Key Questions to Ask When Ordering custom metal threaded inserts

That’s why we thought this would be a great time to write the first in what will probably be a series of articles about inserts.

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(A series of articles about inserts? Hey, we love what we do!)

Four Key Questions for Choosing an Insert

If you’re serious about finding the right insert for your needs, the best way to start is to not think about inserts.

That sounds like a contradiction, but it’s true. Here at Olander, we carry hundreds of different kinds of inserts. Your first instinct may be to start scrolling through your options, reading up on features, and comparing prices.

Please don’t. Instead, start by asking yourself the most important question about inserts: “What am I going into?” Your choice of insert must be dictated first and foremost by the kind of material you’re working with.

Your second question should be: “Am I drilling a new hole or filling an existing one?” Some inserts are most appropriate for new builds, while others work better for repairs.

Your third question should be: “Do I have the right tools for the job?” Many inserts require you to drill a specific size hole, use a special tap and the proper installation tooling. If you don’t have the tool handy, the insert won’t achieve the desired result.

And your fourth question should be: “What will be the usage pattern for this hole?” A hole in which the bolt will be removed frequently could need a material and insert design that is different than a hole where you’re installing once and forgetting about it.

We’re always happy to walk customers through these questions when they call us. But you can get a head start by thinking about these issues in advance.

Some Inserts We’d Like You to Meet

Let’s get down to inserts. In answer to the first question above, you may be drilling into sheet metal. If so, we generally recommend a Thinwall Blind threaded insert.

For example, AVK inserts are ideal for when the material you’re fastening to is too thin for thread tapping. Once you’ve made that determination, you can start figuring out the best thread size for your situation and what material your AVK insert should be made out of.

What if you’re going into thicker material, such as a metal plate? If you’re designing a new product and plan on using inserts in many holes, a Heli-Coil insert could be an excellent choice for you.

Heli-Coil inserts are wire inserts that are available in various lengths and materials for a wide range of applications. With Heli-Coil, you will incur a tooling cost up front to tap threads for a custom hole. But once you’ve done that, you’ll find the Heli-Coil Wire Thread to be a cost-effective and durable insert.

Now, what if you’re going into weaker material such as aluminum and want to install a durable insert that will withstand frequent removal of the bolt? Along with a Heli-Coil inserts, key locking insert (also known as Keensert or keysert) may be the way to go.

Key locking inserts are threaded inserts that are great for reinforced threads in softer parent material. They’re also a good solution for replacing damaged or stripped threads in an existing hole.

Now, key locking inserts are larger inserts, so they require more material around them (they’re not good for applications in very tight spaces). Once you’ve threaded a key locking insert into a machine-tapped hole, you’ll drive down the keys to lock the insert into place.

You’ll find that key locking inserts are more expensive per part than Heli-Coil inserts. But since you only need inexpensive tooling to install them, you’ll save money up front. By contrast, a Heli-Coil manual tooling insert may cost you $150-200 for installation, but after that, each part will cost pennies instead of dollars. Your cost analysis, then, will always revolve around how many inserts you need for your project.

Where to Go From Here?

We’ve given you a lot of information about inserts….and we hope your head isn’t now spinning as quickly as your drill bit.

Believe it or not, this article only scratches the surface of the amazing options that are available to you when you go shopping for inserts. Need a hand selecting the right inserts for your next project? Drop us a line at Olander. We’re here to help you Hold It Together! And look for our next article soon.

What is the difference between a coil thread insert and a Heli-Coil? Actually, there is no difference. Just as Kleenex is commonly used to refer to facial tissue and Xerox has become synonymous with photocopies, “helicoil” has become a commonly recognized term for screw thread inserts. Heli-Coil® is a registered trademark of Stanley Engineered Fastening, a division of Stanley Black & Decker. Its design has become the industry standard for coil thread inserts.

Coil thread inserts, also known as helically wound inserts, are coiled wire inserts placed inside the drill hole to create a strong threaded surface to secure a bolt or other threaded fastener. When a drill hole has been stripped or the material is too soft to secure a drilled fastener, as can be the case with magnesium, wood, aluminum, zinc, or plastics, the coil provides an extremely strong and lasting bond by transferring the pressure exerted from the bolt to the sides of the parent material.

