Soluble v straight cutting oil in low humidity

Hi All,
I live in the AZ High Desert and it is very low humidity (a bit high at 31% at the moment) all year round. I have to replenish the water/
oil mix regularly as the water evaporates out pretty quickly. I was about to order some more soluble cutting oil and thought I would ask here first.
I am wondering if a straight cutting oil like Mobil 404 would last longer, maybe indefinitely. I mostly cut aluminum on mills and lathes so do not want any staining after machining.
Anyone have some low-cost favorite cutting oils?
Thanks
Dave
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On 07/21/2010 10:32 AM, Dave, I can't do that wrote:

Do you have to replenish the water/oil, or do you just need to add distilled water to replace what was lost?
--

Tim Wescott
Wescott Design Services
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Hi Tim,

When the water evaporates it leaves a brown oil slick on the surface that really does not mix back in very well so I skim that off. I usually mix up a fresh gallon and pour it in the tank to make up the level.
Using distilled water is a bit extreme though??? <grin>
Dave
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Is there a way to better seal the tank? My grinder has a 40 gal tank and I don't get any evaporation but we have to add a preservative or it gets stinky.
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Hmm, not really the tank is pretty well sealed in the machine base, probably 30+ gallons. The evaporation must be happening on the table as that's the only time the fluid is exposed. The table drains have hoses that take it straight back to the sump. We almost never have overflowing into the base tray.
As for stinky, try using a fish-tank bubble from a pet store. It oxygenates the water and stops the bacteria stagnating. Have not had to use "the pill" for years.
Dave
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On Fri, 23 Jul 2010 13:13:41 -0700 (PDT), "Dave, I can't do that"

Ayup. A cheap 110vt timer works great and you only need to run it about 3 hours a day in actuality. Timers are about $6 at Kmart etc etc if that much.
Gunner
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Actually even 15 minutes per day solves the problem.
i
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