both screw and nut member are threaded, but far less is available and understood on those where the nut member thread is formed by the screw itself.

This two-part article series will attempt to remove some of this mystery. Part One will explore the basic guiding principles of thread forming. These are principles and behaviors that are true regardless of the screw or nut member material. When I am done, it is my hope that the reader will have gained an appreciation for how thread forming works and the general areas of concern for the Fastener Engineer when he or she designs such a joint.

Part Two will explore the more specific and specialized cases of thread forming into thermoplastic, light metal and steel materials. Although not the only materials available for thread forming, these three categories represent the majority of areas where thread forming fasteners are utilized today.

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Doing it Right the First Time

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Designing the right joint or fastening system up-front with some value and application engineering techniques in the early design stages is extremely important.

From Fastener Technology International, August 2012

In the 1998 movie, “Armageddon”, as he is being strapped into a space capsule atop a rocket, Rock Hound, the character played by Steve Buscemi utters this line to Harry, the character played by Bruce Willis, “Hey Harry? You know we’re sitting on four million pounds of fuel, one nuclear weapon and a thing that has two hundred and seventy thousand moving parts built by the lowest bidder. Makes you feel good, doesn’t it?”

 In my opinion, this ranks as one of the most humorous lines from Hollywood in recent years. But unfortunately, one that expresses, at its core, an attitude that all too often seems to prevail among even the best and most enlightened users of fasteners.

 How often have you heard that, “it’s only a screw, nut or bolt” or found yourself in a tense situation trying to make or locate a fastener because your customer failed to appreciate the engineering complexity, time or dollar constraints associated with making or procuring the right one?

 Naturally, most of the readers of Fastener Technology International probably have a healthy respect for how much engineering goes into specifying, designing and manufacturing the right fastener for a specific application. You realize how critical a fastener can be to the overall success or failure of a customer’s project.

You can probably cite multiple instances of customers that have failed to adequately consider the design of the fastened joint or waited to the last minute to choose the proper fastener, and then had the audacity to wonder why your company cannot support them. How often have these delays or oversights ultimately cost the customer precious resources and you “reputation points”?

 Fortunately, no one needs to find themselves in this predicament. With proper education, communication and the latest in application and value-engineering tools, many of these pitfalls can be avoided. Generally, it doesn’t take a significant investment of time or resources to work with a manufacturer, authorized distributor or knowledgeable party to conduct value and application engineering services early in the design cycle and eliminate much of this frustration on the backend. In most cases, it is clearly evident this early investment can pay significant dividends later in the design cycle.

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