Diamond Cutting Tools: Your New Best Friend?

By Don Graham, Manager of Education and Technical Services

Marilyn Monroe sang about diamonds being a girl’s best friend, but if you’re machining high-performance parts from advanced non-ferrous materials, these little gems could possibly be your best friend, too – especially if you’re dealing with high demands and limited capacity.

Diamond is the hardest and most abrasion resistant material known to man, making it a brilliant cutting solution for the manufacturing industry. This is especially true for the aerospace and automotive sectors where polycrystalline diamond (PCD) and diamond-coated tools can offer amazing productivity advantages through extra long tool life and extremely fast cutting parameters. In fact, a diamond coating can bring 10 times more tool life to a cemented carbide cutting tool.

Overall, diamond tooling takes machining to levels of performance that carbide simply cannot go, significantly reducing the frequency of tool replacements and enabling machines to make parts at much higher rates. It is important, however, to remember that while the upfront cost of diamond tooling can cause sticker shock, the long-term benefits of these solutions can bring some serious bling to a bottom line.

Let’s suppose you’re using carbide tooling to machine aluminum at 2,000 surface feed per minute. By switching to diamond tooling, you have a solution that will last for what seems like forever and can machine as high as 10,000 surface feed per minute. This results in you machining five times as many parts in the same amount of time with the same number of machines and operators as before.

As such, your cost per part drops dramatically, and you can do one of two things. You can either make a lot more profit per part, or you can reduce the selling price of each part to enable your company to gain increased market share. Keep in mind, the latter choice would help keep more manufacturing jobs here in the United States as opposed to going overseas.    

If you think diamond tooling could be your new best friend, here are some things you should first consider:   

• The biggest payback from using diamond tools comes with machining abrasive materials. For example, the aluminum automotive manufacturers use to build engine blocks is very abrasive, having silicon and silicon carbide particles that can really grind away at a cutting tool. With carbide tooling, these manufacturers may run at 500 surface feed per minute and get 10 minutes of tool life. Diamond tooling, on the other hand, would allow them to machine at 5,000 surface feed per minute and get a couple of hours of tool life.      

• Diamond cutting tools have a need for speed and can reach their full potential with machine tools more suitable to them. However, if these fast machines are way too expensive for a manufacturer, a slower machine equipped with diamond tooling will still achieve higher levels of productivity versus one using carbide or high-speed steel tooling.

• Preventing the aluminum from sticking to the cutting edge is important for maintaining a good surface finish. Therefore, the machine tool used in conjunction with diamond tooling should always be running fast enough to avoid metal build-up. There are also specialized coolants that can assist in preventing built-up edge.     

• Diamond tooling is not suitable for use in all materials. While aluminum, titanium, hard steels, composites and graphite materials are all appropriate for diamond tooling, steels, stainless steels and cast irons are NOT. Diamond is made out of carbon, and carbon reacts with iron to form iron carbide – essentially, it is an atomic reaction that turns diamond into pencil lead (graphite).  

• PCD tooling, which involves taking diamond particles and hot pressing them together, is more expensive than diamond-coated tooling. However, it offers higher wear resistance and yields a better surface finish than diamond-coated tooling.

• Diamond-coated carbide tooling offers better chip control and has more geometric flexibility than PCD tooling. Practically any tool shape, from endmills to turning inserts with chip grooves, can have a diamond coating. And while PCD tooling may produce better surface finishes, diamond-coated tooling is better at machining graphite components and composite materials. But like any other cutting tool, the life of a diamond-coated tool varies based on part geometry, material type, and speed and feeds.

• Twenty years ago, there was a problem with diamond coatings peeling off carbide cutting tools, creating a stigma that still exists with many manufacturers today. However, peeling is no longer an issue because cutting tool manufacturers prevent it by selecting compatible carbide chemistry as well as using suitable preparation techniques and proper reactor conditions.

• The long tool life of diamond tools make them ideal for large machining volumes or long cuts. After all, it takes a lot of cutting for a manufacturer to be able to capture all the useful life the tool can deliver.   

It’s obvious diamond cutting tools can bring clear-cut advantages to advanced part-processing applications by allowing for increased operating speeds without sacrificing tool life. And while adding these tools to your operations can be an expensive business decision right out of the gate, you will definitely benefit in the long run if your goal is to accommodate more orders or achieve greater output. If you have any questions about diamond cutting tools, please don’t hesitate to contact a Seco applications expert.

About the Author

Don is the manager of education and technical services for Seco, responsible for all educational activities for the NAFTA market, new product testing and various other technical functions. Outside of work, he enjoys making maple syrup, restoring antique tractors and farming. Contact Don at dgraham@secotools.com.