How to Choose an End Mill for Aluminum

Often when you ask five machinists the same question, you’re bound to get seven answers. That doesn’t mean that they are indecisive, but rather, it’s because there are so many different ways to do any given operation.

That being said, there is no 100% right or wrong way to cut aluminum, but here are a few things to keep your eyes on when buying end mills.

Carbide

Carbide stays sharper longer. While it might be more brittle than other end mills, we’re talking aluminum here, so carbide is great.

The biggest downside to this type of end mill is that they can get pricey. Or at least more expensive than high-speed steel. As long as you have your speeds and feeds dialed in, carbide end mills will not only cut through aluminum like butter, they will also last quite a while.

Get your hands on some carbide end mills here.

Coatings

Aluminum is soft when compared to other metals. Which means chips can clog up the flutes of your tooling, especially with deep or plunging cuts. Coatings for end mills can help alleviate the challenges that sticky aluminum can create.

Titanium aluminum nitride (AlTiN or TiAlN) coatings are slippery enough to help keep chips moving, especially if you aren’t using coolant. This coating is often used on carbide tooling.

If you’re using high-speed steel (HSS) tooling, look for coatings like titanium carbo-nitride (TiCN). That way you get the lubricity needed for aluminum, but you can spend a little less cash than on carbide.

Read: 4 Things We All Hate About Aluminum

Flutes

This is arguably the most important feature to consider when choosing an end mill for aluminum. Again, aluminum is gummy and soft, which means it tends to stick in the flutes of your end mill.

While coatings can help alleviate this issue, if you’re using a 4- or 5-flute end mill to cut aluminum, even the best coatings may not help.

One of the main goals of flutes when cutting aluminum is to clear chips. While having fewer flutes makes your tool less rigid, it also allows for more efficient movement of those chips. If you don’t get chips out of there, you risk ruining your surface finish, by re-cutting chips, or worse, destroying your end mill by friction welding the chips right to your cutter.

Your best bet for an end mill in aluminum is two or three flutes. While you can get away with more flutes, if you are really concerned about rigidity, your risk of destroying your end mill will go up.

Geometry

So much of machining is about math, and choosing an end mill is no different. While the number of flutes is an important consideration, flute geometry should also be considered.

High-helix flutes help dramatically with chip evacuation, and they also help with the cutting process. High-helix geometries have more consistent contact with your work piece… meaning, the cutter is cutting with fewer interruptions. Interrupted cuts are hard on tool life and surface finish, so using high-helix geometries allows you to stay more consistent and move chips out faster.

Interrupted cuts wreak havoc on your parts. This video shows how interrupted cuts with a chipped end mill can affect your cutting strategies.

If you’re looking to cut aluminum, fear not… it’s a forgiving material. If you want to cut aluminum better, look for end mills with high lubricity and an efficient flute design for chip evacuation. With some fine tuning in your feeds and speeds, you’ll be making piles of aluminum chips in no time.

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Chris Fox

Chris comes from a publishing background with years of experience in science, technology, and engineering publications. Previously an editor with Product Design and Development and Gizmag, he has a keen eye on the maker community and the changing landscape of the world of prototyping, product development, and small-scale manufacturing. Chris has been working with clients to create Tormach's customer success stories since 2013. Follow him on Twitter @TheChris_Fox

Chris Fox

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