Tag Archives: Tightening

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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Tension Control Bolts

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Reprint from Hardware & Fastener Components Magazine, Vol. 51

What are Tension Control Bolts?
Tension Control Bolts have a domed head, body, threads, and a splined tip known as the Pin Tail. (See Figure 1) Tension Control Bolts are part of the structural bolting family given by ASTM F3125. Like the other structural bolt variations, these come in two different types, regular and weathering steel and two different strength grades, 125,000 psi and 150,000 psi. The 125,000 psi version is considered Grade A325 and marked as A325TC or A325TC depending on whether it is Type 1 (regular steel) or Type 3 (weathering steel), respectively. The 150,000 psi version is considered Grade A490 and marked as A490TC or A490TC depending on whether it is Type 1 or Type 3, respectively.

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An Overview of Fastening Tools – Understanding Your Options

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Reprint from Hardware & Fastener Components Magazine, Vol. 44

Several days before Christmas of 2016, a truck driver was passing through Chicago on one of the primary expressways. All of a sudden he noticed a large obstruction in his path and swerved his truck to miss it. Unfortunately, in this maneuver he clipped an adjacent vehicle sending him out of control, flipping his truck on its side, breaking through the center concrete divider, and hitting an on- coming vehicle. Sadly, the truck driver lost his life in this tragic accident.

Accident scene investigators would later determine that this accident was triggered by a wheel that had separated off of another truck and was lying in wait on the roadway for an unfortunate victim. In answer to a spate of such incidents, in 1992 the United States National Transportation Safety Board (NTSB) sponsored a study to examine the cause and frequency of wheel separations from large Class 8 trucks. Shockingly the study determined that there are between 750 and 1050 such reported separations on U.S. roadways every year. That amounts to two to three every day. The study went on to find that the leading cause of such separations was improper nut and stud tightening during the installation or reinstallation after maintenance of large truck wheels.

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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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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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