Choosing the Best Materials For Your Gears

When choosing the best alloy steel for gears, there’s a lot to consider. Heavy-duty applications are no place for guesswork, which means understanding exactly what you need from your gears and what materials will best serve you.

This is true whether you work in aerospace, robotics, packaging and labeling, medical, 3D printing, automotive, machining, agriculture, or any other industry. Simply put, until you understand the possible options and their specifications, you’re at a disadvantage in your field. Moreover, using the wrong materials can lead to:

Compliance and regulatory issues that may lead to lawsuits or shutdowns
Dangerous situations for your workers, your machines, and your business
Poor performance of gears, pulleys, and tools that lead to reduced overall functioning in your shop or warehouse
Loss of clients or even your good name

Obviously, these are outcomes best avoided. And by selecting the right ingredients for fabrication, you can do just that. Let’s take a look at the types of gear materials available as well as which ones fit which applications.

Types of Gear Materials

The system in which a gear will function dictates what that gear must be able to handle. This includes considerations such as:

How great a load will the gear need to bear?
For how long at a time will the gear need to do its job before it gets rest? (This is important when it comes to heat resistance, for instance.)
What type of environment will the gear operate in? Will there be magnetic fields, heat, or corrosive elements against which it must be protected?
What is your budget?
What is your industry?
What types of gears have you had before, and have they worked for you?

The answers to these questions will dictate which material is the best alloy steel for gears. In some cases, alloys aren’t even the answer and you’ll turn to more esoteric options, such as thermoplastics, which we will discuss in more detail below.

Alternatively, the material of the gear can literally shape it, determining its geometry for the specific application. If you know what material you want to use, the design process will then revolve around its needed capabilities. Again, this will account for the application, the presence of corrosives or magnetics, operating time, environment, and so forth.

Either way, the most common alloys fall into five basic categories: copper, iron, tool steel, aluminum, and thermoplastics. Below, you will learn more about what each of these alloys contains, the functions they perform best, the types of environments for which they are suitable, and more.

By the time you’re done reading, you should have a good idea what type of material will work for your gears. If you want to skip to the good part, feel free to scroll to the bottom and give us a call today!

In the meantime, read on.

Copper Alloys

Copper is an excellent material for environments that tend to corrode gears, such as applications that involve water or other elements. In fact, copper has been used in piping for thousands of years, dating as far back as Ancient Egypt.

It is also a great material for environments where the gear must be non-magnetic, continuing to function even under magnetic and electromagnetic conditions. Copper does not respond strongly to magnetic fields, which is why it makes such a good insulator. In fact, unless it is in the presence of a very large magnet, you’d never be able to tell that it wasn’t inert.

Although it is not technically an inert metal, because its electrons do react with other elements, it is a very good runner-up when you’re looking for a material that won’t quickly corrode, oxidize or wear away.

Over time, it does turn green, but it takes years for this patina to develop. Combining it with other elements can reduce this tendency quite a bit further, meaning gears that use copper have life spans measured in years or decades.

Copper typically comes in one of three alloys:

Brass: This alloy marries copper and zinc in different amounts depending on how ductile you need the alloy to be. Less zinc, and the alloy remains more flexible; more zinc and it is less ductile. Copper makes it easy to work and antimicrobial. This alloy is ideal for low-load environments.
Phosphor bronze: This copper alloy swaps out zinc for tin and phosphorus. Together, the three metals become strong, anticorrosive, and wear-resistant.
Aluminum bronze: The name of this alloy is a bit misleading, as it is actually a combination of copper, iron, nickel, manganese, and aluminum. These are even less likely to wear and corrode than phosphor bronze.

Iron Alloys

Iron has made a name for itself when it comes to strength and durability since the Iron Age began around 1,200 BCE. The ability to work steel forever altered humanity’s options, and since then, we have enjoyed a superior addition to the selection of alloys.

Cast iron is the most basic form of this element, poured in its raw form into molds that determine its lines and angles. It is a cost-effective alternative to phosphor bronze in applications where magnetic fields don’t come into play. (Iron is not suitable when they are a factor, as it responds strongly to magnets.)

Steel, an iron alloy, melds iron with carbon and other trace elements, depending on the specific type of steel and application. Steel is easy to machine, very strong, with both ductility and hardness on its side. It is also quite resistant to wear.

If you’ve ever seen steel labeled with four numbers, look at the second two. These tell you the fraction of carbon used in the alloy. Different ratios are ideal for different situations, but if you’re not sure what you’re looking for in a gear, speak to an expert. They will be able to guide you toward the correct alloy.

