Hey there, if you’re here, odds are you’ve either got a part that needs machining, a project where off-the-shelf parts just won’t cut it, or you’re just starting to dig into how CNC machining works. As a CNC parts supplier, I get asked all the time: “What materials do you actually use for CNC parts?” Like, I know it’s easy to see a million part listings and go “wait, is aluminum the only thing? No way.” Spoiler: it’s not. Over the 10+ years I’ve been in this game, I’ve worked with every material under the sun, and I’ve learned that picking the right one isn’t just about price—it’s about what your part’s gonna do. Is it holding up in a hot engine? Is it going on a medical device that touches skin? Is it a random bracket that just needs to hold a shelf? Let’s break down the most common ones we deal with daily, no fancy jargon just straight talk. CNC Parts
First up, aluminum. This is like the workhorse of CNC parts, right? It’s the one we reach for 70% of the time, easy. Why? Because it’s cheap, it machines like a dream—you don’t have to crank the CNC machine super hard to cut it, it doesn’t gum up tools, and it’s lightweight. Oh, and it’s strong for its weight, which is why it’s everywhere: aerospace parts, consumer electronics (hello, your iPhone frame), automotive brackets, even custom bike parts. Wait, but not all aluminum is the same. The most common grades we use are 6061 and 7075. 6061 is the general-purpose one—great for most stuff, weldable, corrosion-resistant (we usually throw an anodized finish on it if it needs extra scratch protection), and it’s not crazy expensive. That’s the one we recommend 9 times out of 10 for beginners or people who just need a solid part without overpaying. 7075 is the tough guy—way stronger than 6061, almost as strong as steel, but still lighter. We use that for high-stress stuff, like aerospace components or racing parts, but it’s way harder to machine, so it costs more and takes a little longer. Pro tip from us: if your part isn’t under constant heavy stress, stick with 6061. Save the 7075 for when you really need it.
Next, steel. Wait, not just plain steel—there are so many types, and it’s another big one we use a ton. Steel is way stronger than aluminum, so it’s for parts that need to hold a lot of weight or take abuse. The most common steel grade we work with is A36, which is low-carbon steel. It’s cheap, easy to machine, and great for things like brackets, supports, or frames that don’t need super high strength. But it rusts like crazy if you leave it out, so we always add a finish—powder coating, zinc plating, whatever—unless you’re fine with a raw metal look that’ll turn brown after a month. Then there’s 303 and 304 stainless steel. 304 is the workhorse stainless—corrosion-resistant, non-magnetic, great for parts that touch food or chemicals, like valves, hardware for kitchens, or medical equipment parts. It’s a bit harder to machine than A36, so it’s pricier, but worth it for the resistance. 303 is the free-machining version of 304—has additives that make it easier to cut, so we use that for small, detailed parts where precision matters, like screws or pins. Then there’s tool steel, like D2 or H13. Those are for parts that need to be super hard and durable, like molds, cutting tools, or high-wear parts. They’re way more expensive, and take forever to machine because they’re so tough, but when you need something that won’t wear out, tool steel is the way to go. Fair warning though—raw tool steel is super brittle, so it’s not good for parts that get dropped or hit hard.
Moving on to plastics. A lot of people don’t realize how much we machine plastic parts, but it’s huge. Plastics are lightweight, corrosion-resistant, non-conductive, and cheap, so they’re perfect for all kinds of stuff where metal is overkill. The top plastic we use is ABS, right? That’s the stuff Lego is made of, for reference. ABS is rigid, impact-resistant, easy to machine, and cheap. We use it for everything from custom enclosures for electronics to prototype parts. It can be a bit flimsy if you need something super strong, though. Next up, acrylic (also called PMMA). Acrylic is clear, which is why it’s for display cases, windows, or parts where you need visibility. It’s easy to machine, but it scratches super easily—we have to be careful with tool speeds and finishes, and we always recommend a polished edge if it’s going to be seen. It’s also way more brittle than ABS, so it cracks if you drop it. Then there’s Delrin (acetal) — that’s a fan favorite. It’s rigid, low-friction, doesn’t wear out fast, and it’s self-lubricating. Oh, that’s a big one. If you need a part that slides against another part, like gears, bushings, or bearings, Delrin is the go-to. It’s more expensive than ABS, but way worth it for those applications. And lastly for plastics, nylon. Nylon is super strong, flexible, and impact-resistant. It’s similar to Delrin but not as slippery, and it can handle higher temperatures. We use nylon for parts that need a bit of give, like hinges or parts that will flex occasionally. Just a heads up: some nylon grades absorb water, so if your part is going to be in a humid or wet environment, make sure you get a water-resistant grade.
