Grinding Post HT and kool mist system

I run mine on a 3 HP compressor with a fairly large tank and it cycles pretty often. That may be because I don't have a separate regulator on the mister and it runs at around 100 psi, but I have doubts about running it off a small compressor.

A few years ago, I bought a small compressor (maybe 6 gallon tank or so) for nail guns and such to replace a small pancake compressor. I love the new one, it is unbelievably quiet. It's a California Air Tool compressor and I think it was around $140 or so.
 
Hubert S. said:
i, but I have doubts about running it off a small compressor.
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Well .... I guess I can try it, and return the smaller compressor if it just does not work. I dont really have any concerns about it cycling fairly often, as long as it can keep up. With my dust collection I have more than enough noise in that space anyway....
 
Cushing H. said:
Well .... I guess I can try it, and return the smaller compressor if it just does not work. I dont really have any concerns about it cycling fairly often, as long as it can keep up. With my dust collection I have more than enough noise in that space anyway....
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I am curious how well a small compressor will work. If I get a chance this weekend, I will do a test with my system at lower pressures to see if it is worth putting in a regulator.

The noise does not really matter around the grinder, I wear hearing protection anyway. For woodworking or carpentry, the quiet compressor is really nice though. I remember when I first got the thing, I thought it was broken because it did not make any noise...
 
Put the compressor in another room or outside in a small dog house type shed. Pipe the air inside.
 
Cushing H. said:
What about your dust collectors / shop vacs?
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Same thing for the dust collector....outside. I have a single bag dust collector....might have to trade up to a double bagger. I will get a smaller shop vac and use it for wet stuff and small things. Will repurpose the big shop vac I have.
 
Randydb said:
Same thing for the dust collector....outside. I have a single bag dust collector....might have to trade up to a double bagger. I will get a smaller shop vac and use it for wet stuff and small things. Will repurpose the big shop vac I have.
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I wish. I just dont have that option. for me, it is earplugs....
 
Here is an update as I have tried to get that "cheapo" koolmist system running.

that 1/3 HP compressor from HF is definitely NOT going to cut it. A few random thoughts/observations:
  • I had the water supply bottle just something like 7 inches below the output nozzle on the mister. Anything below 80 psi was NOT sufficient to prime inflow tube. 80 psi did it, but pretty much drained the compressor tank getting the line primed. After that, things ran "ok", even dialing back the airflow (trying to allow the compressor to recover), but it you loose the prime on the liquid line - forget it.
  • things are MUCH easier if you have the water supply bottle ABOVE the mist nozzle. priming is a breeze, and you can dial the airflow back WAY down and still continue to get a mist. However, if you turn off the airflow, you continue to get water flow through the mist nozzle (due to the siphon effect from the higher bottle to the lower nozzle.). Dealing with this in practice would be a PITA.
  • the nozzle screw control on this inexpensive mister is REALLY sensitive to where it is set. screwed too far in and you get no water flow. too far out and you get .... no water flow (i.e. not really the best design of a venturi). the difference between the two extremes is REALLY small. What I do not know is whether the real-thing-KoolMist is any better???????
  • The people who make this (I will not name here), as well as the advertised buy-with fittings (like press fittings for air hose....) do NOT use reasonable quality teflon tape (if that is even what they use ... as I could not pry it out of the threads of the fittings they had put it on). Every single fitting leaked like a sieve (but did fine after I unscrewed them and applied new teflon tape).
Oh Well, I really did need a new compressor for the garage for airing up the car tires (seriously). Here in MN, for several years before I bought my ultra-cheapo Home Depot mini compressor, when it got REALLY cold (like -20 - -30F), that is exactly when the tires would throw a "low presure" warning. That is ALSO the time when every-single-gas-station would mark their tire-inflation stations as "out of order" due to icing up due to ..... wait for it ..... the extreme cold. that little thing I am keeping warm in my garage is **painful** to use. this new 1/3 HP compressor will be a great improvement :-)

Unknowns:

  • will the nozzle control on the KoolMist be any better than on this el-cheapo???
  • Just what size compressor will really work????
I think I need to try to contact KoolMist customer service tomorrow........

Oh well .... someone on the forum recently wrote that part of the "fun" of this is trying things, and failing, and continuing until you succeed. That actually has long been my philosophy to trying new things .... as witnessed by the above :-)
 
I have a couple of the cheap units and they work well. They both draw from a bucket on the floor and the fluid in the line does not drain back into the bucket. I have not used the one on the milling machine for several weeks and it is still primed. I can adjust from a bare mist to a stream of water and the water control does not seem to be overly sensitive. The air control adjustment is more finicky and I mostly run it wide open. Maybe you got a faulty unit?

I cannot tell you the minimum spec for a compressor, but I run mine off a compressor with a 60 gallon tank and a 3 or 5HP motor, not quite sure. I have not timed how often the compressor cycles and I don't always hear it because it is in a different room and I wear ear plugs while grinding, but I would guess the cycle time is around ten minutes or so. You can probably get away with a lot less air. I keep meaning to put a regulator on the line, but haven't got around to it since it works well enough...
 
