Spray Gun CFM

[Willyou]

I have a 20 gal. compressor that has an output of 6.4 cfm. I am contemplating purchasing a spray gun that specs say consumes 7.9 cfm. I assume that is max.
I understand that it is not 100% necessary to have a compressor cfm output exactly match the consumption of a spray gun. If the compressor can't quite keep up, it is easy to pause a bit to let it catch up. Also, one is not usually running the spray gun continuously. For those more experienced, as a practical matter, how close to a match should they be? What difference does 1 or 2 cfm make when stopping and starting frequently as when working on a piece of furniture and especially when your gun settings are less than wide open.

[jteneyck]

I have a 20 gal. compressor that has an output of 6.4 cfm. I am contemplating purchasing a spray gun that specs say consumes 7.9 cfm. I assume that is max.
I understand that it is not 100% necessary to have a compressor cfm output exactly match the consumption of a spray gun. If the compressor can't quite keep up, it is easy to pause a bit to let it catch up. Also, one is not usually running the spray gun continuously. For those more experienced, as a practical matter, how close to a match should they be? What difference does 1 or 2 cfm make when stopping and starting frequently as when working on a piece of furniture and especially when your gun settings are less than wide open.

I assume the 6.4 cfm rating of your compressor is at 90 psi, correct?  The 7.9 cfm requirement of the gun is at some lower pressure, for sure, maybe 45 psi.  For most things I spray I use 29 psi at the inlet to the gun, and that includes when I've used the purple HF gun which is rated at higher inlet pressure.  So, your compressor will likely work just fine although it will run non-stop after you empty enough out of the receiver to trigger the pressure valve until you pause long enough for it to catch up.  


I think you will be fine.  However, if you do much spraying your compressor is going to wear out a lot faster than it would just filling tires, etc.  Drain the regulator bowl and tank after each spray session, too, to keep water out of the line.  

John

[Willyou]

No. Sorry. I should have said: 6.4 @ 40, 5.3 @ 90. My spraying is infrequent and I mostly do furniture where I'm not continuously on the trigger. Yes. I do drain it after every use and have a water separator and filter on it. Compressor is a California Air 10020c. Nice unit.

[jteneyck]

No. Sorry. I should have said: 6.4 @ 40, 5.3 @ 90. My spraying is infrequent and I mostly do furniture where I'm not continuously on the trigger. Yes. I do drain it after every use and have a water separator and filter on it. Compressor is a California Air 10020c. Nice unit.

You will still be fine unless you want to spray non stop at greater than around 40 psi, or the gun requires that kind of pressure to spray well.  That said, it would be better to get a LVLP gun so the required cfm is lower than the rated output of your compressor.  

John

[Willyou]

You will still be fine unless you want to spray non stop at greater than around 40 psi, or the gun requires that kind of pressure to spray well.  That said, it would be better to get a LVLP gun so the required cfm is lower than the rated output of your compressor.  

John

Yeh. I haven't been able to find an LVLP of reasonably good quality with a side mounted cup.

[jteneyck]

Yeh. I haven't been able to find an LVLP of reasonably good quality with a side mounted cup.

Why a side mounted cup?

John

[Willyou]

Generally, they tend to be smaller and, I think, the smaller gun is easier and better to use when spraying furniture items. I just finished a restored glass front book case using a mini-gun with 1.0 mm tip. It worked fine inside and out and I feel like I have better control with the smaller spray pattern. The swiveling side cup lets me spray the underside of the top and straight down on the upper surfaces without spilling.
I would like to get a similar gun that will accommodate larger tips and thicker materials . I have looked at the PPS system but, the whole system just looks too big for my purposes. I have used my $10 HF gun some and it is like driving a race car to the grocery store. The Sprayit 352 is a cheap gun that comes with a 1.4 and a 1.8 tip and has the side cup. Reviews are mixed but, for the price, I can experiment. The next step up appears to be a knock-off Iwata W-101 in the $50 - $70 range from China. I have come close to ordering one but, not yet.

[jteneyck]

Generally, they tend to be smaller and, I think, the smaller gun is easier and better to use when spraying furniture items. I just finished a restored glass front book case using a mini-gun with 1.0 mm tip. It worked fine inside and out and I feel like I have better control with the smaller spray pattern. The swiveling side cup lets me spray the underside of the top and straight down on the upper surfaces without spilling.
I would like to get a similar gun that will accommodate larger tips and thicker materials . I have looked at the PPS system but, the whole system just looks too big for my purposes. I have used my $10 HF gun some and it is like driving a race car to the grocery store. The Sprayit 352 is a cheap gun that comes with a 1.4 and a 1.8 tip and has the side cup. Reviews are mixed but, for the price, I can experiment. The next step up appears to be a knock-off Iwata W-101 in the $50 - $70 range from China. I have come close to ordering one but, not yet.

