The Home Machinist!

What is a good coolant for aluminum to be used in a mist coolant device?

As far as I'm concerned a mist system is more about lubercation rather than cooling. For real cooling you need a water based FLOOD cooling system. And if your machine is not totally enclosed a large mess is the resault ! WD-40 works well for aluminum BUT the waxy part of it makes for sticky chips that stick everywhere. For that reason I only use it when absolutey nescesary ,straight kerosene ,which is the other main thing in WD40 works well.

I'm certainly no expert, but I've read a major component of WD-40 is in fact kerosene just like John said. Apparently it goes through some type of chemical process to remove what they call aromatics that gives kerosene it's distinctive smell and additions are then made to make WD smell like it does. Overall a gallon of straight kerosene is a whole lot cheaper than a gallon of WD if your willing to tolerate the smell. Again like John said and some forum threads also have mentioned, there's no real difference between straight kerosene and WD as far as using it as a cutting fluid for aluminum. As long as you stay below it's instant smoke point for heat generated at the cutting tip, it lubricates the cutting edge, prevents chip welding and metal tearing as the cut progresses.That's what produces the much better surface finish.WD or kerosene is still a flammable, so using it in a mist coolant dispenser probably isn't a good idea since that's pretty much the same as what the injectors in a diesel engine do at a lot higher pressure. With a hot enough spark or ignition source you could end up with something you really don't want.

I'd also agree with John that these systems are more about lubrication than cooling, although there would certainly be at least some. Since I've never used one I have zero idea what would work the best. There are coolants specifically designed and meant to be used with them. I'd also read this, https://www.practicalmachinist.com/vb/c ... on-312545/ and it's only one of many about those mist coolant systems that might help. But an enclosed cnc is a whole lot different than a wide open manual machine. I fully trust Bill Shields judgement and experience and he had a bit to say on both pages of the thread here. http://www.chaski.org/homemachinist/vie ... 4&t=111303 So I'm not convinced they can be made to work well enough without an enclosure and even filtering or exhausting the residual air mist outside. It's not been mentioned on any YT video I've seen yet, but those using them on manual equipment seem to adjust down to very little coolant compared to the volume of air. I suspect that's to reduce any air borne mist to a minimum. Industry even has an acronym for that, MQL or Minimum Quantity Lubrication. If your not using it that much in a home shop it probably doesn't matter, but it's still worth knowing about. Because of the efficiency level, compressed air is still one of the most expensive forms of energy to produce and convert it into doing some type of work for you.

Do not ever atomize anything combustible unless your specific intention is an explosion

Sparks do not have to occur at the cutting interface to cause problems.

Even with fully integrated halon systems, I have seen totally enclosed CNC machines blow their exhaust fans through the ceiling before the IR detectors can dump the halon into the cabinet.

Excellent advise guys! I recently bought a mist unit and was just going to run my regular coolant through it but with a higher water ratio. Still not sure t's worth it yet on points made like sticky chips, hard to clean up and mist in the air (inhalation).

Deodorized kerosene has the stink removed and it is used for oil lamps etc. If you have one of the candle making supply craft places nearby they will likely sell it. You can also use her favourite scented lamp oil if you don't want SWMBO to gripe about the stink. A gallon of deodorized on Amazon costs a little less than a gallon of WD-40.
https://www.amazon.ca/dp/B07DD1Y7BF/ref ... NrPXRydWU=

Pete

I don't know for sure about the cheaper one's Ron, but some of the brand name (expensive) systems mentioned in that PM link I posted just might use some fancy pants flow technology to reduce that excess air misting. If you find yours doesn't do so, maybe ordering a replacement tip they use would be the cheapest way to test if they work a lot better. The air and coolant all seemed to be controlled by simple needle valves, so any mixing and mist reduction tricks would theoretically be in those tips. Fwiw, some have mentioned on YT that if you can see the coolant at all in the air stream as it exits the tip your using too much.

Good information I hadn't known about kerosene before Pete, and that it's even available stink free. Thanks for that. For some jobs like tapping, counter boring for cap screws, reaming etc in aluminum. I think that Relton aluminum specific cutting fluid I mentioned before still works better than WD. Much harder to get of course. There's a noticeable reduction in torque between the two when hand tapping and I think better surface finish. For the same volume amounts, WD is still cheaper by the gallon though. What I don't know is if that Relton product might somehow effect secondary operations like anodizing or what solvent to use to remove it well enough so it doesn't.

pete wrote: ↑Sun Jan 16, 2022 10:52 pm I don't know for sure about the cheaper one's Ron, but some of the brand name (expensive) systems mentioned in that PM link I posted just might use some fancy pants flow technology to reduce that excess air misting. If you find yours doesn't do so, maybe ordering a replacement tip they use would be the cheapest way to test if they work a lot better. The air and coolant all seemed to be controlled by simple needle valves, so any mixing and mist reduction tricks would theoretically be in those tips. Fwiw, some have mentioned on YT that if you can see the coolant at all in the air stream as it exits the tip your using too much.

Good information I hadn't known about kerosene before Pete, and that it's even available stink free. Thanks for that. For some jobs like tapping, counter boring for cap screws, reaming etc in aluminum. I think that Relton aluminum specific cutting fluid I mentioned before still works better than WD. Much harder to get of course. There's a noticeable reduction in torque between the two when hand tapping and I think better surface finish. For the same volume amounts, WD is still cheaper by the gallon though. What I don't know is if that Relton product might somehow effect secondary operations like anodizing or what solvent to use to remove it well enough so it doesn't.

Can I use Relton in a mist coolant system?

the relton (as described) that I used is too thick to put through a mister

Yep the viscosity right out of the can is as Bill said too thick. If you were to dilute it I'm unsure of what you'd use or how it would affect it's properties. My best guess is it was formulated and meant to only be applied with a brush, oil can etc. and probably thickened on purpose so it clings to the part surface or cutting tool. I don't do much in aluminum, so my can is now over 10 yrs old and whatever they were using when I bought it. With the way things get suddenly removed for safety and environmental reasons, I can't say for sure it's still the same today. So far I've seen no posts mentioning that it's been changed and now doesn't work as well. But if you buy a new can Ron I'd be interested in if it still works as well as mine does.

A good 'mister' can be adjusted to a coarse, low-velocity sputter. I disagree with Mr. Evans, because a properly set-up mist/sputter can remove a great deal of heat, to the point of keeping the tool and the workpiece cool to the touch. When I use my Noga in this manner there is almost no fogging, the air stays safe. I use Rustlik WS-5050 which seems a bit expensive but it goes a very long way.

Without a particle counter how do you know the air is safe? Particles under 10 micron are not visible and go deepest into your lungs. There are lots of under $50 particle counters available that would confirm it.

Pete