Which Threaded Inserts are Best for Metal vs. Plastic?

Threaded inserts are one of the most versatile types of fasteners and can be used in any material that needs to accept a threaded bolt. As with other types of fasteners, threaded inserts come in various configurations, designs, and materials to accommodate different types of jobs. There is a big difference between the types of threaded inserts used to add threaded fasteners to metal and those needed to add threaded fasteners to plastic because the characteristics of the work materials are so different.

When we refer to threaded inserts, we are talking about sleeve inserts that are designed to fit in a pre-drilled hole and have internal threads to accept a bolt or threaded fastener. Rivet nut inserts are probably the most common and are designed as blind inserts that can be installed from one side. To keep them securely in place, they can be bulbed on the blind side, or the blind side can be drawn in or collapsed when the bolt is screwed in. 

Eurostyle threaded inserts come in geometric shapes, such as hexagonal, that keep them from turning in the hole. Molly jack inserts are slotted so they collapse on the blind side of the joint. Wellnut inserts are made of rubber to form a watertight and vibration-resistant seal.

The advantage of using threaded inserts is that they provide a firm foundation for a bolt or screw-in fastening, and the fastener can be unscrewed and screwed in again to make repeated assembly and disassembly easier.

Threaded Inserts Need to Match the Materials Used 

Each type of threaded insert has unique applications and is designed to be used with different types of materials. In the case of metals and plastics, for example, you have two types of materials with very different characteristics. Metal is hard, so it requires a threaded insert that is secure, won’t pull out, and won’t turn in the hole when a fastener is screwed in. Plastics are softer and more brittle, so they require a different kind of insert that won’t turn but also can absorb the shock of installing a threaded insert, especially in a factory or assembly line setting.

You can imagine the various applications for threaded inserts. For metal assembly work, you need a threaded insert that is hearty and can stand up to the stress of whatever metal assembly you are constructing. For example, you may need a threaded insert to attach tubing or metal housings. In addition to threaded inserts, there are stud-style inserts that can be secured in pre-drilled holes to accept nuts and are commonly used for metal fastenings. 

You also can use threaded inserts to connect different types of materials, such as screwing wooden surfaces to metal tubes or surfaces. They also are frequently used to repair stripped threads in pre-drilled metal holes. For example, consider how valuable threaded inserts are to automotive manufacturing and auto body repair, providing a means to securely attach and disassemble parts.

Threaded inserts are also commonly used with plastics, especially for consumer electronics and related applications. Mobile telephones, tablets, computers, and other electronics are assembled using threaded inserts that make it easy to remove panels, secure components, change out circuit boards, and so on. Threaded inserts for plastics are also commonly used in aerospace applications, transportation, recreational equipment, and other applications where plastics need to be securely fastened together. They are even used in medicine for prosthetics manufacturing and medical equipment.

Threaded Inserts Are Designed to Be Versatile

There are different brands and types of threaded insert fasteners that you might consider:

• Thick wall inserts, sometimes called nutserts, have been used for metal assembly applications for some time, starting with the original design used in aircraft manufacturing in the 1930s. Nutserts are high-strength and come in different sizes, thicknesses, and designs. Avdel’s threaded nutserts are great for metalworking because they have a 360-degree swage for an extremely secure fit. AVK’s knurled nutserts are useful for fiberglass and thicker plastics because they won’t pull out.
  
  
• Slotted-body inserts are designed to create a bulb on the blind side and are often used for plastics and soft materials because they can be installed quickly and create a firm, lasting insert. Pre-bulbed shank body inserts from Atlas, Avdel, AVK, Goebel, Marson, and other manufacturers are available in steel, brass, zinc, and other materials. These inserts are ideal for softer materials such as plastics because they won’t turn or pull through.
  
  
• Threaded rivet nut inserts or rivnuts are very useful for attaching metal parts and housings, as well as connecting different types of materials such as metal and fiberglass. They are commonly used with thin metals and to repair stripped threads. AVK and Atlas rivet nuts, for example, are available in tubular, hexagonal, and flanged designs for multiple applications.

There are threaded inserts in configurations and materials for any type of job. Choosing the right type of rivet nut insert can be tricky, especially when dealing with different types of metals or softer materials such as plastics. You want to make the right choice to be sure the joint is secure and will last no matter how often you have to insert and unscrew the fastener. To make sure you choose the right threaded insert, consult an expert such as one of the professionals at Bay Supply. To get started, you can download our e-book, The Essential Guide to Threaded Rivet Nut Inserts.