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Thread: Are DA sanders too much for 3hp compressor?

  1. #1

    Are DA sanders too much for 3hp compressor?

    I'm getting a new compressor primarily to try my hand at spray finishing. I'm considering the 60 gallon 3HP Ingersoll Rand unit. However, in doing some research around all the things I "may" someday do with this compressor it seems that even one this big may fall short. It's rated at about 11cfm at 90psi... which is about 4cfm short of what is recommended for most DA sanders.

    Question is... Can you run a sander on a 3HP unit with some success, or would it be a complete waste of time?

    In addition to not wanting to spend the extra $ (there is wife acceptance factor involved) to step up to the 5HP unit, I may not have enough power to run it. The only 240V outlet in my garage would be timeshared with a 3HP table saw. I think it may be 30amps. It's really the dryer outlet.

    Thanks!

  2. #2
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    You already know the answer. You will have to stop and wait for the compressor to catch up. If you compare the electricity needed to run an air sander it makes more sense to get an electric ROS than to fire up a 5 hp motor to do sanding. A turbine HVLP would be a better approach for finishing as well. For nail guns and staplers you can use a small portable compressor. With this combination you can work anyhere and not break the bank.

  3. #3
    First a real 3 hp comp. (not one of those 3 hp peak deals) would push a DA sander but probably not at full speed or the compressor would run all most 100% of the time. I went threw this several months ago but for a different reason (sand blasting). I finally made a decision and went bigger than what I needed knowing that I had other plans for it in the future. I purchased an Eaton 7.5 hp. compressor. Been happy as a clam with it and I am glad I went bigger than what would have gotten me by. It stung a little as it was a bit spendy (but no more so than other compressors in that power range), but worth it in the long run, which seems to be the case with WW tools. You mention that you have other things in mind, so I would say try to get what will take you into the future instead of a year from now having to do it all over again. Just my take on it, good luck.
    I know it was here a minute ago ???

  4. #4
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    3HP compressor wont do it, 5hp compressor wont really do it either. Air sander needs 7.5HP TWO STAGE to give you what you want. My 5HP 13.5CFM runs too much and drags a bit under constant duty cycle. Better off with a good electric.

  5. #5
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    Ingersol rand DA sander...CFM at full load listed as 17 CFM...that will kill your compressor quick. Check Festool Rotex.

  6. #6
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    Forgive my ignorance, but why would one want to make such an inventment to run an air sander versus buying an electric ROS?

  7. #7
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    Larry, good air powered DA and ROS can run straight out for 6-8 hours a day for years with minimal maintainence. They are light weight, some have good dust collection, and with an overhead wand to guide the air hose they are quite light and nimble to use. They are ment for a production environment, will last forever if you can push one in your shop. I worked in a custom door shop where we would sand at the end of a production run for days or weeks straight (not much fun).

    Why would a small pro or diy shop need one? Good question. They do spin a bit faster than electric, but doesn't seem to affect end performance.

  8. #8
    For me the sander wouldn't really be for woodworking. I'm restoring an old truck, which is turning out to be a multi-year project. I have compressor envy. People with big compressors have more options.

    Here's a question on the turbine HVLP. A turbine system seems pretty costly too, and other than the portability advantage why would someone choose to go that route over a compressor powered solution?

  9. #9
    Rob Will Guest
    A real industrial grade 3 hp compressor will do a decent job with one DA (I do this all the time). No it will not ever "catch up" but it will run it ok. (I don't think we are talking about all-day non-stop production here).

    Having said that, I use my DA's for metal work only. IMHO, they are too agressive for wood.

    I agree with Rick, an electric palm sander is my choice for wood.

    Rob
    Last edited by Rob Will; 02-08-2008 at 1:19 AM.

  10. There is a HUGE difference between good DA sanders and poor DA sanders. Most of the information you hear regarding air consumption pertains to the poor DA sanders. A good DA sander, like a Dynabrade or MasterPower, will run from a 3 hp (real) compressor, and the compressor will cycle. A $29 DA sander is going to take a lot of air and won't work, but a good sander does not consume that much air any more.

    My workshop has a 5 hp Curtis-Toledo compressor, and I have operated two Dynabrade sanders continuously with the compressor at about 90% duty cycle. This is a high duty cycle, but that is for two sanders afterall.

    Out in the garage I have a 1-1/2 hp (6 hp according to false advertising) portable compressor for taking to jobsites. This compressor will still run a single Dynabrade sander at 100% duty cycle with a slight reduction in pressure and some wait-time. Obviously not ideal, but works for on-site work.

    My father's compressor is about 3 hp (real), and it will operate a single sander (actually he bought my less expensive MasterPower sanders) with an 80% duty cycle.
    ========================
    As for the person that asked why, well once you've used a good pneumatic sander, you would never go back to electric. First and foremost, they will provide a better finish than any electric on the market. Aside from that, they are smaller, more powerful, and easier to handle. They will also last longer, and can be fully rebuilt.

  11. #11
    I just added a Shulz 5 HP two stage unit to my shop. It will run 17.5 CFM and was a great buy when you factor in the quality compared to a Home Depo grade unit. Bought it from the US distributor. You should be OK sharing a circuit with the table saw if you are the only person in the shop. Just don't start the saw if the compressor is running. I have a 110V fake 5 HP Campbell HAusfeld as well, and it is under powered for anything that you want a lot of air for.

