An O (not zero) flute CNC router bit is a bit that is specifically designed to enhance certain materials machinability. Ouch, what did that mean. Well, lets look at it this way. When you are cutting steel with your reciprocating saw do you use a wood blade? Sometimes… Wait no. Never. You use the blade that is best designed for mitigating the properties of what you are cutting.
If you are still with me, the next question is enevitably, why? Well, an O flute Bit plays on two major factors. The first is temperature mitigation and the second is vibration, which one could argue go hand in hand. By designing a bit that has less drastic cutting edges (look at the picture above and then think of your standard 2 flute doencut bit) the bit has the ability to produce less heat. A few reasons for that, but one worth mentioning is the reduced amount of waste extracting from the cut site. There is less “fray” and that reduces heat. The second part is the design of the initial cutting edge. It’s basically flat. That combined with the shape of the flute causes (see below) very low vibration.
I think this is an easy answer, but the bottom line is that you don’t want to melt your material. With wood you would possibly have burn marks, but with plastic it would literally melt. Causing warping, design flaws, structural integrity issues and more. Chip re-welding is also an issue, that is when material you are cutting out gets hot enough that it reattaches itself to the original material before the cut is complete.
Beyond the desire not to ruin your material, many people love O flutes because it causes a mirror finish. Think of making a coin and causing the flat areas to be a perfect shiny mirror.
Link to the bit I use Amana Tool 51454-Z CNC, SC Spiral O Single Flute. And you should know that I am an affiliate marketer for ToolsToday, BUT I love their tools. I didn’t choose to do this with them because it would bring me alittle money. It was more about supporting a company that really makes some superior stuff! I love their bits, blades and everything else (I can afford).