Thread: Mist Coolant systems

Love your work BobL and I'm keen to do something along similar lines. BUT, is this actually a mist coolant system or a mist lubricating system?

My understanding of the eBay misters is that they use the latent heat of evaporation of water to chill the compressed air. Water has a very high latent heat of evaporation (he=2257 kJ/kg), but kerosene (he=251) is significantly lower. I suspect ATF is lower still. So I
see your setup as more of a lubrication system without the drawbacks of a flood coolant system. Is that what you're trying to achieve? If you want more cooling effect metho has an he of 846. I don't know if ATF is soluble in alcohol though. Anyway, keep us posted.

https://www.engineeringtoolbox.com/f...eat-d_147.html

Originally Posted by jack620

Love your work BobL and I'm keen to do something along similar lines. BUT, is this actually a mist coolant system or a mist lubricating system?

Yes I'd say with ATF it's more of a lube system than a cooling by evaporation system.
With the ATF the primary idea is to reduce friction to reduce heating.
The kool-misters (Kool Mist - Kool Mist Formula "77" for Tougher Service Spray Mist Coolant Systems, Mill Coolant, Tool Coolant, Lathe Coolant, Machining Coolant) are sold to be used with a proprietary water soluble coolant containing
20-40% Triethanolamine, TEA
1 - 5% Poly(ethylene glycol-ran-propylene glycol) monobutyl ether

The nominal dilution is 20:1 so the primary coolant is water. Both these chemicals are not good but the small amounts used and the high dilution in water is what brings them into the safe level. Never the less I'd recommend using plenty of ventilation.

Interestingly even the Koolmist website says
"All components for Formula "78" are dissipated into the atmosphere by cutter heat except on; a chemically compounded lubricant that clings to the tool to reduce friction, the prime cause of heat."
Presumably the residual oil is the Poly(ethylene glycol-ran-propylene glycol) monobutyl ether.

It's dead easy to swap the ATF bottle around for a water bottle or a soluble oil/water mix.
I have a spare misting head so I can try it out with water to see what the chilling effect is.
I doubt it will be that much because the air flow used is quite small.

I wanted to avoid being tied into purchasing coolant lube as much as possible and avoid getting coolant flung all over the shed.

You've convinced me Bob. I've ordered a Noga mini-cool mister and a gallon of Kool Mist #77. I think I'm definitely going to need cooling for machining the titanium I've got coming.

Hi Guys,

I have tried a pressurised spray bottle, with various liquids...

Sorry ! But I've gone back to the dip, dab, brush, repeat as needed on both lathe and mill.

Originally Posted by BaronJ

Sorry ! But I've gone back to the dip, dab, brush, repeat as needed on both lathe and mill.

What liquids di you try and what are you now dabbing on?

Hi Bob, Guys,

I'm using diesel/kerosene for alloys, Trefolex/Temaxol for steel. I also use straight cutting oil for finishing cuts on steel.

I've also used WD40 and wax for aluminium when cutting with the chop saw, 10" inch blade at 2800 rpm, 120 zero rake carbide teeth.
The WD40 is much better than the wax. I have tried the wax when cutting or tapping steel. Its rubbish, might as well not bother. The work just doesn't get hot enough to allow the wax to work.

The best spray on lubricant I tried was 50/50 cutting oil and water ! If you don't wipe down after using it the water causes rust stains, simply because the spray gets all over, its hard to contain it. I was going to try ATF and paraffin, but never got around to it.

About breathing oil mists. They do cause respiratory issues that should not be taken lightly. One of the long time machine operators where I worked had such bad breathing difficulties from breathing coolant mist that he was off work for over almost a year until he was better. When he came back his condition returned within days and he was pensioned off on Workman's Compensation. I pulled the oil mist exposure limits for British Columbia, the province I worked in. These limits are very similar to the exposures allowed for metal dust and appropriate precautions should be taken. The safety data sheets for the coolants should be followed. I doubt your regulations would be much different. BobL can weigh in as this is more in his wheelhouse.

