Making the Right Choice When it Comes to End Mill Flute Count

by startoolinc | Last Updated: January 22, 2020

There is a vast array of small yet essential decisions that have to be made when working in CNC machining. It is vital to choose the right number of flutes on end mills for smooth operation and maximize productivity. End mill flute counts are decided on several factors. These include the hardness of the material you are cutting, as well as the parameters of the end mill at your disposal.

Why Does End Mill Flute Count Matter?

The general correlation between flute count, core size, and tool strength are straightforward. More flutes equal a larger core, which equals greater tool strength. Furthermore, end mills with higher flute counts tend to have a smaller cut depth so they can be used to provide a smoother finish on virtually any material.

However, adding more flutes is not without drawbacks. A larger core takes up space and limits flute valleys that otherwise allow chips to evacuate more easily while machining. As a result, stronger end mills with higher flute counts should be used when cutting harder, ferrous materials that require a faster rate of metal removal.

Optimal flute count also depends upon the specific machining application in question. An end mill with a higher flute count is optimal in finishing applications. This is because smaller amounts of material will be removed, and chip evacuation will not be a primary concern. However, roughing operations will benefit from a lower flute count, where it is necessary to have a larger flute valley to evacuate chips with increased frequency. The implementation of ‘chip breakers’ can also be beneficial for roughing operations.

Traditional End Mill Flute Count by Machining Application

Most end mill flutes traditionally come in 2 or 4 flute variations. 2-flute end mills have generally been preferred when machining aluminum materials since the extra space is necessary for the relatively larger chips to evacuate when the tool is operating at a faster feed.

Meanwhile, 4-flute end mills have been preferred when machining steel and similarly hard alloys since they have more cutting surfaces to contact the part per rotation. Since such harder metals require a slower feed, using end mills with four or more flutes assists in increasing the rate of metal removal.

Other End Mill Flute Count Variations

Today, it is also possible to order end mills with 3, 5, 6, or even 7 flute configurations. 3-flute carbide end mills have gained popularity when cutting aluminum or non-ferrous materials, offering superior productivity and finish as compared to traditional 2-flute end mills without obstructing chip evacuation.

End mills with higher counts of 5, 6, and 7 flutes are increasingly being used to cut harder materials, as a higher flute count allows for a tool with more strength and less wear, resulting in longer tool life. High flute counts can also be beneficial in specialty applications when dealing with certain kinds of ferrous materials, such as titanium and inconel, for example.

How Many Flutes Is Right For You?

To recap, more flutes on end mills means more strength and a smoother finish. However, lighter metals may require a lower flute count to be sure that any chips have space to clear during operation.