There is a veritable host of threaded inserts to choose from when it comes to your manufacturing needs. Finding the insert right for a specific use, torque load, and conditions are imperative to delivering outstanding products that are durable and long-lasting.
Today, we’re featuring one particular insert type: The wire insert. The wire threaded insert was first used by the aircraft industry in the 1930s to accommodate the use of lighter and weaker aircraft materials to produce larger, heavier aircraft. Wire threaded inserts enabled the aircraft industry to use lighter materials without sacrificing durability.
Threaded inserts are fabricated in two main ways: in a solid configuration by machining solid metal bars, or by coiling wire in a tight fashion to act like threads. Coiled wire inserts are also known as helical inserts; wire inserts don’t have the same torque and pullout capacity as solid metal inserts, but they are a less expensive option that has many benefits, including durability and reliability.
A key difference-maker in favor of wire threaded inserts is that the load is distributed throughout all coils, rather than the first few threads absorbing the majority of the load as with solid metal inserts, which results in wear, tear and eventual failure.
Wire threaded inserts are lighter and smaller than solid threads and can also be introduced into a product design without prior accommodations. Wire or helical threads also enable the use of thinner parent materials without sacrificing quality. Wire inserts also reduce stripping, wear, and corrosion of tapped threads and better distribute residual stress loading into the coiled design. What’s more, wire inserts can operate in conditions where elevated heat levels are present.
Benefits of Using Wire Inserts
- Reduced cost
- Durable and reliable
- Easy incorporation into the existing design
- Enables the use of lighter parent materials without compromising strength
- Increased heat resistance
- Reduced wear, especially in products that require repeated assembly and disassembly
Variations of Helical Wire Inserts for Any Application
Helical wire inserts are available in many variations to meet the exact needs of an application. Inserts are available in two primary types: (1) Free-running wire inserts; and (2) screw locking wire inserts. Both types are offered in two installation styles: Tanged and tangless. All four variations are available in many materials and platings.
Free-Running Wire Inserts
Free-running wire inserts are made from austenitic stainless steel wire wound tightly into a helical coil that looks like a spring. Free-running wire inserts can be installed manually or via automated methods; they provide durability and are corrosion and heat resistant.
These wire inserts are larger in diameter than the tapped hole. When inserted, the insert gets compressed, creating solid surface contact and radial pressure that secures the insert in place.
Screw Locking Wire Inserts
Screw locking inserts — also known as prevailing torque inserts — offer the reliability of free-running inserts with the prevailing locking torque needed for applications that encounter cyclic vibration or impacts. This wire insert type deploys polygonal grip coils that apply radial pressure on the male thread. Each grip coil contains locking chords that penetrate the minor diameter of the free-running thread.
The locking flats get displaced as the male thread moves through the grip coils, resulting in the radial pressure (prevailing locking torque) upon the male thread. When the male thread is removed, the locking coils return to their initial form, enabling repeated assembly while maintaining good prevailing locking torque overall.
Tanged and Tangless Inserts
To install helical inserts, a hole needs to be tapped to match the size of the helical coil. Then, the coil needs to be screwed in using a helical insert tool. To achieve proper installation, the coil needs to be secured to rotate properly.
There are two ways to ensure proper installation: Tanged and tangless inserts. These inserts are identical in form, fit and function but different in the way they operate.
Tanged inserts extend the coil wire end across the entire radius of the insert, creating a grip point that enables a snug fit. After installation, the tang must be removed. A tangless helical insert deploys a drive notch within the coil that acts as the grip and therefore no tang removal is needed, reducing the installation process by one step.
Plating and Coatings
Wire inserts are used in a wide range of industries, many of which place helical inserts under stress and within potentially corrosive environments. This requires the use of platings and the applications of coatings to prevent galling and corrosion. Here are some popular plating and coatings:
- A versatile and popular coating is Dry Film Lubricant, which limits galling between the insert and the fastener. The Dry Film Lubricant is a Molybdenum Disulfide applied in accordance with AS5272 (Type 1).
- Cadmium plating is primarily used to protect against corrosion, but like Molybdenum Disulfide, it helps decrease the coefficient of friction between the insert and the bolt to minimize galling. Cadmium is applied in accordance with AMS-QQ-P-416.
- Silver plating is applied in accordance with customer requested AMS specifications. Commonly, AMS2410 is used for low to mid-range temperatures, or AMS2411 is used for high temperatures up to 1400°F.
- Electroless Nickel plating provides wear resistance and corrosion protection. Electroless Nickel is applied in accordance with AMS-C-26074, unless otherwise specified by the customer. Polished Silver is the standard finish.
There are numerous wire inserts plating, coatings and color codings designed to protect against corrosion and to identify different wire inserts.
Tanged and tangless wire inserts can be ordered in bulk and a variety of packaging options. Bulk orders can come in packages with 1,000 wire inserts and larger helical inserts (above ½ inch) can be ordered in smaller quantities. Inserts can also be purchased on plastic strip-feed reels as well, with up to 1,000 wire inserts per reel.
We hope this quick overview of wire/helical threaded inserts will be useful as you search for the best and most efficient threaded inserts to maximize product performance. HTF’s catalog offers a wide array of helical inserts, platings, coatings and colors for any application.
We have been a trusted distributor partner to countless companies, and we are always poised to help you in any way we can. We have a wide array of wire coil threaded inserts and other threaded inserts for plastics available that can meet any need and function. And we can deliver it faster than our competition.
HTF has a track record of more than 30 years of delivering the components our clients need when they need them. We take great pride in having what you need and getting it to you when you need it while delivering the highest level of customer service in the industry. That’s why the top manufacturers in the industry partner with us.
Reach out to us today. We’re ready to help.