Hubert S. said:
I have a couple of the cheap units and they work well. They both draw from a bucket on the floor and the fluid in the line does not drain back into the bucket. I have not used the one on the milling machine for several weeks and it is still primed. I can adjust from a bare mist to a stream of water and the water control does not seem to be overly sensitive. The air control adjustment is more finicky and I mostly run it wide open. Maybe you got a faulty unit?

I cannot tell you the minimum spec for a compressor, but I run mine off a compressor with a 60 gallon tank and a 3 or 5HP motor, not quite sure. I have not timed how often the compressor cycles and I don't always hear it because it is in a different room and I wear ear plugs while grinding, but I would guess the cycle time is around ten minutes or so. You can probably get away with a lot less air. I keep meaning to put a regulator on the line, but haven't got around to it since it works well enough...
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Well this one I got is 1 gal, and it emptied in no time. I need to set mi sights higher clearly...

I’m surprised. How does a unit like this even begin to fill a car tire???
 
Cushing H. said:
Well this one I got is 1 gal, and it emptied in no time. I need to set mi sights higher clearly...

I’m surprised. How does a unit like this even begin to fill a car tire???
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I have a little 1 gal compressor that will run a brad nailer somewhat ok (it came for "free" with the nail gun as a promo), but it cycles after shooting three or four 15ga nails. I still use it sometimes because it is light and portable, but it struggles even with bicycle tires. The noise just isn't worth it and a hand pump is just as quick...

If you don't want to get a big compressor to run a mister, maybe you can run a drip system for cooling. When I first tried the mister for grinding, I essentially used it like that and added a lot of water instead of just a mist. It makes a bit of a mess, but works well to prevent burning the edge. There are quite a few posts on the forums about different methods ranging from gravity feed to aquarium pumps to just throwing water at the belt by hand...
 
My single unit kool mist does require higher psi (like 80) to operate. My dual noga units (made in Israel) only take about 30 psi to run well and they are amazing. The quality is superb.
 
Hubert S. said:
If you don't want to get a big compressor to run a mister, maybe you can run a drip system for cooling. When I first tried the mister for grinding, I essentially used it like that and added a lot of water instead of just a mist. It makes a bit of a mess, but works well to prevent burning the edge. There are quite a few posts on the forums about different methods ranging from gravity feed to aquarium pumps to just throwing water at the belt by hand...
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I have been spraying the belt with a hand spray bottle ... but it just does not last long...
 
I just got off an extremely frustrating call with the KoolMist folks - speaking with the person who answered phone and said they were "in sales" .... but said they had NO engineering folks to speak to .... and apparently did not understand the difference between psi supplied by the compressor (which they called a "generator") and the HP of the motor for the compressor (i.e. the ability of the thing to supply a given pressure at a given flow rate) .... they would ONLY talk about pressure (meaningless when the tank empties), and absolutely refused to try to go anywhere near the question of "how powerful" the compresor should be, and kept saying .... go the people who sell the "generators" and they will tell you what to get (but without giving me enough information about the mister to try to size anything). Oh .... they also could not get the difference between the compressor physically shutting off versus having the tank pressure drop to zero....

After getting cut off, and calling back, I FINALLY got this little tidbit out of them: They test/expect their nozzles to operate in the range of 80-120 psi, and they **expect** a flowrate of "about 1cfm" at those pressures.

so .... that should be enough to size a compressor to meet their demands of this sprayer.

for example, this one from HF should work (4 cfm at 90 psi)?
https://www.harborfreight.com/air-t...i-oil-free-portable-air-compressor-64294.html

or this one at 4 cfm at 90 psi? :
https://www.harborfreight.com/air-t...hp-150-psi-oil-free-air-compressor-69666.html
 
I’d go with the highest cam and gallonage you can find. I have a Porter Cable 6 gallon pancake that puts out • Air Delivery @ 40 PSI 3.5 SCFM
• Air Delivery @ 90 PSI 2.6 SCFM.

It runs all the time at the lowest pressure while using the Kool Mist unit.
I’m trying to figure out if an electric pump will actually work with the Kool Mist set up and not use the compressor. Maybe just plumb the pump into the liquid side of the unit.
Scott
 
I suspect the pump idea will kind of work .... you will get a stream of liquid out the nozzle, not a mist .... so you might not really cover the entire surface of the belt?
 
SS369 said:
I’d go with the highest cam and gallonage you can find. I have a Porter Cable 6 gallon pancake that puts out • Air Delivery @ 40 PSI 3.5 SCFM
• Air Delivery @ 90 PSI 2.6 SCFM.
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Hi Scott. I would think the "runs continuously" thing is more related to HP of the motor than tank size (and will presumably show up in cfm/min vs psi. the two units I cited have something like 4cfm at 90, so maybe would be somewhat better than your experience ..... though thank you very much for the benchmark ..... I will keep that in mind as I look at compressors.
 
You want a good amount of air to atomize the water into a cooling mist. Otherwise, it is just a drip system.
 
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