How to Choose the Right Threaded Insert for the Job

Whenever you are working with fasteners, you want to be sure you have a strong, durable rivet or bolt that is suited to the job. Blind threaded inserts are among the most versatile types of fasteners, and there are thousands of types from which to choose. Choosing the right threaded insert depends on the nature of the materials you are working with and the application.

What’s a Threaded Insert?

A threaded insert is a sleeve with a threaded interior that can accept a bolt or threaded fastener. The insert can have different dimensions, be made of different materials, and come in different configurations or tooling; its design will hold fast in thin or soft materials, making the threaded fastener secure.

If you have devices that need to be disassembled and reassembled or that use particularly soft materials, threaded inserts offer a number of advantages, especially if the connection is load-bearing. Flexible plastics, for example, have difficulty holding a threaded bolt because the threads in the tap hole aren’t durable enough. Rather than relying on threads drilled into the soft workpiece itself, a threaded insert gives you more strength and more versatility and tends to be more resilient over time.

Designed with Automation in Mind

Blind threaded inserts can be installed from one side, enabling faster installation, especially in a production line. They offer a stronger alternative to weld nuts and tapped holes, and they provide a stronger bond than self-tapping screws. In fact, threaded inserts are usually the strongest and least time-consuming fasteners used in any manufacturing setting, especially because they were designed for automation.

Threaded inserts have ribbed walls that offer greater strength under load. They can be used at virtually any stage of production, including after a workpiece is painted or coated, because they don’t require reworking once they are installed. That’s why blind threaded inserts have become so popular in applications such as aerospace, defense, transportation, clean energy, medical applications, and electronics.

There are a variety of different types of threaded inserts, each with a different design for a specific application.

• Rivet nut inserts, sometimes referred to as blind rivet nuts, can be installed from one side of a joint and have a counter-threaded interior designed to accept a bolt. Some rivet nuts will bulb on the blind side to create a solid connection. Others are designed to pull the rivet nut into the sleeve as they are tightened.
  Rivet nuts were first used to connect thick-walled materials in the 1930s, when RIVNUT® fasteners came into extensive use in aerospace manufacturing. When securing metal, thick-wall threaded inserts are often used. These are the most common types of inserts and come with both ribbed and knurled bodies, as well as smooth bodies in round, hexagonal, semi-hexagonal, and other shapes. They are made of different materials and come in different shapes, including large and small flanged heads, open and closed-end, and other designs.
  Thin-walled inserts came later in round, hexagonal, and square designs. These inserts offer added versatility, such as using sealant under the head or special plating for greater durability in harsh conditions.
  They also come in a knurled body design for a better grip on the material. For thicker fiberglass materials, such as those used in boatbuilding, knurled inserts are often used to minimize corrosion.

• Eurostyle inserts are round-body threaded inserts with semi-hexagonal, fully hexagonal, heavy hexagonal, or square body designs. They are available from a variety of manufacturers, including Avdel, Atlas, and Sherex Fastening Solutions.

• Slotted body threaded inserts are designed with gashes in the body that expand when the bolt is tightened for a firm connection. Slotted-body threaded inserts are commonly used for thin-gauged metals, such as aluminum. This insert has cuts along the body that come pre-bulbed to collapse on the blind side to secure the insert. There are straight-body and pre-bulbed body types from manufacturers such as Avdel, Atlas, Sherex, AVK, Goebel, and Marson.

Self-Tapping Inserts

Yardley self-tapping inserts are ideally suited for high volume assembly operations because of their easy, quick installation. Inserting a self-tapping insert is as simple as driving a self-tapping screw or tapping a thread. A drilled hole of correct size must be provided, driver tool is applied to insert, driver and insert are positioned over the hole, insert is driven (turned) home and the driver is backed off, leaving the insert installed. The insert cuts its own threads as it is driven into the base material. The methods listed below can be used to install Yardley TRI-SERT and FIBERSERT inserts.

Because it is driven by its internal threads, a different driver is required for each insert size. Thread cutting can be accomplished on either end because there is a lead in both ends of the insert. Alignment is important and the insert should be used with a hand tapper or a tapping head attachment on a drill press without a lead screw. For applications in recessed areas or close to walls or ribs, a Yardley Extension Driver may be used to facilitate installation. Inserts should be installed flush or below material surface. Thus, when one assembles a bracket and screw to the insert, the load is not transmitted directly through the insert but to the surface of the boss or the material in which the insert is installed. This is especially important where vibration is encountered.

