Threaded Inserts

There are various things that you have to consider when installing threaded inserts. This may include the material where the inserts will be used, the intention for using the inserts and the equipment necessary for the installation of the inserts.

Application Material

The material where the inserts will be installed – thermoplastic, thermoset or DMC – will influence the achievable performance as well as the installation method.

Types of Performance

Torque – this is the maximum rotating force being applied to the insert before spinning it in the molding.

Pull-out – this performance is considered as the maximum force often applied in a direct line, which often results to the failure of installing the insert to the host material.

Jack-Out – this is also a maximum rotating force that is applied to the insert before it is pulled out.

Methods of Installation

There are two different methods that can be used when installing threaded inserts. First is the post-molded installation. This method include three other methods known as ultrasonic or heat, cold and screw in and each of these methods have its advantages and disadvantages. Another method of installation is the molded-in installation. This method provides maximum performance, but may require the inserts to be directly installed to the mould tool which can be a disadvantage.

Choosing the Appropriate Brand of Threaded Inserts

There are various types of inserts in the market that will suit various applications, performance and materials. There are inserts available for ultrasonic or heat insertion and inserts for hot and cold installation into thermoplastic materials. There are also inserts available for screw-in installation and cold installation for both thermoset and thermoplastic materials, as well as inserts for molded-in installation into rotational moldings and thermoplastic and thermoset materials.

The Right Installation Equipment

There are different equipment necessary for insert installation. A heat installation machine offers consistent and solid insert installation by maintaining a temperature between 500 and ambient. This type of machine is cost effective and can provide high performance when installing male or female inserts. A screw-in installation machine is maneuverable and highly flexible. Its assembly is expandable as well, thus allowing you to incorporate three arms in a single column and this provides faster performance when installing multi-sized inserts into a single molding, as each arm can be dedicated to an insert of certain size. An arbor press, on the other hand, can be used for the cold installation of inserts. The pinion operation and the simple rack of this machine require low maintenance and deliver a reliable and solid installation of the inserts.

Dealing with the Common Installation Problems

When installing threaded inserts, it is natural to encounter various problems, especially if you are not used to doing it or this is the first time you are trying to install inserts. Some of the most common problems that you may encounter have something to do with the pullout, the jack out and the boss cracking. If you are not familiar with how you can troubleshoot or deal with these problems, you can simply do a little research over the internet or seek the help of a professional insert installer for better understanding or better yet, have the installation done by a professional to prevent any problems.

Most pipes and rods, whether made of plastic or metal, can be machined to give them threads. These threads can either be external in the case of solid rods and either internal or external for pipes. Most of the time, these threads get damaged and need to be repaired. It’s simple enough to repair external threads. There are a lot of thread repair machines to do the job. One can even do it by hand. And it’s easy, if you know what you’re doing.

Internal threads, however, are much more complicated to install, and that much harder to repair. And in times past, it’s virtually impossible to do this without a machining operation. Fortunately, the arrival of threaded inserts eliminated the need for big, bulky and dangerous machines to repair damaged internal threads. These inserts are so versatile that they can even put a thread where before it is impossible to do so. And the resulting product is durable enough that a yearly installation of replacement inserts isn’t necessary.

There are several types of threaded inserts and each is designed for a different job. Here we take a look at some of them and what they do. One of the most commonly used is the captive nut, otherwise known as insert nut. They are used in pipes that are too thin to be threaded. They are internally threaded and they are set into the pipe by arbor presses. The captive nut fastens to the pipe with its knobbed edges and its internal thread is now ready to use. Press fit inserts are similar to captive nuts, having a knobbed outer edge for locking in. The only difference is these inserts are installed in holes with thicker walls.

Externally threaded inserts have as many brands as they have methods of installation. Whatever the brand, these inserts all have internal and external threads, and they are locked into place by different methods. Some tap their own threads while others are inserted into pre-threaded holes. EZ Loc is the brand name for an insert that is anchored in place by Loctite. Others are locked into their holes by keys that are hammered into them. Self-tapping inserts or self-threading inserts lock into place using friction; it’s difficult to install the insert and the friction of reversing the process will lock the insert into the hole.

