Air compressor for woodworking shop?

[estesbubba]

I'm going to keep my current HF air compressor in my garage for tires, etc. and buy a new one for my woodworking shop. This air compressor will only be used for woodworking and no cars, etc. will ever be in the shop. I have a Fuji 4-stage HVLP and initially won't use the air compressor for spraying but you never know down the road. So I would like a compressor that could spray later on if needed.

 

So, any suggestions on what to get? SCFM, HP, tank capacity, etc.?

[Boatworks Today]

If you'll be spraying you'll need to have a minimum of 3hp, 60 gal tank and a pump that can output at least 16 cfm.  More would be better, but this will work for most guns

 

Edit:  Chet brought up a good point.  Compressors of this size will require 220v..

[ChetlovesMer]

Do you have 220 VAC available or are you only looking at 115 VAC?
Reason I ask is that it seems round here Craigslist has tons of 220 air compressors.

[dwacker]

It would be to hard to say what you will need in the future. Worse case you might be spraying with a conventional hvlp gun. That would need an 80G two stage 5hp compressor and even at that you would be abusing the compressor. Personally I would not even worry about spraying with the compressor at all and just count on the fact that you have a turbine sprayer. A small quality contractor compressor is more than enough for most folks. They will power all your nailers and staple guns just fine. If you are thinking of going with air sanders you will need a hell of a big compressor or rotary screw. But again I would just count on the fact that you will probably never need air sanders.

[Vyrolan]

Sorry to come in with a semi-hijack, but relevant with some of the responses...what would you recommend for a non-spraying compressor?  I don't have anything air-powered but would like to get a basic setup for doing brads/pins/staples that isn't too expensive or bulky.  I'm not big on fasteners so it wouldn't see extensive use outside of making quick jigs, shop furniture, and other small miscellany.

[estesbubba]

I ran both 240 and 120 to the location so that is not a problem. Like PB said, since I have a nice turbine I will probably never spray with the compressor - more equipment to buy and another learning curve. I also don't see myself using air sanders so maybe I'm looking at a 120V small compressor. 

[Boatworks Today]

Sorry to come in with a semi-hijack, but relevant with some of the responses...what would you recommend for a non-spraying compressor?  I don't have anything air-powered but would like to get a basic setup for doing brads/pins/staples that isn't too expensive or bulky.  I'm not big on fasteners so it wouldn't see extensive use outside of making quick jigs, shop furniture, and other small miscellany.

 

Just a basic pancake compressor is all you need for nail / staple guns. 

[minorhero]

I spray all the time with a hvlp spray gun using a 2hp 20 gallon compressor. The compressor kicks on when spraying but is able to keep up for purposes of spraying. Its not the literal ideal, but I have not noticed a deficit when either spraying paint or when spraying finish.

 

I should note that I do not hold down the spray trigger for 60 seconds straight. I am sure my compressor would have trouble with that. But when doing spray bursts I am only trying to get an even coat the length of one side of the piece before stopping that stroke. This is more then enough for me.

[rodger.]

I have a small dewalt trim compressor - and I mean small (1 gallon). I use it for nailers (16, 18, 23). Works great! It is also small enough to bring in the house for trim work and home Reno's. Fantastic unit. I have never run out of air using it.

http://www.dewalt.com/tools/compressors-hand-carry---electric-d55140.aspx

[mikem]

I have a 6gal pancake compressor, that is about 10 years old.  It works great for nail guns.  I have used it to inflation of car tires and a small inflatable pool when the kids were much younger.  I do use it occasionally to inflate car tires as well.  I have cheated, and used an HVLP sprayer on it for spraying shellac on medium to small projects, with okay results, but wouldn't recommend it unless you are desperate. I wouldn't use it for any other air powered tools, it just doesn't have the capacity.  

