In standard convention, if memory serves, the basic axes are X, Y, and Z with the additional axes identified by number. On a mill, or HMC/VMC, the primary rotary axis is called the 4th axis, and if the mill spindle articulates, you gain another, and if the rotary axis in mounted on trunion table, you gain yet another. Sub spindles and live tooling on lathes and powered tailstocks just keep adding. Plus the main spindle can be used with a control as an axis of its own. I've not been around anything with more than 7 that I can remember, and that was at a Halliburton internal shop. I really don't know what the limit is. Never thought about it or talked with anyone about it. Not long after that project we took from HES's shop, we bought a similar machine. Theirs was a Integrex of some series. Been too long. I know we sent a couple of guys for a couple of weeks of training on a 7 axis(I believe) machine once. Machine was over a million and the software to program is came to around 100k for 2 1/2 seats. Very sweet machine. I have some pictures somewhere, but with about 70,000 in my collection they would be hard to find. They aren't organized well.