# Oh No!  Another Mister



## rdean (Jul 5, 2014)

My little mister was plugged up so I thought just take it apart and clean the nozzle.  
Very bad idea!  The tiny hose barb that the inner hose connects to broke off inside the nozzle.  I didn't want to replace the nozzle so went to HF and bought an air brush and a 10 foot air brush hose for about $20 after rebate.
I reamed a piece of pipe I had to press over the end of the air brush and tied the air brush button down.

Works great and I can't see much difference in the operation.

Thanks for looking
Ray


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## JimDawson (Jul 5, 2014)

What a great idea!  Wish I'd have thought of that one.


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## drs23 (Jul 5, 2014)

That's very clever! Great adaptation!


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## MikeWi (Jul 5, 2014)

I hate how an air brush seems so blatantly obvious now that someone else has already thought of it! LOL  Very nice!


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## Andre (Jul 5, 2014)

**headbang* *I have one....and a compressor for it.......I assure you your going to be blamed for my next set of ideas!


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## rdean (Jul 6, 2014)

Thank you all for the kind reply's.
Ray


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## Downunder Bob (Dec 6, 2016)

rdean said:


> My little mister was plugged up so I thought just take it apart and clean the nozzle.
> Very bad idea!  The tiny hose barb that the inner hose connects to broke off inside the nozzle.  I didn't want to replace the nozzle so went to HF and bought an air brush and a 10 foot air brush hose for about $20 after rebate.
> I reamed a piece of pipe I had to press over the end of the air brush and tied the air brush button down.
> 
> ...




I have never used a mister, what is the advantage, and disadvantage, Is it ok to have a lot of atomised coolant in the air of a workshop? I've only ever used flood coolant, or oil from an oil can.


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## MikeWi (Dec 7, 2016)

bobshobby said:


> I have never used a mister, what is the advantage, and disadvantage, Is it ok to have a lot of atomised coolant in the air of a workshop? I've only ever used flood coolant, or oil from an oil can.


The type we generally are referring to here in the forum is "fogless", so you won't have the coolant in the air. It uses a very fine mist of coolant and a lot of air. They work great, and don't have the mess that flood can create or the  smoke that oil can create.


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## wrat (Dec 7, 2016)

bobshobby said:


> I have never used a mister, what is the advantage, and disadvantage, Is it ok to have a lot of atomised coolant in the air of a workshop? I've only ever used flood coolant, or oil from an oil can.



The whole point of  coolant is to dissipate heat.  Any time the coolant is finely divided (mist) there's much more coolant surface area exposed to conduct that heat.  So misting is basically more efficient at getting the heat away.

If you look at the big NC machines, they all have massive cooling systems because they're going flat-out every chance they get.  So they build the machines with lots of  shielding and sealed doors to try to keep the coolant (and chips) under control.  They run coolant like a commercial dishwasher under glass.  Even THEN, the air is full of atomized coolant.

I don't know of any studies condemning the hazards of "second hand mist" so whether or not it's "ok to have a lot" is up to you, I suppose.  Surely all the alphabet agencies have weighed in on this, by now.  In the old days, nobody knew or cared.  I just know the more chips you move, the more crap will be in the air.  Of course, one machine outputs far less airborne material that a dozen machines.  So your shop will be markedly different from a big place.

And that's the catch:  even without misting, you're putting a lot of atomized chemical in the air!  Trusty ol' oil-flood coolant puts a lot of particulate and vapor into the air just from splashing.  Oil-drip causes more smoke.  The water based milk-coolants all splash, likewise.  So i've not seen a coolant of any type that will not find it's way into the air in some amount directly proportional to the amount of chips you move.

What seems to keep it down is keeping spindle speed down.  That's what i tend to do.  I've had my fill of "high speed" environments.  Production shops can't do this, of course.  They have to turn everything up to 11.  But i've seen lots of youtube vids where guys run the cutter twice or three-times as fast as I would and send smoke, chips, splashes, and vapors everywhere.  Often from only a few drops of oil.  I use lots of oil and take my time, because i'm a hobbyist now.  Truth be told, my motors probably out-gas more than my cutting does.



Wrat


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## rdean (Dec 7, 2016)

I made this over 2 years ago and it is still in use today.
I do not use any chemicals just plain water at about 20 psi with the water flow turned down so I can just see the mist.
The air pressure tends to keep the cut clear of chips too.
I have learned that for me smaller cuts and slower feeds work better and fewer broken bits.  
Most of my work on this CNC mill is with 0.125 and smaller end mills.
I have done several jobs with a 0.0315 tool making branding irons for woodworkers.

Thanks for looking

Ray


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## Reeltor (Dec 7, 2016)

rdean said:


> I made this over 2 years ago and it is still in use today.
> I do not use any chemicals just plain water at about 20 psi with the water flow turned down so I can just see the mist.
> The air pressure tends to keep the cut clear of chips too.
> I have learned that for me smaller cuts and slower feeds work better and fewer broken bits.
> ...



Don't  you get any rusting from only using water?  I use flood coolant with Kool Mist that has rust inhibitors, and it does make a mess.  I would like to change over to a mist type system but was always concerned about breathing in the mist.  As you are using smaller bits on a CNC unit, I tend to use my very old manual mill in the horizontal mode where it makes a lot of (big) chips.  What do you think?

Mike


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## RJSakowski (Dec 7, 2016)

Hot tools/parts are cooled by removing heat.  This can be done by transfer through absorption of heat to a cooler material as is done with flood coolant or by evaporative cooling as is done with mist coolant.  

The ability of a material to remove heat by absorption depends upon the specific heat  of the material (calories/ºC/gram) x the mass of the material.  Flood cooling works because the coolant has a fairly high specific heat and we flood the work area with fresh coolant. It also has a high thermal conductivity which facilitates heat transfer.

Mist coolant has a fairly high specific heat but there isn't much mass.  However, the mist coming in contact with the tooling and/or work evaporates. While the mist has a specific heat of around 1 cal/ºC/gram, it has a heat of vaporization of around 550  cal/gram and is therefore capable of efficient cooling.  The compressed air in the stream aids in chip removal.

Using oil serves primarily as a lubricant.  Its specific heat is much lower than water based coolants and its thermal conductivity is lower as well.  Its lubricity does assist, though,by reducing friction and resultant heat generation.

Using compressed air does not provide much in the way cooling by virtue of its low specific heat and low mass but it does serve another important function which is chip removal.  We  use either water or oil to quench steel to harden it because of their ability to quickly pull heat away from the steel.  Subjecting the steel to a blast of cold air simply will not do the job.


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## rdean (Dec 7, 2016)

I try to do most of my metal parts in batches making 2 to 6 identical items in a run.  I will use about a quart of water for a 2 hour run.  I have a valve that controls the amount of water used so you can up the air pressure to blow the chips and still only use a small amount of water.
When I am done I dry the machine with towels and then go over with an oily rag.
I live in Florida and rust is a constant battle.
Thanks

Ray


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## brino (Dec 7, 2016)

wrat said:


> Truth be told, my motors probably out-gas more than my cutting does.



You mean the machines motors.......right? 
-brino


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## FOMOGO (Dec 7, 2016)

I set up a cold air gun on my mill, and I I have to agree with RJ. It does work as chip removal, but at cooling it is marginal. I have a flood coolant system on my big lathe which I can see the advantages of in a commercial operation, but haven't had a chance to use it. I'm thinking a mister, as mentioned above would be a good compromise. Wondering out loud whether some materials cut better under higher temps than others? perhaps they provide a certain amount of lubricity via there molecular  makeup? Mike


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