A helical insert is made of coiled wire. It looks very much like a very rigid Slinky or a spring coil with no spaces between the coils. This insert is more commonly known by its brand name Heli-coil. It needs no machining to be installed but the worker must use special tools. Its outer diameter is larger than the diameter of the hole that it is supposed to be attached to, but not large enough that it’s impossible to install. Being larger than the hole, it’s extremely difficult to remove once it’s installed.

A mold-in insert has internal threads. It is different from the other inserts in that the shape of its outer diameter is dependent on the shape of the pre-molded part that it is supposed to be inserted into. It is locked into place by filling the space around the insert with molten material, either plastic or metal, and letting the material dry out.

Whatever the type of damaged internal thread, there is a threaded insert capable of repairing it. You just have to pick the right one that will do the job and do it right.

Threaded inserts are fastener-related devices constructed of metal or plastic materials. They are generally used to provide thread tracks for screws or bolts. These inserts can allow a fastener to form a more secure attachment to soft or pliable surfaces that would otherwise reject fastening, repair a damaged thread track, or install threads into a workpiece without relying on a more elaborate production process. Threaded inserts are usually placed inside an existing hole or slot, and they feature an external design that allows them to be lodged securely, along with a cylindrical inner cavity lined with threads.

Fastener inserts can be made from a wide range of materials, including metals such as brass and steel, and plastics such as PVC. Likewise, they are available in a variety of design types depending on their application. Molded inserts are used in plastic fabrication cavities, while key-lock inserts are employed for repairing stripped thread holes. Threaded brass inserts are most often used for fastening plastic materials, although they can also be applied to wood and other surfaces as well. Installing these inserts is usually a multistage process, and can sometimes require special equipment or techniques to accomplish.

Threaded Inserts in Wood

Installing a threaded brass insert into a wood surface requires a certain degree of care. A threaded rod with a length depending on the specific application needs will be required, along with a few similarly-sized nuts, masking tape, and copper tubing with an internal diameter slightly larger than the external diameter of the threaded rod.

First, a pilot hole must be drilled into the wood at the point where the threaded insert will be installed. To help keep the angle of insertion perpendicular to the surface, it can be helpful to mount the workpiece in a drill press, but it is important that the drill press is off during the procedure. The workpiece should not be clamped too tightly because the threaded rod should be able to rotate inside the copper sleeve. The rod can then be twisted into its slot with a wrench, while masking tape is used to keep it from slipping out of the copper tubing, which functions as a sleeve. Depending on the hardness of the wood, considerations may need to be taken for clearing chips from the area.

Threaded Inserts in Thermoplastic

Putting threaded brass inserts in a thermoplastic material, such as acrylic, involves a different set of equipment and methods than those used for wood surfaces. In some cases, the insert may need to be melted into the workpiece in order to form a secure joint. Generally, this occurs on the more rounded side of an acrylic piece as a smaller amount of melted plastic will gather near the insert and the installation will be easier. The standards steps in such a procedure include:

o Positioning: A threaded brass insert usually has a taper on one side to help with insertion into a slot. Inserts should be placed along the surface of the thermoplastic workpiece in their intended spots, ideally along a series of predrilled holes.

o Insertion: The workpiece should be clamped or moved to ensure that the insert holes are overhanging the edge of a bench or other work surface, and a heated soldering iron may then be pressed into the threaded insert. Applying a slight amount of pressure onto the soldering iron will help push the insert straight down into the material.

o Protrusion: The soldering iron can be used to guide the insert and keep it straight as it enters the workpiece. The insert should be pushed until it lies flush with the top surface of the workpiece, although there may be a small accumulation of melted plastic that rises over the insert. Depending on the application requirements, the insert should also be checked to see if it lies flush with the bottom half of the plastic surface.

o Inspection: After the threaded insert has been installed, it may be helpful to use a screw or bolt to verify its positioning. If the screw attaches at a bent angle, the soldering iron can be applied to reposition it correctly.

It may be necessary to preheat an insert on the soldering iron before beginning installation, especially if working with a large brass insert. Alternatively, a drill press can be employed to grip the workpiece while heat is applied to the insert, although the press should not be turned on during the process.

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