I am looking at a new to me spindle with ATC for my machine. It has an air connection labeled as "Spindle Nose Pressurization". My current ATC spindle does not have this connection. The spindle is coming off a wood routing machine. The only thing I can find when I google is that it's for keeping coolant out of the spindle nose bearings. But coolant isn't used on a wood machine. So what does this do on a wood cutting spindle?