The helically wired coil is screwed into place and creates a threaded track for the screw threads of a bolt or fastener. The diameter of the coil is wider than the tapped hole, so as the bolt is screwed in, the coil compresses against the side of the tapped hole. This compression creates a safe and highly secure connection—much stronger and with more torque than similar assemblies. In fact, when used for repairs, coil thread inserts create a stronger bond than the original tapped hole.

With ordinary bolt-and-hole inserts, the top two screw threads carry 65-75 percent of the load. Helically wound inserts distribute the load so each coil shares part of the load across the length of the coil. The result is a stronger connection and longer thread life, even after assembling and disassembling multiple times.

Coil thread inserts are especially useful in applications that have to withstand stress, severe vibrations, and extreme temperatures. Even under extreme conditions, these inserts minimize wear of the threaded hole and increase the integrity and useful lifespan of the connection. That’s why coil thread inserts have become a popular fastener solution for critical applications such as automotive manufacturing, aerospace, railways, factory machinery, and transportation systems.

Coil thread inserts are quite versatile and available in a wide range of thread diameters and thread sizes. They also come in a variety of materials. Stainless steel coil thread inserts, for example, are resistant to corrosion and extend the useful life of the fastener. They also can withstand temperatures ranging from -320 degrees to +800 degrees Fahrenheit because the coils can expand and contract with temperature changes.

Link to Prototype Finder

Tanged Coil Thread Inserts

Tanged coil thread inserts have a straightened piece of coil at one end that extends across the radius of the coil. This piece is called a “tang” and is used as an anchor during installation. A special helical insert tool grips the tang and uses it to screw the coil into the tap hole. Once the coil is inserted and secured, the tang is broken off and removed.

CoilThread tanged inserts are extremely reliable and long-lasting. CoilThread is made from cold-rolled 304 stainless steel wire (AS), and work-hardened to a rating of Rc 43-50 and a tensile strength that exceeds 200,000 psi. More importantly, the finished surface is extremely smooth (8-16 microinches), which virtually eliminates thread erosion caused by friction. CoilThread is also available in other materials, such as phosphor bronze, Inconel X-750, Nitronic 60®, Nimonic 90®, and titanium, as well as stainless steel. They also come with special coatings for specific applications.

Tanged coil thread inserts fall into two basic subcategories:

• Tanged free-running coils are designed so each coil adjusts independently, which means each bolt or fastener thread adjusts itself for maximum efficiency. More surface contact between the individual threads and the parent materials makes for a stronger bond because the load is distributed evenly across the entire coil. Free-running coil thread inserts also are subject to less stress because there aren’t specific stress points, which means no fatigue concentrations and fewer failures. Stainless steel free-running coil thread inserts resist corrosion and reduce galvanization, eliminating corrosion caused by a chemical interaction between the bolt or parent material and the coil.

• Tanged screw-lock coil thread inserts also use a tang for coil insertion, but they additionally feature a series of straight segments as part of the coil. Once they are inserted in the tapped hole, the entry of the bolt flexes the straight segments outward for a stronger bond. This places more pressure on both the bolt threads and the parent material, maximizing the contact area. Locking inserts are designed to meet the rigorous specifications of the NASM aerospace standard for military applications, which requires the inserts to pass a 15-cycle torque test.

Both free-running and screw-lock tanged helical inserts come in UNF sizes (measured in inches) and metric versions.

Tang-free Coil Thread Inserts

Tang-free coil thread inserts, as the name implies, do not have a tang at the bottom of the coil. Instead, there is a driving notch strategically located in the coil that serves as a grip point for the helical coil insert tool. Tang-free coils are identical to tanged coil thread inserts, other than lacking a tang, and are available in free-running and screw-lock configurations.

Increasingly, manufacturers are moving to tang-free coil thread inserts because they are just as easy to install and they eliminate the need to remove the tang. This removes the risk of loose tangs or pieces of metal getting into the machinery, and it speeds up installation and inspection time. Some helical coil makers estimate you can save between $0.15-$0.50 per hole by standardizing on tang-free coil thread inserts. These helically wound inserts are especially popular with electronics manufacturers and high-tech manufacturing—wherever smaller, high-precision inserts are used.

