Kodiak Cutting Tools® Speeds and Feeds Blog

Cutting Tool Talk, Tips and News for Machinist, Metalworkers and Fabricators of All Kinds

question about 2 flute vs. 4 flute carbide end mill for aluminum

A customer was trying to decide whether to use a 2-flute or 4-flute carbide end mill for his job on aluminum. One important question before spending the extra money for a high-performance tool, is how many parts are you making?

 I think one you might look at is our part number 136475. This is 1/4" x 4" long with a 1" length of cut. The number of flutes is a trade-off between better finish and better chip evacuation. Sometimes with softer grades of aluminum the flutes could get clogged up, but as long as that is not an issue for you a 4 flute will give you a better finish and do more work per rotation of the tool. I think a lot of people are using this tool for doing a similar application. There is also a popular one with the gunsmiths that is specifically for aluminum. The part number is 150104 (150027 for uncoated). This is a high-performance tool that is capable of doing long production runs and much high speeds & feeds than the standard tool, but if you are not doing a large quantity it would probably be more than you need. The high performance ones have 3 flutes, a deeper clearance between the flutes for better chip evacuation and an optional ZrN coating specifically for aluminum and other non-ferrous metals. The high-performance also has a 45 degree helix instead of the standard 30 degree. This provides a better finish due to a shearing action of the flutes and also helps get the chips up and out. The main reason carbide end mills fail is when the re-cut a chip from the previous machining, so the chip evacuation is important, but if you are doing a smaller quantity you can try to use air of fluids to keep the cutting area clear from chips.


End Mills for Aluminum

A customer recently asked about what style of end mill to use for his aluminum application. Here are some general guidelines:

It is a trade-off between chip-evacuation and finish. A lot of times with aluminum the long stringy chips can clog up the flutes. This often leads to re-cutting the chip, which is the main cause of tool failure with end mills. So the chip-evacuation is important, but depending on the grade of aluminum and the cut, you could use a 4 flute. Generally, the less flutes = better chip-evacuation AND more flute = better finish/more work per rotation of tool. The aluminum cutting tools you have on this order have a higher helix angle (45 degree instead of 30 degree) which creates a better finish through more of a shearing action as the end mill cuts. The aluminum style also has deeper spaces between the flutes for better chip-evacuation. The core-diameter of the tool does not need to be as large when cutting aluminum, so this deeper flute design works well. These are high performance tools designed for maximum material removal rates and should be run at the speeds and feeds for the high performance tools on our website.