Stainless steel, carbon steel, and alloy steel are all names you might have seen in reference to iron alloys, as well as tool steel, to which we turn our attention next.

Tool Steel Alloys

In addition to being the best alloy steel for making gears, tool steel alloys are used in a wide variety of applications. These are made with trace elements such as tungsten, vanadium, molybdenum, and cobalt, all of which increase its durability and resistance to heat.

The reason this is the best alloy steel for gears is because of its hardness and resistance to wear. Tool steel is named for its use in tool parts, because its chemical makeup lends it extreme toughness – think drill bits, punches, saw blades, and other grinding or cutting surfaces.

Tool steels are made in different ways to respond to the different environments in which they must operate. For instance:

Water-hardened steels have been quenched in water after machining, giving them an extremely hard and durable outer layer. However, this makes them more brittle, so they are not suited to all applications.
Hot-work tool steel can take higher temperatures for work that is literally hot. This includes high-temperature manufacturing with malleable materials, e.g. glass or metal.
Cold-work tool steel, as the name suggests, is for cold work. They offer major compressive strength, which is necessary to cut elements at temperatures below freezing.
High-speed tool steel alloys are made to stand up to the rapid pace of manufacturing. Even at very high rates of operation, which in turn create high heats and considerable stress on the parts, high-speed tool steels hold up.

For this reason, tool steel alloys are the best choice for gears. Gears must turn quickly, tirelessly, for many applications. Depending on the heat, cold and other factors at play, you can choose specific ratios of iron, carbon and other elements.

Aluminum Alloys

When you need to throw off some weight but don’t want to sacrifice toughness, aluminum alloys can be a good substitution for steel. They are less than half the weight of steel alloys, going by size, with a finished surface that protects the alloy from corrosion and oxidation.

While aluminum costs more than carbon steel, it is cheaper than stainless steel. The relative ease with which you can machine aluminum alloys, however, helps to defray the additional cost as compared to its carbon cousins.

Note that aluminum is not appropriate for high-heat applications, however. It does not tolerate temperatures above 400°F, at which it will begin to warp.

Thermoplastics

Last but certainly not least, we have the thermoplastics family. The overriding benefit of thermoplastics is how tolerant they are of heating and cooling. While they soften a bit when heated, they harden right back into place when cooled, without changes in chemical structure. This makes them self-lubricating.

Also, thermoplastics are extremely light. This family of polymer resins cuts major pounds out of any application, so those in which weight is a factor are especially well suited to this material. Moreover, they display no stress or wear when heated and cooled multiple times.

Gears can be made of thermoplastics in one of two ways:

They can be machined the same way gears made of metal alloys can be. Shaping the plastic results in a finished part with precise lines and angles.
Thermoplastic gears can instead be made through injection molding. This means funneling liquid plastic into a mold, akin to how cast iron parts are made. Once it hardens, the mold is removed.

There are several types of plastic, two of the most common of which are polyacetal and polyoxymethylene. Both can be used to make gears of all types.

Gear Material Design & Selection

As with almost anything in life, the best material for your gears will depend on your intended purpose. That includes a huge range of factors. Some of the most common questions to ask before deciding on a material are:

Where are you working and what environmental factors will come into play?
Is your application hot or cold?
Is it high-speed?
Does your gear need to continually self-lubricate?
Which is more important, ductility or hardness? (This question is also applicable to other competing factors, such as whether heat resistance or compressive force are more important, etc.)
Are microbes a factor?
How much wear will your gear receive, and in what period of time will the wear occur?
What is your budget overall? What is your budget for a specific gear?
Are your gears of standard size?
Do you have your own blueprint, or do you need one made or reverse engineered?
Are oxidization, corrosion or magnetic fields an issue?

If you cannot answer all of these questions, that’s fine. More importantly, if you can answer them but have no idea what that means for gear materials, that’s also fine. A qualified gear materials specialist can help you talk through your machine and/or application to find the one that will work best for you. From brass to plastics, iron to tool alloys, we have every gear material you might need to get your project done.

The only thing that remains is to get in touch.

Get in Touch to Learn More About the Best Alloy Steel for Gears Today

Here at Illinois Pulley & Gear, our team is here to serve. We have more than 15 years in business and more than 90 years’ combined professional experience in the field of gears and pulleys. Our precision machining services encompass a variety of applications, materials, industries, and customers – and we would love to add you to our list.

Whether you have a question about gear materials or anything else, we invite you to get in touch. Our goal is to provide the highest-quality products on the market, with efficiency and economy. From automotive to agricultural, aerospace to automation, we’re here for you. Give us a call at 847-407-9595 or simply reach out today. We look forward to hearing from you.