The ultrasonic process converts electronic energy into high frequency mechanical vibration. The ultrasonic equipment operates from a normal 60-cycle line current and converts this to an output of 20,000 cycles per second. The output of the power supply received by the ultrasonic press that is similar to an arbor press in that there is a longitudinally moving arbor or tool. In this moving arbor, the oscillating electrical input of 20,000 cycles per second is converted to a mechanical vibration of 20,000 cps.

In the production operation, an insert is placed on the pre-drilled or pre-molded hole and the horn of the ultrasonic tool is pressed down on the insert. The horn transmits ultrasonic vibration to the metal insert and the friction from the vibration of the insert melts a thin film of resin at the metal-plastic interface. Pressure from the ultrasonic tool forces the metal insert into the hole until it is completely inserted. When the ultrasonic tool is removed, the melted plastic next to the insert solidifies and the insert is locked into place.

Since only a thin film of the resin is melted, residual stresses in a boss are minimized. Insertion time is relatively fast and the ultrasonic method is ideal for automatic, high production operations.

Cored or machined holes should be the correct size for the insert used. Excess melt squeezes out if the hole is too small. If the hole there is a reduction in stripping torque and pull-out force. Generally, the boss diameter should be twice that of the insert diameter. A larger boss diameter increases the stripping torque. Please consult our engineering department on your applications.

How, Why Where To Use Self-Clinching Fasteners

Broadly defined, a self-clinching fastener (also known as clinch or captive fastener) is any device, usually threaded, that, when pressed into ductile metal, displaces the host material around the mounting hole, causing it to cold flow into a specially designed annular recess in the shank or pilot of the fastener. A serrated clinching ring, knurl, ribs or hex head prevents the fastener from rotating in the host material once it has been properly inserted. Thus, self-clinching fasteners become a permanent part of the panel, chassis, bracket, or other item into which they are installed.

Generally, self-clinching fasteners take less space and require fewer assembly operations than caged or anchor nuts. They also have greater reusability and more holding power than sheet metal screws. They are used chiefly where good pullout and torque loads are required in sheet metal that is too thin to provide secure fastening by any other method. Even if the sheet is thick enough to sustain tapping, it may actually be more economical to use self-clinching fasteners with gaugeable threads. They can be installed during fabrication or during final assembly to eliminate loose hardware. In fact, the use of self-clinching fasteners often will support a thinner sheet metal, and permit a real reduction in installed cost over the cost of other fastener designs. Because of their compact design and low profile, they provide for a neat appearance, too.

As a rule, a self-clinching fastener should be specified whenever a component must be readily replaced and where “loose” nuts and hardware wouldn’t be accessible. If the attaching “nuts” and “screws” can’t be reached after a chassis or cabinet is assembled, self-clinching fasteners can be installed during metal fabrication and can simplify and expedite component mounting and assembly operations, including those performed in the field.

How do I use cage nuts?

You may have heard of cage nuts and wondered what they are and how they are used. Today we are going to discuss cage nuts and show you some of their advantages and uses.

Cage nuts are used to mount IT equipment in server racks, such as the StarTech.com 4POSTRACK25U. Server racks compatible with cage nuts can be easily identified by the square holes the cage nuts use. Cage nuts are great for protecting your equipment from stripped threads and allow for convenient mounting of your server rack equipment.

A cage nut houses a standard nut in a cage with a spring. The cage has two wings that can be pinched together to allow the cage nut to be inserted into a square hole. The wings are then released to hold the cage nut in place. Cage nuts come in many sizes but M5 and M6 cage nuts are mainly used in IT environments. M6 is a heavier, more robust cage nut that M5.

Let’s take a look at mounting a Cage Nut on a rail in the StarTech.com 4POSTRACK25U.

In some situations, you may be advised to use a slot screwdriver to help install cage nuts. However, you will find it much easier to use a cage nut mounting tool.

To install a cage nut, use your tool to attach one of the wings from the cage nut. Keep the pressure on the cage nut with your finger and then attach the other wing. The cage nut is now ready for the mounting screw.

To uninstall a cage nut, use your tool to release the cage nut wing on one side and then the other side.

You can check to see if your StarTech.com product includes cage nuts by navigating to the StarTech.com website, searching for the product, and checking the Technical Specifications tab under the heading What’s in the Box.

What are turned parts?

Turned parts are mechanically manufactured and mostly rotationally symmetrical parts that are produced by turning as a manufacturing process. Similarly, we speak of welded parts in welding, laser parts in laser cutting or milled parts in milling.

In the turning process, the workpiece is machined with the help of lathes for turning-milling centres. In this process, the turned parts are sculpted by a turning chisel. The excess material of the turned part is thus removed by the turning chisel, with often more than 1,000 rpm. The material specifications, the tools and the diameter to be machined influence the turning speed and the feed rate during turning.