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Stainless Steel vs. Brass Threaded Inserts for Plastic

March 7, 2022Generated with Avocode.Ellipse 1By E-Z Lok

When it comes to using threaded inserts in the construction of plastic materials, both the plastic and the insert material matter based on the application. Assemblies made from plastic and other soft materials often rely on metal threaded inserts to reinforce joints and secure fasteners. But which type of metal inserts can be considered superior? Today's two most common options available on the market are brass and stainless steel threaded inserts.

Brass threaded inserts are generally regarded as the better option. However, with increasing thought being put into sustainable options, lead-free alternatives such as stainless steel are growing more popular. In this article, we'll break down the "stainless steel vs. brass threaded inserts" argument and highlight some of the benefits and best uses of each so you can make an informed decision based on your project. Keep reading to learn more.

The Benefit of Brass Threaded Inserts

Brass threaded inserts for plastic and 3D printing thermoplastic applications are typically slotted to minimize splitting or splintering. As mentioned, when comparing stainless steel vs. brass threaded inserts, most manufacturers agree that brass is the better option for a wide variety of reasons. That being said, let's get into some of the benefits that come from using brass inserts over stainless steel.

First, brass threaded inserts offer greater thermal conductivity than threaded inserts made from austenitic stainless steel. In fact, brass inserts are typically 15 times as conductive as stainless steel inserts, meaning brass is optimal for heat and ultrasonic installation methods. Good thermal conductivity also translates to an installer having better positional accuracy when setting brass threaded inserts for their project. Brass also cools quickly. Installers can have better peace of mind knowing that brass threaded inserts can be set promptly and accurately in components without the inserts moving within the plastic hole and compromising the entire project. Compare this with stainless steel inserts, where installers must brace the steel insert within the molten plastic after it is put into position, so it doesn't "float" around in the hole, compromising the joint integrity of the finished assembly.

When comparing brass and stainless steel, it's also worth noting that brass threaded inserts are much more valuable than stainless steel inserts. As a result, manufacturers can recover more material costs after manufacturing if they choose brass inserts. Brass threaded inserts also possess great strength, allowing solid and durable holds. When an installer wishes to make a threaded part stronger, they only need to increase the thread length of the brass threaded inserts to avoid the higher cost of stainless steel.

Other benefits of brass threaded inserts include resistance to exposure from mild alkaline solutions and corrosion in non-oxidizing acids and petroleum products. However, installers should avoid strong alkaline solutions such as hydroxides, cyanides and oxidizing acids.

The Benefit of Stainless Steel Threaded Inserts

Although stainless steel inserts are appropriate for use in some projects, it's often somewhat unnecessary. When deciding to use stainless steel or brass threaded inserts, brass usually satisfies most requirements at a better price. That being said, stainless steel threaded inserts carry benefits of their own which may be more useful to installers.

Stainless steel threaded inserts are available in more varieties than brass inserts, though 300 series and austenitic stainless steel are the most common forms an installer will find on the market. When thinking of stainless steel vs. brass, the properties of stainless steel inserts vary dramatically from one alloy to the next, making it more challenging to generalize their benefits. However, stainless steel threaded inserts offer excellent resistance to petroleum products and most acids. Though installers should avoid hydrochloric acids, stainless steel inserts can easily be passivated in either citric or nitric acid solutions.

Stainless steel inserts can also provide higher strength than brass threaded inserts depending on the grade/alloy used, giving projects a more durable hold and better resistance to vibrations.

Applications of Brass & Stainless Steel Threaded Inserts

Most installers accept that brass inserts offer more significant advantages when deciding to use brass or stainless steel inserts. For example, brass threaded inserts are the preferred standard for most industrial and agricultural applications due to their specific qualities. Still, there are plenty of instances where stainless steel threaded inserts are preferred. Let's explore the applications of stainless steel vs. brass threaded inserts.

Brass Inserts

Brass threaded inserts are excellent for both hot and cold-water industrial systems and similar residential systems. This includes systems that carry potable water for consumption. Brass inserts are also quite suitable for some types of marine environments, including brackish water and seawater with low to moderate currents. Once an installer exposes a brass threaded insert to a marine atmosphere, it will develop a layer of protective green patina.

Brass threaded inserts also typically perform well in cryogenic applications, making them a suitable alternative to 300 series stainless steel threaded inserts in certain environments.

Brass threaded inserts can also be nickel-plated to reduce any tarnishing or corrosion. Nickel-plated brass inserts are generally used on gears, bearings and plumbing fixtures.

Stainless Steel Inserts

Certain grades of stainless steel threaded inserts, such as the 316 series, are far superior to brass inserts in aggressive marine environments with fast-moving currents. However, this does not apply to all grades. The most common grade of stainless steel inserts, the free-machining 303 series, contains added sulfur that can improve machinability. However, sulfur additives decrease corrosion resistance in seawater.

Certain grades of austenitic stainless steel threaded inserts, such as 302, 304 and 316 series are FDA approved for food contact. This makes stainless steel inserts the best choice for food and beverage applications.

Note: Free-machining 303 stainless steel inserts are not approved for use in contact with foods.

Shop E-Z LOK for Steel or Brass Threaded Inserts to Finish Your Project

Though brass inserts are an excellent choice for most plastic and thermoplastic applications, there are certain instances where stainless steel inserts are preferred. When deciding whether you want to use steel or brass threaded inserts, it's essential to fully understand that all materials carry unique characteristics. Once you know whether or not you want to use brass or stainless steel for your specific application, head on over to E-Z LOK for top-rated threaded inserts of all kinds. Whether you need threaded inserts for your plastic, wood or metal projects, E-Z LOK has you covered with strong threads ready to take on the job.

If you have any questions about our brass and stainless steel threaded inserts, contact us right away to speak to a member of our team or browse our threaded inserts knowledge center. We're always happy to help.

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