In response to a changing global combat environment, today’s defense industry is transitioning in many cases to aluminum structures; leveraging weight savings that provide soldiers with agile vehicles with which to execute their mission. While aluminum provides substantial weight savings over steel, it’s also much softer than steel, leading to the use of stainless steel or titanium “threaded inserts”. Threaded inserts serve as a wear-resistant interface between the aluminum structure and the hardened steel bolts used to attach components to the structure.
The ‘Fredsert’ is a threaded insert patented by the General Dynamics Corporation in 2001. Fredserts were initially designed for the Expeditionary Fighting Vehicle (EFV) by an Engineer named Fred Wheeler. Fred designed the product to meet the unique demands of the EFV program, which included a water-tight seal, solid locking to prevent back-out, corrosion resistance in extended saltwater exposure, and the ability to be easily removed and replaced in the field. The Fredsert has simplified vehicle design, improved producibility and reduced program logistical costs. Today there are nearly 4,000 Fredserts incorporated in each EFV, and the use of Fredserts has expanded to a number of other applications.
The Fredsert geometry is effective in that it combines a tapered thread profile, full thread engagement, cutting flutes and a flanged head. These unique features deliver a combination of friction fit and material compression designed to resist vibration, tensile loading and shear loading in the most demanding heavy-duty applications. This new technology has fostered new attachment concepts, reducing the total number of fasteners, while at the same time introducing flexibility in vehicle assembly operations, reducing overall assembly costs. Logistical support costs have been reduced as well, since removal and replacement of the inserts in the field is drastically simplified.
One of the most unique features of a Fredsert is that it doesn’t permanently lock into place. Instead, its patented geometry causes it to “break away” at approximately 80% of the installation torque value, allowing it to be quickly and easily removed and replaced using the same equipment. Field removal and replacement of commercially-available inserts such as Keenserts and Rosans, on the other hand, increase logistical costs since the inserts must be drilled out due to their mechanical locking mechanisms. This becomes especially difficult if the insert is installed in a large structure or a tight enclosure because access and rigidity are limited.
Another feature that sets Fredserts apart is the fact that Fredserts are available in Titanium as a standard product, in addition to those made from Stainless Steel. This is a very unique and important advantage, as Titanium Fredserts deliver weight savings of 40% over Stainless Steel inserts of the same size. Titanium inserts from other leading insert manufacturers, however, are either not an option or they are quoted with an extremely high price and long lead time.
A third key benefit that differentiates Fredserts from the competition is the fact that they create a 100% watertight seal without the use of a thread locking agent, such as Loctite. The combination of a tapered thread profile, 100% thread engagement, and a flanged head deliver a perfect seal on the OD thread of the insert. “Blind” Fredserts also deliver a watertight seal on the ID thread, because the ID thread bore doesn’t break through the bottom of the insert.