Wait, what about the more exotic stuff? Because sometimes regular metal and plastic just won’t cut it. Like brass. Brass is a copper-zinc alloy, super easy to machine, has that nice gold color, and it’s corrosion-resistant. We use it for small, detailed parts—like fittings, connectors, or decorative hardware. It’s pricier than aluminum, but it’s way easier to work with than stainless, so it’s perfect for tiny parts that need precision. Then there’s copper. Copper is mostly used for electrical parts, right? Because it’s an amazing conductor of electricity and heat. We make bus bars, heat sinks, or electrical connectors out of copper. It machines well, but it’s soft, so it can deform if you apply too much pressure. And then there’s titanium. Titanium is the fancy one—light, super strong, corrosion-resistant, way stronger than aluminum, and it’s bio-compatible. That’s why it’s everywhere in medical devices, aerospace, and high-end racing parts. But it’s a pain to machine—way more expensive than any other material, it eats up tools like crazy, and it takes forever. We only work with titanium when a customer specifically needs it for a critical application—like a hip implant or a race car part that needs to be light and tough. You don’t want to use titanium for a random bracket, trust me. It’s overkill and way too expensive.
Now, let’s talk about when to use what, because that’s the part most people struggle with. Last month, I had a customer come to us needing a bracket for a robot arm. They first wanted aluminum, but the arm was going to hold 50 pounds, so we told them A36 steel would be cheaper and stronger. Another customer needed a gear for a small toy—ABS would have been too flimsy, so we recommended Delrin, which lasted 10 times longer than any other plastic they tried. And a medical client needed a part that would be sterilized 100 times a year—we went with 316 stainless steel, which is even more corrosion-resistant than 304, because it can handle autoclaving.
Wait, I should also mention prototype parts, because a lot of first-timers are making prototypes and don’t know what to use. For prototypes, we almost always recommend aluminum or ABS. They’re cheap, machine fast, and you can test the part quickly. If you need a prototype that looks like the final product, maybe use a higher grade, but for testing fit and function, aluminum 6061 or ABS is perfect. No need to waste money on titanium for a prototype that’s just going to be discarded after testing.
Common mistakes I see people make: picking the cheapest material without thinking about the application, or picking a material that’s overkill. Like, last quarter a customer came to us with a part that was just a shelf bracket, and they wanted it in titanium. I had to talk them down—titanium would have cost 10 times more than steel, and the bracket would have never needed that kind of strength. Another mistake: not thinking about finishes. Like, aluminum is great, but if you need it to not rust, you need anodizing. Raw steel will rust in a week if left outside. Most materials don’t come ready for harsh environments out of the box—you have to add a finish, and that’s part of the cost, too.
As a CNC parts supplier, our whole job is to help you pick the right material, not just machine whatever you ask for. We’ve seen too many people waste money on the wrong material, or end up with a part that breaks because they picked the wrong stuff. So if you’re working on a project, whether it’s a small hobby thing or a big industrial part, don’t guess at materials. Shoot us a message, tell us what your part is going to do, what environment it’s in, how many you need, and we’ll walk you through the best options, the costs, the lead times—all of it. No pushy sales stuff, just straight answers from people who’ve been doing this for years and know what works.
At the end of the day, the material you pick is the foundation of your CNC part. You can have the most precise machining in the world, but if you used the wrong material, your part is going to fail. Whether it’s aluminum, steel, plastic, or something more exotic, there’s a perfect material for every job. Don’t overcomplicate it, but don’t cut corners on the material either. If you need help figuring it out, we’re here. Hit us up to discuss your next CNC part project—we’re happy to help you get exactly what you need, on time, and within budget.
Five-axis Machining References:
- Kalpakjian, S., & Schmid, S. R. (2020). Manufacturing Processes for Engineering Materials. Pearson Education.
- State Manufacturing Council. (2022). CNC Machining Material Selection Guide. National Association of Manufacturers.
- American Society for Metals. (2021). Metals Handbook: Volume 2 – Properties and Selection: Nonferrous Alloys and Special-Purpose Materials. ASM International.
- Plastics Industry Association. (2023). CNC Machining of Thermoplastics: Best Practices and Material Properties. PIA.
- Aerospace Industries Association. (2022). Materials for Aerospace CNC Components: Performance Standards. AIA.
Dongguan Tuoyue Hardware Technology Co., Ltd.
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