[Trip]

It’s all down to the tools you want to drive…

 

One piece of advice: get more compressor than you think you need… It’s what I did, and it’s paid-off over the years. I have my shop, garage and outbuilding plumbed with shop air… It’s been a great investment. As an example, I rebuilt a piece of garden equipment – A die grinder, impact wrench, right-angle grinder, right-angle sander, etc were perfect for the project and saved me hours or toil with electric and/or hand tools… Once you get something like a die grinder, you’ll use it – trust me…

 

BTW: a pancake compressor is a good place to start. Even if you go big later, you may still want to keep the pancake --- I still have mine and use it for trim jobs – it’s perfect for shooting nails…

 

But if you start looking at grinders, go big or go home…

[Dan S]

Regardless of the size you get, try and make sure it's not an oil-less model. Oil-less models are usually louder, weaker, and wear out faster.

This is the model I currently have.

http://www.homedepot.com/catalog/pdfImages/39/39c88b0b-edce-45e8-90d7-2c409ecbc003.pdf

When I purchased it, is was the cheapest oiled compressor I could find, but sadly it looks like it's not being made anymore.

[chefmagnus@grics.net]

I have a DeWalt - D55141 Emglo Compressor that have connected to a tank that I got from Harbor Freight to get added volume of air for doing some painting projects. I have a "T" with a valve on it when I only need one tool but I have a 4 barb quick connect on the big tank. Works well, quiet, and not a lot green.

 

Chef

[dwacker]

Its not a good idea to add second tank to a small compressor. The tank that the compressor comes with is based on the motors duty cycle. Increasing the tank size runs the motor well past max duty cycle. Adding a second tank does not increase CFM which is what is needed for spraying or air tools. 

[Dan S]

Adding a second tank does not increase CFM which is what is needed for spraying or air tools.

What?

More stored air, means you can discharge air at the same cfm for a longer period of time!

[Tpt life]

If it takes longer to charge the system than the duty rating of the motor, then you run the risk of overheating and premature failure. It is a calculated balance to figure system volume. Even shop piping adds volume. Most small compressors have duty ratings in the 20% range.

[dwacker]

What?

More stored air, means you can discharge air at the same cfm for a longer period of time!

 

NO cfm is a function of the pump. Once air pressure drops it drops on both tanks and takes twice as long to regain pressure. Thus abusing the motor. You size your compressor based on the needed CFM. So if your standard HVLP gun needs 15CFM and your compressor can push 18CFM it won't matter if the tank is half empy and motor is running or full you still have 18CFM.

[Dan S]

NO cfm is a function of the pump. Once air pressure drops it drops on both tanks and takes twice as long to regain pressure. Thus abusing the motor. You size your compressor based on the needed CFM. So if your standard HVLP gun needs 15CFM and your compressor can push 18CFM it won't matter if the tank is half empy and motor is running or full you still have 18CFM.

What I was referring to was the fact that when it comes to the pure physics of the problem, you answer is not correct. A larger storage capacity lets you discharge the tank at the same rate for a longer period of time, before the tank has to be recharged. if memory serves, this comes back to a derivative of the ideal gas law.

[chefmagnus@grics.net]

We called DeWalt when we were having trouble with the paint gun. They said that the storage tank on the compressor was too small. They told us what we need to buy. They also told us that the regulator on the compressor was fine for both tanks. As far a over heating the motor it runs less with the large storage tank than when I had the spray gun hooked up the compressor. The tank is 26 gallons and rated for 200 psi. I have put a moisture filter on the system. The highest that I have ever gone is 110 psi while trying to put nails into some cherry molding.

 

Why do I have a extra tank. For awhile I had a roommate that painted cars in the garage. The state outlawed doing this in the home garage so he moved to Texas and now has a 10 bay garage.

 

Chef 

[ponderingturtle]

Its not a good idea to add second tank to a small compressor. The tank that the compressor comes with is based on the motors duty cycle. Increasing the tank size runs the motor well past max duty cycle. Adding a second tank does not increase CFM which is what is needed for spraying or air tools. 

