[We have a slew of changes and clarifications to metal shop procedures forthcoming soon; here is the first. These will be included in a new Metal Shop Policies and Procedures document that we are creating.]
Summary: Refill low/empty cutting fluid reservoirs with pre-mixed cutting fluid (instead of distilled water).
In the past, when a cutting fluid reservoir level became too low to use a machine, we had told people to just refill it with distilled water.
While this did lead to the cutting fluid concentration dropping over time, this was much slower than you might expect, because evaporation of water from the cutting fluid over time would increase the concentration of the remainder.
At least until we got the Cold Saw. The Cold Saw gets a lot more use, so using distilled water to refill it rapidly led to the cutting fluid being too dilute. Water provides the necessary cooling for the Cold Saw but not the required blade lubrication. In addition, the cutting fluid contains some anti-corrosion components; pure water was causing machine parts to rust.
So now, when a cutting fluid reservoir becomes too low, it should be refilled with more of the pre-mixed cutting fluid. This fluid is kept in clearly labelled bottles and has a distinctive blue color. (It also marked with a note that it is not a cleaning fluid, because it looks a lot like Windex.) Bottles of this will be available in the bottom of the machine shop cabinet (by the drill press); we will also place several bottles between the Cold Saw and the Horizontal Band Saw. (These need refilling the most.)
If no pre-mixed cutting fluid is available, first notify the stewards using a red shop QR code. Be certain to state which machine was low so we can fix the fluid concentration later. Then (and only then), you can add distilled water to the reservoir to continue working.
While the Cold Saw was the impetus for this decision, it applies to all cutting fluid reservoirs except the Tormach. (The Tormach uses a different fluid.)
Additional note just for stewards: I’ve also realized that we were mixing the cutting fluid too dilutely to start with. The target Brix for the CLI Syntec is now 5.0 (this is marked on the refractometer case), and we might even consider going to 6.