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For several decades now, experts across the fastener industry have dedicated considerable time and effort to improving the overall design and, most importantly, dependability of their products. But even when you factor in the years of hard work that has been devoted to perfecting fasteners, very little of that work contributes to or guarantees the reliability of the joint.

When selecting your fastener, it is important that you first understand the mechanics of how a threaded fastener sustains loading and how specific tightening procedures also factor into the equation. There are a number of factors to consider in the design of bolted joints, in addition to a basic understanding.

Whereas a loose or untightened bolt would fail in a matter of seconds, a bolt that has been fully tightened would be capable of surviving when used as part of an application. Though you might think otherwise, a tightened bolt just sustains a small portion of a load once it has been applied the joint, rather than sustaining the full effect.

This concept can often seem in opposition with common sense, but understanding that the bolt does not sustain the full effect is of paramount importance. Weight applied to a nut loose on the bolt leads to a full increase in force on the bolt shank. When the same weight is applied to a tightened nut, the force on the bolt shank increases, but the increase is a fraction of the full effect.

Thus, no significant load increase applied to a fastener would be sustained, that is until the load exceeds the fastener’s preload. Hence, the importance of understanding and factoring in preload.

With the use of a special fastener, one can gain a better understating of the load transfer mechanism involved in a bolted joint.

To learn more about the importance of bolt preload, contact Bossard at ProvenProductivity@bossard.com.

Using the proper torque is an important part of a reliable bolted joint. Insufficient torque can lead to the fastener being loosened by vibrations while excessive torque can cause stretching and breaking of bolts. Once the proper torque has been determined for a joint, it is a good practice to perform periodic audits to ensure you are reaching your targets.

There are three general methods of testing to ensure that the proper torque has been applied.

First Movement Test

This particular method requires the use of a torque measuring tool, and is best used to determine residual torque. Residual torque is the amount of tension leftover in a joint after fastening a threaded fastener.

First, mark the tightened fastener and surrounding application. Slowly apply force to the tool, in the same direction used to tighten it, until the first movement in the fastener is noted. The reading recorded should provide you with an idea of the original torque applied to the joint.

Loosening Test

This method is similar to the first, with one fundamental difference. Instead of tightening the fastener, this test applies the torque in the direction that loosens the fastener. Should you choose this method, you’ll record a torque reading once the fastener breaks loose, and that should give you an accurate indication of the approximate torque applied to the joint.

Marking Test

For the third and final testing method, mark the surface of the tightened fastener and continue that mark onto the surface that is being clamped. Then, loosen the fastener and retighten until the marks are aligned. This allows you to measure the torque required to return the fastener to its original location, and thus the original torque applied.

Knowing how to properly utilize each method is equally important to understanding the importance of such tests. To learn more about torque and methods for measuring it, contact Bossard at ProvenProductivity@bossard.com.

Everyone wants the tool that is going to streamline their processes. Fortunately, Bossard’s semi-automatic fastening system utilized with Speed Rivets is one of those invaluable tools.

Speed Rivets are designed for a rapid installation, perfect for quickly fastening different materials and thicknesses. Electronic applications, vehicle construction, household appliances and metal cabinets are among the different applications that Speed Rivets are ideal for.

How It Works

Speed Rivets are pre-loaded on a mandrel, where they’ll be introduced into the nose of the riveting tool for continuous fastening up to 70 rivets per minute.

Tool actuation pulls the mandrel through the rivet, expanding it within the hole. This provides high clamping capability and secure joints. With controlled wear and tear of the disposable mandrel head used for the rivet expansion, rigorous clamping of all rivets is achieved.

The standard Speed rivet is capable of achieving high clamping strength thanks in large part to the formation of its closing head. Multi-speed, grooved and other types of Speed Rivets are also available depending on your material requirements.

Why Semi-Automatic Fastening?

The benefits of using semi-automatic fastening with Speed Rivets are myriad. First and foremost, semi-automatic fastening reduces the loading time of rivets in guns manually. With Speed Rivets, the need for reloading after each rivet is also eliminated.

The tools required for installation can be pneumatic or hydro-pneumatic, and can be custom-made to suit your assembly requirements. Due to the increased installation speed, you’ll see a substantial decrease in the amount of overall time required for assembly.

Few solutions available on the market allow you to increase the speed and efficiency of your processes while also maintaining both the quality and security of your products. Speed Rivets and semi-automatic fastening   the rare advancement that does it all. To learn more about the benefits of Speed Rivets, contact Bossard at ProvenProductivity@bossard.com.

To create fasteners through hot forging, the metal is heated before the forging process during the forming process. Cold forming is quite the opposite. This process, which became commonplace after World War II, is where the metal is shaped at room temperature, as opposed to being heated. (more…)

When deciding what size or type of fastener best fits your needs, it is important to know the strength of the fasteners you’re choosing from. This can identified by the grade or property class associated with the fastener. Inch fasteners, which are more common in North America, will have a grade or a rating from the American Society for Testing and Materials. Property classes are used for metric fasteners. (more…)

Why Loosen?

Loosening fasteners have been an issue for decades. Because a fastener coming loose can often lead to an accident, it is important to understand the possible factors that could contribute to the loosening of a fastener.

Typical applications for fasteners are in clearance holes, and the tightening of the fastener helps maintain the structural integrity. If loosening occurs, the preload is reduced or eliminated completely, resulting in structural failure. (more…)