Home built fogless mister

[Terry S]

Here's a brief summary with pics of a fogless mister I have been designing and building.
I built this for use on my BP mill. I don't do enough heavy work to justify the maintenance of a flood system - and my old-timer "Mystic Mister" tends to fog up my basement shop in no time. At the recommendation of another member, Terrywerm, I looked into the design/build of a fogless design. The system I built uses a 20 oz Coke bottle for a fluid reservoir, and has two regulators: one for air against the nozzle and one for air pressure on top of the fluid reservoir. I have about 10 hours on the system now, and am quite satisfied once I have learned how to "tune" it. It makes no fog whatsoever.

The mixer assembly is made from a single piece of soft brass square stock.
   
The air enters the lower tap and passes straight through into the mixing tube. The fluid enters the upper tap and is regulated via the needle valve. The fluid and the air mix in a "low velocity" chamber under the needle valve to prevent further "atomization" of the fluid. The needle valve seat orifice is .040 in. I find that in normal use, the needle valve is about 1/4 turn open with 10 psi air pressure in the reservoir.
Here's a view of the disassembled mixer valve showing the needle stem, the packing gland and the captive O ring.
   
Here's a detail showing the packing gland with the captive O ring slot. The O ring is an 1/4 x 1/8 standard size. It is slightly compressed on the OD in the gland. The gland compresses the O ring in the "Z" direction until the gland bottoms out. This squeezes the O ring against the needle stem making a water tight sea. Cutting fluid is not exposed to the needle threads or the packing gland threads.
   
Here's a view of the "Control Panel." I have it mounted on the right hand side of the mill for east of adjustment when running. The right column is for air and the left column is for fluid. The "toggle" valves on the top of each column start and stop the flow with a flick of a finger.
   
Here's a view of the back of the control panel. The Coke bottle, regulators, etc. are mostly shielded from flying chips by the panel.
   
Here's a view of the mixer installed on the mill. I like to position the mixer so that the needle valve knob is easy to reach during operation.
   
Some notes:
1) I need to do some more work on the Tinker Toy mount for the mixer head. Right now I have to use an Allen wrench to adjust it. I may look at retrofitting one of those multi-flex dial indicator holders. I find that fine tuning the position of the air blast can make quite a difference on the efficiency of chip clearing. When taking a heavy side cut, the mill runs noticeably quieter when the chips are being cleared and re-cutting greatly reduced.
2) There is absolutely no fog generated, but I find that I often have to "restart" the fluid flow by opening and then re-adjusting the needle valve after I have stopped the fluid flow. Plus, I like to start the cut with a little extra splash of fluid on the cutter before settling down the the mist feed. I may look at adding a by-pass valve to the needle valve to get this function. I find that the proper flow of fluid generates a sound like "bacon frying" when operating (you have to listen carefully to hear it). If I cannot hear the bacon sound, I tweak the valve open and then closed to get the fluid flowing.
3) The final mixing nozzle at the end of the mixing tube has a .040" bore (#60 is smallest drill bit that I own). When you do the math, this bore regulates the air flow at about 0.3 scfm with 5 psi of air against the nozzle. The air flow is audible, but not loud. The nozzle velocity at this setting does a good job of clearing chips from the cutter as long as the nozzle is within about 3/4 inch of the cutter.
4) After about 4 hours of cutting steel on a project, I still haven't used up 20 oz of fluid. I have been using the standard dilution of "Cool Mist."

Terry S

[EdK]

Terry,

Wow! Most impressive project. How much air is required to use it? What size is your compressor?

Thanks,
Ed

[Terry S]

(12-31-2013, 01:22 PM)EdK Wrote: Terry,

Wow! Most impressive project. How much air is required to use it? What size is your compressor?

Thanks,
Ed

The nozzle consumes about 0.3 scfm of air (by calculation). I am running a 3/4 HP "Ultra Quiet" compressor from California Air Tools. The compressor is rated about 1 cfm and cycles 2 or 3 times a minute, so I tend to believe the 0.3 scfm calculation.

By the way, if anyone is looking for a smaller, quiet, not-too-high-cost compressor, I recommend checking out California Air Tools. "Ultra Quiet" may be a stretch, but two people can have a conversation right on top of it without having to use raised voices. My bench grinder makes more noise. Home Depot is a retailer for California Air Tools, but you have to order it over their website and have it shipped. I think I paid around $170 including MN sales tax.
Terry S.

[terrywerm]

Looks great, Terry. I am still working on the drawings for mine, should finish today or maybe next weekend and will post them when complete.

Not to hijack this thread, but I have a similar (if not the same model) compressor as Terry S, and I love it for in the basement shop. I did add another 5 gallon air tank to it though, increasing capacity from 1.6 gallons up to about 7. Run time is longer, but it does not kick in nearly as often.

[EdK]

(01-01-2014, 11:39 AM)terrywerm Wrote: ...

Not to hijack this thread, but I have a similar (if not the same model) compressor as Terry S, and I love it for in the basement shop. I did add another 5 gallon air tank to it though, increasing capacity from 1.6 gallons up to about 7. Run time is longer, but it does not kick in nearly as often.