Oil mist - mineral, mildly refined.... TWA 0.2 mg/m3


Oil mist - mineral, severely refined .... TWA 1 mg/m3


Vegetable oil, Mist, Respirable, except castor, cashew nut, or similarirritating oil.... TWA 3 mg/m3







Pete

Originally Posted by QC Inspector

Oil mist - mineral, mildly refined.... TWA 0.2 mg/m3
Oil mist - mineral, severely refined .... TWA 1 mg/m3
Vegetable oil, Mist, Respirable, except castor, cashew nut, or similar irritating oil.... TWA 3 mg/m3

FWIW, the Kero I'm using has a TWA of 350 mg/m^3 and the ATF TWA is 5 mg/m^3.
ATF is a relatively inert oil and classed only as an irritant although I doubt any real detailed research has been done on it.
These are Time Weighted Averages over 8 hours and given the long setup times (especially in DIY operations) involved in milling/turning the ratio of vapour generation time to non vapour generation time is likely to be low.

The TWA for ATF is similar to the old OHS TWA for north american softwoods (ie 5 mg/m^3)
However the rate of ATF mist/vapour production will be in the 200 mg/min range, where as for timber processing using larger machines it will be more like 200mg/s which is why high volume extraction is needed for wood dust.

I've done some BOTE (back of the envelope) calcs that I won't bore you all with and it appears that in a smallish DIY shed even a bathroom extraction fan could provide safe levels of operation, so my 1600 CFM of extraction will easily cope with the small size and amount of milling I do.

Oil mists will behave similar to fine wood dust so in still air like a shed will also eventually settle out of the air depending on their density. ATF mist has a similar density to fine hardwood dust so it will settle at about the same rate. This means even in sheds with no extraction the mist will self clear over time so irregular operators should not be constantly exposed to high levels of mist.

OTOH if you are constantly milling/turning on high rotation then I would definitely recommend extraction of some kind. Maybe even consider installing an elephant trunk type extractor that removes the mist/vapour at close to the source. The other (less desirable IMHO) solution if you are worried is of course a vapour mask.

BobL
what do you use for flood ?

Originally Posted by eskimo

BobL
what do you use for flood ?

On the lathe and bandsaw I used the old H&F water soluble oil coolant but it needed a 1:6 dilution to prevent rust.
The I got hold of some ROCOL and that only needed 20:1 to prevent rust but it is expensive (~3x the H&F coolant) so there's no real benefit in going with it. Some of the newer ROCOL is up to 60:1 dilution.
The newer H&F stuff (XDP) is supposed to prevent rust even at 20:1 but I haven't tried it.
The undiluted XDP only has a shelf life in a sealed container of 2 years.

On the mill I have "used ATF" set up as the flood.

Last Monday I finally got around to picking up the 20L of used ATF from my mechanic mate and set up a basic filtration system for it.

So, old 20L yellow (diesel) plastic carboy on floor as a receiver, and the 20L drum of the used ATF on the WW bench. In between I had a 40mm diameter 450 mm long SS tube packed with 100mm of superfine steel wool near the outlet. After filling the SS tube with ATF, it was a matter of adjusting the flow out of the ATF drum to be slightly less than what was coming out from the steel wool plug. The flow is small, almost the thinnest dribble ATF can form without turning unto drops. All worked well for a couple of hours and so I felt comfortable leaving it but at 8:30pm I thought I better check it before bedtime and lucky I did because something had partially blocked the steel wool filter and about 100 mL of ATF had spilled onto the floor.

Yesterday I restarted the process and got through the entire 20L by late afternoon. When I finished I noticed a small (a few mL) patch of ATF under receiver and on the shed floor but thought is was from the day before spill so put the lid on the receiver and left it. I almost put it under the house which is where I store all my ils.
This morning came into the shed and there was about 2L of ATF across about a 2 x 1m patch on the floor! Just to make things interesting about a third of the oil patch was under my WW bench. It turned out that the receiver had a 5 mm long fine crack on the bottom and sealing the lid must have pressurised it enough to drive out the ATF. As soon as I released the pressure the outward flow from the crack almost stopped. Luckily I had cleaned out the drum the used ATF came in so was able to pour the remaining filtered ATF back into that drum.