Tang-free coil thread inserts are available with the same free-running and screw-lock designs as tanged coil thread inserts, with all of the same advantages. They are made out of work-hardened steel and other materials for maximum strength with minimum friction. They also are available with custom coatings. All tang-free coil thread inserts are available in UNF (inches) and metric sizes.

Additionally, all coil thread inserts come in either bulk or strip-fed versions, where the inserts are positioned in a plastic ribbon which is passed through an assembly nozzle. Strip-fed coil thread inserts are used in high-volume production applications with tooling that accepts strip-feed inserts. All types can be inserted by hand or using a strip feed. With tangless coil thread inserts, ribbon-fed inserts can increase the number of installation cycles with less operator fatigue.

Kato Fastening Systems

Kato Fastening Systems has made coil thread inserts since the s. Kato coil inserts are widely used in the aerospace industry and their ColiThread inserts are made of cold-rolled stainless steel with a tensile strength of 200,000 psi.

Kato inserts also are available in a variety of materials for different applications:

• Inconel X-750 is a nickel-chromium alloy hardened by adding aluminum and titanium for high-temperature applications up to 1,000 degrees Fahrenheit (ideal for nuclear reactors).
• Phosphor bronze inserts are ideal for saltwater applications because they resist corrosion. They have a tensile strength of 140,000 psi and a hardness of HRB 95 with low magnetic and electrical conductivity, making them ideal for naval vessels, aircraft instrumentation, mining and drilling, and similar applications.
• Nitronic 60® is designed to minimize friction and galling with stainless steel screws thanks to the addition of silicon and manganese to the alloy. No additional coatings are required, so they are useful in a vacuum because there is no outgassing. They are non-magnetic and corrosion-resistant, and are typically used in aerospace and semiconductor manufacturing.
• Nimonic 90® inserts are designed for extreme pressure and extreme heat. This is a nickel-chromium-cobalt alloy that is useful for jet engine parts, exhaust nozzles, and turbine components, among other applications.
• Titanium coil inserts offer a superior strength-to-weight ratio. They have a slightly lower tensile strength than steel coils but are much lighter, so they are typically used in biomedical applications such as implants and prosthetics.

Recoil from Arconic Fastening Systems

Arconic’s line of Recoil coil thread inserts are manufactured in Australia, although the company also has warehouses in North America, Asia, and Europe. Recoil fasteners are available tanged and tang-free in a wide range of metric and standard sizes and in free-running and screw-lock configurations.

Recoil coil inserts also come in a variety of materials, including stainless steel (grades 304 and 316), Inconel X-750, phosphor bronze, Nimonic 90, and Nitronic 60. This versatility makes Recoil inserts useful for various applications and industries, such as automotive, ship building, power generation, manufacturing equipment, consumer electronics, aerospace, transportation, and industrial electronics, to name a few.

A variety of lubricants and coatings also are available:

• Silver plating reduces galling of screw threads in high-temperature applications, such as aerospace engines in which service temperature can reach 1,200 degrees Fahrenheit.
• Cadmium plating is useful as an anti-corrosive for marine applications, providing protection against pitting and thread seizure.
• Dry film lubricants are used in mildly corrosive and high-temperature applications. Dry film lubricants have small particles of solid lubricants applied as a thin film to grease-free metals. Film lubricants can be formulated for various industrial applications.  
• Tin plating is specified in ISO for moderately corrosive applications, such as auto manufacturing,
• Red dye or other color coatings can be applied for identification purposes.

In addition to helically wound inserts for manufacturing, Recoil also offers thread repair kits, complete with an STI (screw thread insert) tap, installation tool, tang removal tool, drill, stainless steel inserts, and instructions.

Here is an overview of some of the additional requirements you should understand when installing coil thread inserts:

Coil Thread Insert Tools – Helically wound coils can be inserted by hand or using any number of power tools. Coil thread insert tools are available in pneumatic, hydraulic, and electric-powered units from manufacturers such as Atlas Tools, Advel, Gesipa, and Recoil. Kato and Advel also offer manual tools, which are ideal for simple repair jobs.

• Pneumatic tools typically are used for high-volume, industrial applications, such as in a factory, using strip-feed coil thread inserts.
• Electrical coil thread insert tools are becoming increasingly popular. For heavy-duty, high-volume applications, electrical tools can perform at high speeds.
• There are also battery-powered versions available for handheld installations, as in automobile or aircraft repair. Some of the more advanced electrical and pneumatic tools also have built-in prewinders, which compress the coil thread insert before it is inserted into the tapped hole.
• Manual tools are available for occasional uses, such as repairs.

