I've given up on mist coolant - It might seem the more convenient than flood coolant at first glance but my experience has taught me that it causes more problems than it solves.

1. It doesn't matter what sort of droplet size you're getting from your mist system, if you're using a high speed spindle, the droplets atomise as soon as they hit the cutter and fogging becomes unavoidable. Decent forced ventilation becomes a necessity unless you want to end up with some sort of lung disease or an explosion.

2. Depending on what cutting fluid you are using and the humidity of the climate you are in (the UK is quite humid), the air supply to the mist system will need to be suitably desiccated to prevent moisture getting into cutting fluid reservoir. Moisture can end up emulsifying with the cutting fluid causing it to clump up and cause blockages.

3. In order to clear chips effectively, mist systems get through a lot of air - be prepared to put up with a lot of noise from your compressor, make sure its up to the duty cycle and can deliver the flow. My old compressor (now dead) would run pretty much continuously whilst the mill was running. As I did not have a separate room for it, this was incredibly irritating and didn't do my electricity bill any favours. Ultimately, I think the demands my mist system put on my compressor lead to its premature death.

No doubt, there are plenty of people out there who have had better luck than me using mist cooling, but I'm done with it. I also appreciate that it is not always practical to use flood coolant on some machines. In my case, however, fitting flood coolant isn't a problem and the resultant mess is easier to tame than atomised coolant floating about the shop, getting into all sorts of places it shouldn't. Running flood coolant is also quieter, more effective at clearing chips and uses less power.

With regards to just using cold air, I've never had much luck cutting aluminium dry. I use uncoated carbide tooling and regardless of what speed I'm cutting at, I always end up clogging my cutters without some sort of lubrication present.

Matt.