Steve
Hope you don't mind me repeating your question but I would be interested to know if anyone has suggested a good alternative to soluble cutting oil. I know it is an old chestnut but I am in the same boat as yourself, I prefer using coolant but the machines do get left some time between use.
Having become fed up with the staining, coagulation and smell of time expired "suds" I went for some of the neat cutting oil supplied by one of the large machine importers. I am not totally convinced that it is the best alternative that we can find. It appears to cause the tools to rub rather than cut and when working the machine hard the place fills up with smoke. It is also a bit more viscous than soluble oil and thus more difficult to clean up if necessary and can seem to take an age to drain to the tank. Still things don't go rusty or black - just a sort of dark brown colour. Unpleasant enough for me to have drained the tank and returned to the jam jar and brush.
I seem to remember a couple of years ago at work they changed some machines to a blue/green fluid that everyone seemed happy with, unfortunately I was no longer directly involved and can't remember what it was. I suppose if it is a synthetic/semisynthetic then it will be expensive or only available by bulk tanker load. I know it is a different problem than you professionals face but any clues? I much prefer the primarily cooling affect of water based fluids rather than the lubrication bias of neat oils.
So, how about it guys, am I destined to "dry cut with carbide" or "splash messy thick oil all over with a brush". I'm not sure about mist systems when the machine is open (and I'm close) as not breathing appears to be a technique without much future. Perhaps the perfect cutting fluid is yet another "holy grail"; I would appreciate your views.
Best regards Keith