For occasional use nearly any gun will work if the specs. fit your needs.  If you spray regularly though better quality guns generally are easier to use and last longer before the seals give out.  I spray furniture and have minimal problems with a mid sized gun with a bottom mount PPS cup.  The PPS system allows you to spray at any angle and that allows me to get into most places.  If I sprayed gallons of stuff I'd put a pressure pot on the gun I have and that would let me get into even tighter spots.  The side mount guns are fine for detail work, but too small IMO for furniture and cabinets.  

But if you want an Iwata mini gun but don't want to spend more than $70 why not buy an Iwata. $70 Iwata 101

John

[Willyou]

Yes. That is one of the guns I've been looking at. The W-101 151g that consumes 5.1 cfm matches the output of my compressor but, I haven't found one yet among the Knock-offs. I saw one on Ebay a week ago but missed it. The 101 152g jumps up to 7.9 cfm. That's what prompted my OP. Maybe it's not enough difference to be concerning. I'm in no hurry. I may just keep watching for another one for a while.

[Willyou]

Follow-up:
While continuing my search and research, I decided to purchase the Sprayit from Nome Depot for $15. For the money, I could throw it away and not be out much. Also, I thought, Home Depot would take it back if not usable. I was disappointed that it came with only a 1.5 tip rather than the 1.4 and 1.8 tips as advertised. Oh well. The main point is that it works great! Keep in mind that I have no experience with the "good quality" guns. So. I can only judge what I see and the results I get. I see smoothly finished aluminum castings and the use of well machined brass and stainless in the working parts. After giving it a good cleaning, I hooked it up and loaded it with some water based poly (Varathane from Home Depot) unthinned straight from the can and sprayed some stuff. After 3 coats with light sanding between coats, the finish was as smooth as glass. I am impressed. The specs say that it requires a minimum 4 cfm. So, my 6.4 cfm compressor has no trouble keeping up. I was able to turn the pressure down to 20 psi and get a fine gentle spray that allowed me to move slowly and methodically in intricate areas. Or, I can turn it up if working on broad areas where I can work faster. For me, it is just about perfect.

As I found the Sprayit to be a success, I thought I would like to have a larger needle and nozzle for spraying acrylic paint. I couldn't find any other tips available for the Sprayit. But, I noted that there is a big "W-71" embossed on the side of the gun that I had not really paid any attention to before. When doing a search for "W-71", I found a lot of the same gun at a variety of prices including one with the Iwata brand name (higher priced. Of course). So. I'm assuming that the Sprayit and the other no name W-71s are Iwata knock-offs. I found that I could buy several different sizes of needle, nozzel, cap, and packing from sources in China. With fingers crossed, I ordered a 2.0mm for $14 including shipping. In about 2 weeks, it arrived and it works perfectly.

On a cool day in the 60s, I pulled some left over latex paint off the shelf to give the 2.0 tip a try. Because the paint had been on the shelf for quite a while and the temp was cool, it was pretty thick. Using my Ford #4, I got the viscosity down to about 2 min before it would flow through the gun well. Setting the pressure at about 25-30 psi, I laid down 3 coats and the result was even and smooth as glass. I'm impressed. When the weather warms up, I'll get some fresh paint and see how much thinning is actually required to get the same results.

My only issue with this gun is that, initially, the fluid tip was very difficult to loosen. I ended up removing all of the soft parts like the needle packing, etc, and heating the nose of the aluminum casting as much as I could with an electric heat gun while applying pressure on the nozzle with the wrench that comes with it. It finally broke loose. I guess some kind of sealant was used at the factory that "glued" it in.

I would recommend that anyone with a small compressor who wants to do some spraying give these guns a try. If your don't want to go with a "cheap" gun, then the Iwata W-71 would be a good choice. The Iwata W-101 is a newer model of the same gun but, be careful as it comes in different configurations, some of which require higher cfms. BTW, you can find more than one dealer on Ebay that sells the no name W-71s for around $20 with your choice of tip size. So, you can buy a whole set to meet all your needs and still not have $100 invested. You can also find the Iwata W-71s there.