That's good to know since I've been looking for a small compressor for the basement to use until/if I get a large one that will be located in the garage and air piped into the shop in the basement.

Are those compressors you guys have oil-less? I'm not fond of oil-less compressors since they tend to run hot and don't last as long. I had one some years ago and gave it to my nephew.

Thanks,
Ed

[terrywerm]

Ed, yes they are oil-less. I have the model 1675A which is 3/4 HP, with a 1.6 Gal aluminum tank, it weighs 35 lbs and is extremely portable. They are very quiet, only 58 dB. They are available in several sizes, starting at 1/2 HP, but the bigger they are, the louder they are, though not significantly. Their web site is here: http://www.californiaairtools.com/

I was originally going to build a quiet compressor from an old freezer compressor for my basement shop. They are very quiet but are also very s-l-o-w. Terry S told me about these and I was sold. Be sure to check out their sound level comparison video.

Terry S got his through Home Depot, I bought mine a tad bit cheaper as a scratch and dent special direct from California Air Tools in their Ebay store. $160 delivered to my door, no sales tax or shipping. It arrived with a couple of small scratches in the paint on one end of the tank. No big deal since it's going to sit on the floor under the bench anyway! So far I am thrilled with it!

I do have a large 6 HP compressor out in the garage, but it rattles the whole house when it lights off. Wife about jumps out of her skin, too! I don't need that giant running all the time for the tiny bit of air I will need in my basement shop.

[Terry S]

Quote:Are those compressors you guys have oil-less? I'm not fond of oil-less compressors since they tend to run hot and don't last as long. I had one some years ago and gave it to my nephew.

Thanks,
Ed

Yup, these are oil-free design, rocker pistons with Teflon rings and coated thin-wall aluminum cylinders. You are right in that oil-free compressors have a limited life. The mfr claims an operating life of 3000 hours minimum before a rebuild is required (we'll see). California Air Tools has designed in the ability to replace the cylinder sleeves and the pistons when a re-build is required. For my use, 3000 hrs is a long time. The mfr may or may not be around when the time comes. Even if they still exist, it will be interesting to see the cost of rebuild parts versus the cost of simply buying a new compressor.

For small, home use, compressed air systems, my personal preference is for oil-free. I only add oil where it is needed with a small pneumatic "oiler." I have an oiler on the power draw-bar on the BP mill. Everything else runs without oil. Keeps the plumbing clean, and eliminates blowing an oil mist from blo-guns. Water is another issue. I make no attempt to dry the air. For what I do, dry air is not required, and the condensation in the pressure tank usually catches enough of the water so as not to be a problem. (If only I could remember to drain the tank on a regular basis - especially in the summer). The compressor I bought has an aluminum tank - supposed to keep the compressor light for portable use, but I bought it because it reduces the corrosion hazard present with steel tanks.
Terry S.

[Micktoon]

Nice job there Terry , How do people find these systems work , sort of pro's and con's , there seems to have been a few mentioned about the forums latley.
Thanks for posting , Cheers Mick.

[Terry S]

(01-01-2014, 03:02 PM)Micktoon Wrote: Nice job there Terry , How do people find these systems work , sort of pro's and con's , there seems to have been a few mentioned about the forums latley.
Thanks for posting , Cheers Mick.

So far, I have been very happy. There is no fog what-so-ever, whereas the old Mistic Mister I have fogs up the shop in no time.

As far as cooling, I am impressed. I was doing some end milling on a piece of 1/4 inch mild steel, taking about .040 DOC passes at about 6 in/min. I had to make several passes to level out a jagged edge. I was using an HSS end mill. I set up the mister to keep a tiny (just receptacle) puddle of coolant running ahead of the cutter. At the end of each pass I checked the work piece by touching it. I was surprised that the work piece felt cooler to the touch than vice it which it was clamped. As an experiment, increased the feed rate and cutter speed until blue chips were being thrown (I know because a couple landed on my hand and branded little smiles). After this pass I stopped the mill to check temps. The cutter was cool to the touch and the work piece was still cooler than the vice. I have been using "Cool Mist" at the normal dilution. About 4 hours of milling consumed less than 6 oz of fluid. The work comes out mostly dry, but there is a slight oily slime left on the vice from the lubricant in the Cool Mist. Apparently, the chips come out so fast that they are not cooled, while the cutter and the work place remain under the mist application and a gentle air blast which evaporates the water and helps to clear chips from the cutter. There are commercial versions on the market that actually use a small metering pump to meter the fluid into the mister, but these are fairly expensive, and intended for the professional shop. There is also one commercial version on the market that uses compressed air and a metering valve similar to what I have built, if you don't want to go the home-made path.
http://www.tormach.com/store/index.php?a...&ref=32682#

If you do a search on "fog less mister" you will get several versions of home built misters, some with YouTube vids showing operation and construction.
Terry S.

[EdK]

Terry's,

I assume those compressors are made in China, correct?

I may have to go take a look at them. They would probably work just fine in my basement shop situation.

Ed