Coil Thread Inserts Insert Lengths and Drill Sizes – In order to gain the full load value of the bolt, you have to choose the helically wound insert that is the right length for the job. A coil thread insert size calculator has been developed using the ASME B18.29.1– standard and the HASM standard to determine the right insert size for maximum efficiency.

Coil Thread Insert Sizes – In addition to coil length, you need to be sure you have the right coil thread insert width for the job. Determine whether you need tanged or tang-free inserts, the size of your tap holes, and the insert material that’s best for the job.

Coil Thread Insert Kits – For smaller applications and repair jobs, you may need a self-contained insert kit, which includes manual insert tools and a variety of inserts.

Once the hole is drilled, you need to tap the hole using an STI to create a screw thread. You can then use an STI Go or No Go gauge to ensure the pitch is correct through the entire tap hole.

The standard type of STI tap creates threads that match the coils of the insert. These taps are usually used on a CNC machine or high-precision equipment to ensure that the fit is exact. When preparing a hold for a screw thread insert, a drill bit is used first to open the hole to the correct minor diameter. The STI can then be inserted to create the proper threads to receive the insert.

There are different types of taps with various designs, including two-thread chamfers and four-thread chamfers, which are useful for drilling blind holes, and fluted taps, which remove chips of material as they turn.

Now you can install the insert itself. The coil thread insert is fitted on the end of the tool and screwed into the hole. If you are using tanged coil inserts, the tang will fit in a notch at the end of the bit to provide a secure grip to rotate the coil. With a tang-free coil, the bit should grip the notch in the coil. Once the insert is secured, another tool is used to grip and break the tang; to prevent having loose metal, it is important the tang be removed and not just broken off.

Now the coil is ready to accept the bolt or fastener. As the bolt is screwed into the tap hole, the coils or locking coils will flex outward, generating pressure on the bolt and the parent material for a secure seal. The spring-like design of the coil transfers the shear load into radial load across the entire length of the insert, which virtually eliminates failures caused by high stress.

What are coil thread inserts used for?

Coil thread inserts are used to create especially strong connections for bolts or screws by reinforcing the tap hole. Helically wound inserts are used in manufacturing because they create more durable fastenings that are resistant to vibration and extreme temperatures. They also are used to repair stripped screw threads in drill holes.

What is a screw thread insert?

A screw thread insert is an insert of coiled wire that is screwed into a tap hole to accept a bolt or threaded fastener. The insert is typically larger than the hole, so when the bolt or fastener is screwed in, pressure on the coils of the insert creates a stronger bond between the screw threads and the threads of the hole in the parent material.

What is a free-running coil thread insert?

A free-running coil thread insert consists of wound wire designed to fit into the threads of the tap hole so each coil has a unique fit. As the bolt or fastener is screwed into the hole, the coils act independently to form a more secure bond between the bolt and the parent material. Using a free-running coil thread insert also extends the load from the first few threads of the tap hole to the entire length of the coil.

What is a screw-locking insert?

A screw-locking insert is a coiled insert with one or more flat coils. When a bolt is inserted, the flat coils flex outward, placing additional pressure on both the bolt threads and the threads in the parent material to form a stronger, more stable connection.

What are the benefits of using a tang-free coil thread insert?

Tang-free coil thread inserts use a notch in the coil itself rather than a tang extension for installation. This means fewer steps during installation because there is no tang to remove and less risk of loose metal interfering with other parts or machinery.

What are coil thread inserts made of?

Coil thread inserts are made of a wide range of materials, including work-hardened steel, bronze, and titanium. The coil material should match the application. For example, steel coil thread inserts are most common because they are extremely durable; bronze inserts are less likely to corrode in saltwater; and titanium inserts are lightweight.

What is a time-sert?

A time-sert is a solid bushing insert that is typically used to repair stripped threads. Unlike a coil thread insert, a time-sert is solid with threads already molted into the sleeve, and it has a flange at the top to ensure the time-sert doesn’t wind down into the repaired hole.

For more custom metal threaded inserts(fr,ms,pt)information, please contact us. We will provide professional answers.