I dumped a bucket of sawdust from my dust extractor onto the oil patch and left it for an hour to soak up and just finished cleaning it. Still a lot of crouching and kneeling to pick up teh sodden sawdust and wipe the floor with turps. Now my right knee is stuffed for the rest of the day and maybe even tomorrow.

Hi BobL
I understand the mess that ATF oil can make, it spreads like a wildfire. I bumped a 500ml oil can over that I had almost filled on my bench and when it hit the floor the oil out exploded like a bomb. Like you I had a bag of sawdust but it still took ages to clean it up. When I first started using used ATF oil I rigged up a pump and automotive oil filter and ran my first 20 litres through it. I cut the filter open and found very little inside it. Since then I have just let the 20 litre drums sit for a few weeks/ months and only draw oil from the top.When I use it to flood cool on the mill I am sure it is picking up minute metal particles and taking them back to the mills sump where they can settle out just like any other coolant does. Initially on my mist set up I used new ATF/Kerosine mix thinking that the fine needle may have problems with second hand oil. As I have used it a now for quite awhile on both mill and lathe I find that I do not use an extremely fine mist that can drift away but small droplets. The unfiltered ATF/Kero mix has not caused any problems.
Bob

Originally Posted by krisfarm

Hi BobL
I understand the mess that ATF oil can make, it spreads like a wildfire. I bumped a 500ml oil can over that I had almost filled on my bench and when it hit the floor the oil out exploded like a bomb. Like you I had a bag of sawdust but it still took ages to clean it up. When I first started using used ATF oil I rigged up a pump and automotive oil filter and ran my first 20 litres through it. I cut the filter open and found very little inside it. Since then I have just let the 20 litre drums sit for a few weeks/ months and only draw oil from the top.When I use it to flood cool on the mill I am sure it is picking up minute metal particles and taking them back to the mills sump where they can settle out just like any other coolant does. Initially on my mist set up I used new ATF/Kerosine mix thinking that the fine needle may have problems with second hand oil. As I have used it a now for quite awhile on both mill and lathe I find that I do not use an extremely fine mist that can drift away but small droplets. The unfiltered ATF/Kero mix has not caused any problems.
Bob

Thanks Bob.
An inspection of the steel wool filter showed my used ATF had some mm size pieces of plastic, squishier stuff that looked like cork, maybe bits of a gasket? and some black mm size flecks I could not identify - could be paint? It was the plastic that I think blocked the filter. From now on I will just do what are doing , let it settle and draw from the top of the drum

For the mist cooler on the mill I bought a 1L of the cheapest ATF I could find at Supercheapauto and it cost $5. I emptied that into a 1L transparent PET bottle and after about 10 hours of mill use I have only used about 100mL of ATF. My original estimate was it would also me for 80 hours of milling but it looks like it could be longer. Of course usage will depend on what is being milled but I'm thinking it's not going to be worth mucking about with used ATF for the mister.

I use an air blast to clear the chips with a pulsed mist to lubricate the cutter. I find 3 parts kero to 1 part cheap olive oil works fine and is very bio-compatible. The pulsed kero evaporates fast and can't be smelt. It probably also cools the cutter. The parts come out dry. Consumption is micro.

I don't/won't use commercial coolants as they either go off or rot your skin.

Cheers
Roger

Originally Posted by rcaffin

I use an air blast to clear the chips with a pulsed mist to lubricate the cutter. I find 3 parts kero to 1 part cheap olive oil works fine and is very bio-compatible. The pulsed kero evaporates fast and can't be smelt. It probably also cools the cutter. The parts come out dry. Consumption is micro.

Interesting brew there. I was thinking of upping the kero fraction in my mixture.

Your brew sounds a bit like my one part diesel and 3 parts canola I used for a while on the auxiliary oiler on my chainsaw mills. What made that attractive was that canola could be bought for <$3/L whereas chainsaw bar oil was a lot more. I eventually gave up on that because after 3-4 years the drying canola started forming a tacky film over everything that made a real mess and was hard to wash off. Eventually I found a place that sold cheap bar oil for ~$2.50/L and haven't used teh canola since

I don't/won't use commercial coolants as they either go off or rot your skin.

I haven't ever had skin problems, and since using an aerating pumping system have not had any coolant go off. The main reason for going to misting for me is not having to clean out suds tanks.