Every machinist and shop has its own way to machine its pieces. What I know to be slow or wasteful might be considered an efficient approach for the next guy. So, when giving advice about machining materials the best thing we can do is see what are the few takes most of us seem to agree upon and start building from there.
Aluminum is a favorite among those who like metal work or are used to supplying pieces for the aerospace industry. It is versatile, cost-effective, and, more importantly, easy to machine. But the fact that this material allows itself to be sculpted with relative ease, does not mean you should not get the best end mills for aluminum. However, what should you consider when working with this amazing metal?
Geometry
Machining is about getting your math right. The soft nature of aluminum makes it a pleasure to machine but also poses some serious challenges that are unique to it. Its gumminess makes the chips stick to your end mill flutes, making it difficult to evacuate them. That’s why a higher helix angle is often imperative for cutting aluminum. High helix angles push material upwards with increased force, preventing them from clogging your flutes and allowing you to drive the tool at faster feed rates. They also help your tool stay in constant contact with the piece and perform uninterrupted cuts.
Flutes
A high flute count would decrease the space the chips have to evacuate, increasing the chance for tool clog. Also, narrow valleys can cause your flutes to re-cut or chew the chips, which is usually detrimental to your part finish. So the best end mills for aluminum usually have a low flute count with wide valleys that allow your curls to pass through unimpeded.
Coatings
Coats not only protect your tool from wear and high temperatures. They also reduce friction coefficients and increase lubricity. This is extremely important when working with aluminum as hot chips tend to weld to your tools and ruin their sharpness. However, not all coatings are ideal for cutting aluminum. TiAlN coatings are a favorite among machinists as they help increase hardness and reduce tool wear. However, this specific coating material contains aluminum and tends to form an aluminum oxide coating around itself when it reaches certain temperatures, which bonds with your work material causing your tool and the piece to stick together and create a buildup edge along the tool. That´s a no-no.
For this kind of job, you need coatings created specifically for machining aluminum. Zirconium nitride or ZrN coatings increase the refractory properties of your tool and have an incredible resistance to erosion. This special coating is applied on tools through physical vapor deposition on high-end tools, so they form a thin coat that does not affect sharpness but enhances lubricity for increased chip flow.
Substrate
The substrate is the core material of your tool. Since you want to be able to run your tool for long periods and uninterrupted cuts, you need a material that holds its sharpness like no other. Steel tools are usually very sharp, however, they lose their luster pretty quickly, and, as soon as they reach certain temperatures, steel enters a tempering process.
That’s why the best end mills for aluminum are made of carbide. This super composite material stays sharp longer and can withstand incredibly high temperatures. While solid carbide is brittle, the soft nature of aluminum makes it ideal for aggressive tool paths and feed rates without risk.
The only problem with carbide tools is that they tend to be a bit pricey. However, you can find incredible deals in carbide cutting tools by directly contacting Online Carbide. They cut the middle man and offer manufacturers direct prices on all of their high-end cutting tools. Visit them today or contact them at sales@onlinecarbide.com.
