How Do Variable End Mills Work?

[Geoffrey Less]

Machining can be a loud and slow process. Metal cutting into metal at high speeds is a loud and violent process. If pushed too quickly or run at too high a speed, your cutting tools can quickly break or wear down, potentially damaging your tools and your workpiece. The variable end mill was designed to run faster than other tools without creating nearly as much chatter.

Tool chatter is the sound that is produced by machining. This is influenced by a number of factors, but is mostly affected by tool speed. The faster a tool spins, the more it will naturally oscillate. Image spinning a piece of string between your palms. The faster you go, the more the string spins out away from its central axis. The same thing is happening to your tools but on a much smaller scale.

As the tool oscillates, you will begin to hear the chatter caused by the tiny changes in impact pressure across your work area. Not only is this sonically unpleasant, but it can also potentially damage your equipment. Most operator’s solution to chatter is to lower the speeds and feeds used during production, but this comes with the cost of slowing down production. One other way to combat this issue is the use of variable end mills.

Variable end mills are designed to address the issue of tool chatter for CNC machining in a unique way. Instead of having perfectly uniform flute spacing, i.e. 90 degrees between the cutting edges of a four flute mill, the cutting edges are all spaces with slight asymmetry. This helps to prevent tool chatter by avoiding the other source of tool oscillation, the regular timing between cuts.

To give another simple analogy, imagine pushing a child on a swing. If you apply the same amount of force at the same time interval, the arc of the swing will continue to grow and grow at a predictable rate. The striking of cutting edges against the workpiece at regular intervals does the same thing to the oscillation of your milling cutters, building it constantly.

Instead of relying on even spaced flutes, variable end mills use a different tool design with irregular spacing to change the timing between strikes. This helps to break the end mill’s ability to oscillate and provides the ability for users to speed up production without creating more deafening tool chatter.

If you are looking to cut down on production times and chatter, variable end mills could be the perfect tool for your shop. If you are looking for an American manufacturer of high quality drill bits and end mills, including variable helix end mills, Online Carbide has the tools you need. Their solid carbide end mills are precision machined from high quality stock and they provide incredible results. If you have any questions about any of the tools they offer, feel free to reach out to a member of their team by calling 630.238.1424 or sending an email to [e-mail].