Yes and no.  It depends on the CFM of the motor and the size of the tank.  If you have a 2 horse compressor with an 8 gallon tank adding a 30 gallon pressure tank makes sense and will work fine.  If you add a 30 gallon tank on a tiny craftsman compressor like I got from my parents you will burn out the motor because it will take you a hour to fill the tank.

 

Unless you are using a tool constantly you need surge capacity to run the tool for a while then the you are done and can let the tanks refill.  So it will not solve every issue but it will help in some cases.

[dwacker]

Correct but that is not how you size a compressor nor does it take in to account duty cycle. CFM on a compressor is a function of the pump and motor. Jury rigging a compressor with a larger tank destroys the compressor. The only time you can get away with this is with a true 100% duty cycle compressor.

A small compressor like the Dewalts are going to be low duty cycle at best. This means with the factory tank only they should run at duty cycle at the maximum stated cfm. A standard HVLP paint gun will use 10-15cfm. The Dewalt mentioned has a 2gallon tank @ rated at 2 cfm meaning it will always run in the red with anything that consumes over 2 cfm and that is most likely over stated.

If by means of some magic a tiny compressor could possibly drain out its full capacity without ever dropping pressure over the course of a full minute 28 gallons is only 3.74 CF but we know this is not possible. You need more than double that to spray with a conventional HVLP gun so that cuts it down to about 30 seconds at very most with no pressure drop, again not possible. Reality is you may have 10 seconds of actual trigger time at the needed cfm and pressure. Even if you just spray in short burst you will never catch up.

 

So basically that few seconds of trigger time will seem like a lot of finishing time and you may get a full panel sprayed the compressor will have to refill. When it goes into a fill cycle and even if you stopped to stick by the wait for the duty cycle rule you still ran the compressor for for many times longer than it should have been run. The compressor is going to be short lived.

 

When you properly spray with compressed air your low pressure switch should be set at a 2 psi pressure drop. This means the compressor turns on at 2 psi lower than its max set point. This keeps the spray gun working properly. If your compressor can actually take on the job it will cycle even while spraying. If it can't it will go in the red. Most folks want to believe they can spray with little compressors. There is a big difference between getting fluid out of the gun vs getting it out properly. With little compressors you get a very short proper spray time, seconds and it declines very fast. You will see the spray go from great to crap but you won't see it go from great to good to ok to bad. Its just one extreme to the other and everything in between ruins your finish. So even if you manage a good solid 10 seconds everything in the middle down to the last second is affecting your finish.

 

Most folks wonder why they can't get a factory looking finish at home. They end up sanding between coats or sanding and buffing to get a great finish. Some want to blame the guns and spend loads of money on guns when all they need is a good air source. Granted you do have to pay attention to viscosity and things like that but none of it matters with a crappy air source.

 

Will adding a tank help? Sure in some cases but not with these micro compressors. We run a 7.5hp 3phase rotary screw that puts out 29 cfm with Binks Trophy conventional using 24.4cfm we had to add a 250 gallon tank to it so it wouldn't trigger the low pressure warning in the booth. There is a big difference between running 100% duty cycle compressors and these little units. We run a 20HP Polar Air for the rest of the shop 4 sanders will work it hard and eventually we will add another tank. No way I would put a tank on my little 4cfm emglo at home in the garage and its twice the compressor mentioned above. Hell I doubt I would even think about adding a tank to my 80 gallon two stage Century Industrial. 

[Dan S]

for those that are interested this page provides a decent understanding of the ideal gas law and how it pertains to air compressors.

http://www.alspecialtygases.com/volume_of_gas_in_a_cylinder.aspx

[ponderingturtle]

But a larger tank will help with things like running an impact wrench that wants 10 CFM on a system that provides 4 CFM.  Because you don't run the tool constantly like you do with a sprayer.