Ok, here we go again. The cabinet for Metal Nibblers One is complete, and I
am ready to add coolant. (Ok, I still have not made a door for it. I've
got sheet plastic spring clamped across the front.)

I've got misc accumulated hardware (pump, locline, barbs, hose) and can make
other stuff as needed.

I favor flood cooling. Mist cooling scares me for most coolants, and I
can't use water based coolants. I'm turning up to 30,000 rpm with an open
brush motor. There is a lot of air moving just from the spindle motor, and
there is a potential for sparks if a mist gets drawn into the motor. The
machine is mostly made of aluminum with some steel parts. Makes water based
a no go.

Options:
Regardless of what some say WD-40 makes a pretty fair coolant/lubricant for
cutting aluminum. (There does seem to be a cult following of people who
hate WD-40 unconditionally.) Fairly high flame risk, but maybe not for
flood cooling. $20/gallon

Transmission Fluid. I have no real knowledge of this. I've poured some on
a part to see and it seems to cut ok, but for short runs dry cuts ok too. I
have to wash it off with Dawn dish soap, rinse and repeat to get rid of the
oily feeling of the final work piece. Haven't really given it a fair shake
as a continuous flood coolant. $15-20/gallon

Hydraulic Oil. No kidding. One local production shop who's owner is a
fishing buddy of mine suggested that I just go buy 5 gallons of hydraulic
oil over at the local Sam's Club. $Have not checked price

Diesel. The smell gives me a headache. I do have 50 gallons of diesel on
hand to fill my tractor and its probably the cheapest answer. I have not
tried it due to the headache factor. $4/gallon

Commercial cutting oils. ??? Never bought any other than the small bottles
I use for threading manually. $(priced all over the spectrum)

High tech option (not really):
One of the super high speed machine makers says they setup their machines to
spray mist ethanol. Claim they get incredible cooling with it, and I can
believe that. $(can't even find it for sale in bulk, do not want a
flammable mist anyway.)

Not an option:
Water based and/or water soluble coolant/lubricant is not an option. There
seems to be a certain following that thinks water based in the only answer
to everything as well. Not for two out of three of my machines it isn't.
It's a no go.

I am really pushing my speed for a small machine, and may go faster. For
small circular pockets it can really shake the work bench. I bolted it
through the cabinet through the table surface, and added full length sheets
of plywood to the sides and back to brace the table for those types of cuts.
I may have to make a different more rigid work bench for it eventually. The
plywood on the sides did make a nice place to add heavy drawer slides
though. No I have a place for all those bits, mills, and tools that I only
use on that machine. LOL.