Official Luthiers Forum!

I've been searching the archives quite a bit to find any info on spraying
finish that I can. It appears that many of you like and use the Sata
MiniJet. Right now I'm brushing on Behlen's Rockhard Varnish, and I'd
like the first half of the next year to be a time of setting myself up for
spraying. I'm looking at one of the Turbinaire HVLP systems because of
small space requirements, low volume, and dry air. I'm just not sure how
the gun compares to the Sata, DeVilbiss, and Binks guns many of you
mentioned in previous threads. A MiniJet or similar class of gun along
with a compressor might carry a similar price tag as the Turbinaire.

What do you look for in a compressor for spraying? Where do you set the
PSI when you spray? How gallons should it be able to store without
cycling on over and over?

Thanks for any help on this one. It's a completely new area to me.

Two Pistons and a capacitor start electric motor.

Not sure of the gallons. Mine is a two lung compressor and is big enough it is horizontal tanked and two capacitors on the motor for starting, 120V unit. Rolls around on two wheels which are on one end.

I'd caution you against diaphragm type units, they are horribly noisy. The kind carpenters use to run nail guns.

I use between 20 and 30 Lbs pressure for spraying Nitro Lacquer.

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http://www.dickeyguitars.com

Depends what you want to do with it James.  Spraying doesn't take much volume, but if you want to power a sander, you will need a lot more capacity (10cfm and 100 to 120 psi).

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A higher purpose for wood.
Rich Smith
Issaquah, WA

James

Allen MacFarlen has done a brilliant tutorial on spraying and spray guns here and it's what he does as a fulltime job so there's some terrific info there.

Spraying and Spray Guns

Cheers

Bob

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Bob Connor
Geelong, Australia

The compressor you get will have to be able to supply the gun you are looking at.  I'm going to make a HUGE ASSUMPTION here that since you don't have a spray booth with equipment for spraying solvent-based products you will be spraying water-based products. 

When you look at the guns, you will see that they take a certain amount of air flow - CFM - to run them.  For a conversion Gravity HVLP it'll run in a range from 7 to 12 or even 15 CFM.  That's more air output than the typical low-end big box store compressor puts out before it has to cycle on again. 

If all you are spraying is guitars, that may be OK, but I'd recommend a larger, two stage compressor, 5 hp or better.  Look at the air flow they put out at 30/60/90/120 psi.  Most of the time, you will have a regulator on your gun, so the compressor will put out 50-80 psi from its outlet and your gun will regulat it back down to between 18-28, depending on the product you are spraying, and the type of gun you are using...

Mitch

    There is alot of good info here. In a short shot you can look at 2 systems , the turbine and the compressor. With turbine systems , they are using a turbine to create volume without alot of pressure. This is a decent system and often not as expensive.
    The compressor is a base machine that can power more than the paint gun. You also are looking at pressure cups or HVLP ( Hi Volume Low Pressure ) Also with the compressor you neeed a water separator on line to avoid water contamination.
    I use both and your result will be in relation to the
preping and quality of the gun you pick.
   So much to learn as finishing is as much a process as is building
john hall

I have a Craftsman 4HP compressor that is about 12 years old. It has been very reliable. At the time I purchased it I wanted to get something that had a decent CFM rating so I would have air when needed but that didn't cost and arm and a leg. It has been good compressor but since it draws 15amp on start up it is right on the edge for standard 120V circuit. Depending where I plug it in I will have to reset the breaker in my main breaker panel. If you decided you are going to get a bigger compressor (which I would recommend since it is a great tool that you will have from some time), be aware that you may need to run 220V to get the amps under control. Depending on your shop electrical set up this may not be a big deal.

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Brad
Avon, OH

Most of what I'd say has been covered already, so I'l just add my .02. I look
for maximum cfm and quiet operation.
I currently have a 5hp 4 cyl 60 gal 18 cfm unit made by Quincy that I like
very much.
http://www.quincycompressor.com/air_master.html
I also added on an additional 60 gal tank (bought used from my local
compressor store for $75) to increase the storage capacity for when I'm
running heavy drawing tools such as sanders.
-C

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Freeborn Guitars
and home of BeauGuard©

Pretty much any medium-sized compressor (I have a cheap, nasty, oilless 1.5HP one with a fair-sized tank) will be enough for the MiniJet.

Thanks, everyone. Especially for the tutorial link. This all gives me good
info to go on.

James-
Don't forget to put aside a bit of the budget for water/oil traps, filters, etc as well as piping, manifolds, and connectors- it can easily add up.
I had some trouble with blushing (spraying nitro with a Walcom STM HVLP gun) until I put a dessicator into the line for the spray gun. BTW, silica gel dessicant can be re-used- just put it in a low oven for an hour or two.

If you have the cash, space, and the capability of wiring it, a larger compressor is the way to go. If you don't, a 4cfm@90psi compressor will do in the interim. You won't be able to use pneumatic sanders, etc, but you'll be able to spray, and blow dust. Another thing to check is the cfm air requirement for a 'vacuum venturi', if you want to play with vacuum and don't plan on buying a vacuum pump.
Cheers
John

My understanding is that the nicer HVLP guns atomize the finish
extremely well and lay down a fine coat that doesn't need much work to
level. Do the Turbinaire guns lay down a fine coat?    

General advice: do not go oilless; get a bigger machine than you think you need--you may want to run tools later on, and there are significant pressure losses in the line--the machines are rated right at the output of the machine.

Ignore horsepower, the numbers aren't real. CFM at a given pressure is the significant number.

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Howard Klepper
http://www.klepperguitars.com

When all else fails, clean the shop.

James...

Do a google search for "Duty Cycle" and read up on it as it pertains to mechanical systems. Look for the Duty Cycle data for any compressor/motor you are considering along with the "Mean Life" of the compressor.
That data, along with CFM/Pressure data will give you a good idea of the robustness of the unit. As mentioned earlier, disregard horsepower numbers...they are generally not indivcative of what the unit uses/needs during normal operation.
Do follow the maintenance schedule for intake filter and oil changes. In my shop, with the level of usage mine gets, I do this every first of the year.

And...buy bigger than you think/avoid oilless models.
If you buy a stand up model, be sure to get some earthquake strapping for it. Plumbing stores have nice sets for water heaters that will work for the compressor and try to locate it in a corner, if possible, for added rigidity/security.

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Hank Mauel

    You do want to see at least 2 cylinders on a piston compressor. CFM and Pres is the best gauge. One companies 3hp is another 2hp.
    I have a 20 cu ft at 120 psi. Get the best you can afford. Price isn't the best gauge as there are plenty good medium range units out there.

This is all very helpful. It looks like I'll look for capacity and CFM,
preferably a non-oilless. Thanks too for the google idea, Hank.

Oh, the usual....

Great personality. Healthy, fit body. Good investment value (i.e, wealthy
parents).