  12. #12
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    Quote Originally Posted by George Carion View Post
    ...It's rated at about 11cfm at 90psi... which is about 4cfm short of what is recommended for most DA sanders.

    Question is... Can you run a sander on a 3HP unit with some success, or would it be a complete waste of time?
    You were closer to the truth with the cfm and duty rating. The HP of the motor spinning the compressor makes little difference. For a reference my little 20 gallon tank is nothing to look at. But the cast iron pump can run all day. It was made for spraying (8cfm@40psi) but will push a sander for a few minutes at a time.

    Buy the best air flow you can afford. Sanding on car bodies (just my experience here) is a tedious tiring affair. I can only keep the straight line going a few minutes anyway before needing to move or rest the old arms.

    Jim

  13. #13
    Rob Will Guest
    Quote Originally Posted by Rick Christopherson View Post
    Most of the information you hear regarding air consumption pertains to the poor DA sanders. A good DA sander, like a Dynabrade or MasterPower, will run from a 3 hp (real) compressor, and the compressor will cycle. A $29 DA sander is going to take a lot of air and won't work, but a good sander does not consume that much air any more.
    Rick C. is absolutely right. Some of the el-cheapo DA's use air like an open blow gun.

    Most of my DA's are of the cheap variety.
    I priced a Dynabrade not long ago - nice stuff.

    Rob

  14. #14
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    The pneumatic ROS I used were all top end Dynabrades being pushed by a 15HP screw compressor...no air problem there. They will swirl and ruin your work as quick or quicker than anything. The quality of the job imho is more related to the craftsman than the tool. In my home shop I get great results with my festool 5" and 6", and no dust. I would never put a DA to wood either. The dynabrade will cut a little faster..but swirling less?

    I can sure see the absolute advantage to air when doing autobody, that looks like a lot of work. I might be willing to push my compressor to 90% duty for that. But for wood working I'll skip the carpal tunnel and use my electric. The festool Rotex is marketed as being good for autobody with pads and paper appropriate for that work, of course it is a pretty expensive hand tool and I have no personal experience with it. Cheap pnuematic tools sure do suck (air), I have a few that just won't do.

  15. Had a shop with two 80 gallon compressors. One was a 3 hp, and the other was a 5hp. Both were 3 phase. They drove the old Quincy 2 stage heads. (I still have one of the Quincy 2 Stage heads, they easily weigh over 200 pounds, just for the head) They put out 17.5 SCFM at 175 pounds of resistance. I had them joined at the outfeed tube from the tanks. Never ran out of air, even with 11 people. Some spraying, some running DA's, and others talking.
    The point I really wanted to make, was that these motors also weighed a ton. I took one home, and wanted to remove it from the trunk of the car and was unable. I finally used a chain hoist attached to a beam from the ceiling. I have that sitting waiting to be hooked up to the Quincy head again. Meanwhile I bought a 6hp Campbell Hausfiled, and there is no comparison. The 6hp in the CH is equal to half of the production of the 3hp monster. It has nothing to do with 3 phase, or not, it is just an industrial grade motor. Think of it this way, the motor on my Bosch router is 3 1/2hp, and it weighs 13 pounds or so. I know that is a different motor altogether.

    The bottom line is this. What is the compressor rated at, at how many pounds of pressure. So if the tank is at 100 pounds, what is the motor and pump putting out at that much resistance. (As long as the manufacturers numbers are real) Then see what the tool calls for. If you have a 15scfm sander, and you are only putting out 9, you will sand, and wait, sand and wait.

    You can daisy chain compressors to share the same outgoing line as long as they are rated at the same pressures. The safety pressure release valve needs to be the same, otherwise the lesser unit will keep blowing out the valve. So if you have a compressor in the garage, and one in the shop, by combining them, you will get twice as much air. I have the one, and run a line down into the wwshop from the garage.

    I am a little concerned about running your table saw, and compressor off of the same line, although if it is rated for sufficient amperage to handle both, I guess it would do. The problem I have found is that compressors require a bigger bite at startup, then do most tools. Even with the air release when it stops, in order to take the pressure off of the heads, the initial startup is still a compression stroke, and a long one at that. In comparison a table saw, will spin to full speed in a millisecond. No resistance there. So maybe you should do some more looking into what loads there are on each, and see if the circuit will handle it. The other consideration is that compressors have a way of kicking on whenever they want. A leaky air tool line, with a tool left plugged in, or any slow hiss sound is a slow leak, and that will cause the compressor to recycle. If by chance you are starting the table saw at the exact moment the compressor decides to kick on, that could bind the air compressor. Gnawwwww click. There goes the breaker. Maybe not, I used to have an old 2 hp Sears air compressor, 240 volt, and the pressure release valve stuck occassionally, and the gnawwwwing sound and click, became familiar.

    I remember when I closed my shop, I sold one of the compressors, with the 5 hp, and the 80 gallon, and Quincy head for $200. It was a circa 1966 and still ran like a tank. (No pun intended)
    Last edited by Bob Feeser; 02-08-2008 at 4:43 PM.
    "Fine is the artist who loves his tools as well as his work."

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