Official Luthiers Forum!

I am not very familiar with air compressors - okay, I know absolutely
nothing about air compressors

I am purchasing an 18" Grizzly Wide-Belt in the next couple weeks and it
requires 57 psi for the pneumatic control. I really don't have room for
one of the really big tank compressors and I don't want to spend much
more than $300. I also would like to run the motor thru 115 volt to avoid
having to run another line.

I have heard that the oil compressors are much quieter than the oil-less -
that seems like a big benefit to me that far outweights any mainetance.


So can anyone recommend a good air compressor that will meet the 57
psi requirement for the sander without having to run constantly. It also
might be nice to have a compressor that has enough power to run one of
the air-powered finish sanders.

Appreciate any help you can give.

Thanks,
Simon

Trust me on this one. You can get one for $300 that will get the job done for you now,BUT you will be buying a larger capacity later down the road and these thing don't have much of a trade-in value

Don't ask me how many time I have upgraded to just enough to get the job done. only to need more capacity later

Micheal,
Could you recommend what you think would be a good minimum then? I
don't want to spend money on something and then wish I had spent a
couple hundred more. But as I said, I don't have a lot of room - so one of
the 60 Gallon compressors is not practical for me right now.

And the only thing I see myself using this for is the Grizzly which requires
57 psi and maybe a nice Dynabrade finish sander.

Cheers,
Simon

Practically any compressor will provide 60psi, and the thickness sander probably won't need a lot of volume (cu ft per min, cfm) of air. On the other hand, running a air sander (disc or ROS) can require quite a bit of volume- you should check the specs on the type of sander you're considering.

It's usually the cfm rating that's the problem, and getting lotsa cfm is what costs money.

Small compressors are so cheap that it might be worthwhile getting one while you are working up to the 'big mutha'. I recently bought a $120 Chinese-made compressor that delivers 4 cfm @ 90psi- it's reasonably quiet, and provides enough air for a small HVLP gun (Walcom) and for blowing dust around and pumping up tires. My neighbour borrows it (or the smaller $40 one) to carry around and run his nail gun for his basement reno project. I had enough money left in the budget to get some decent filters and air lines- when I get a bigger compressor, I can just plug it in to the air lines and filter bank.
BTW, don't buy a compressor without hearing it run- some of them (mostly the cheaper and smaller ones, but not only those) are extremely noisy.

Cheers

John

I agree 100% with Michael. "Sneaking up" on what you really need when buying tools usually ends up costing lots more in the long run. I thought I learned this years ago when buying photo and darkroom equipment. I was wrong.

_________________
now known around here as Pat Foster
_________________
http://www.patfosterguitars.com

This a good pretty good spec

7 hp
60-gallon tank
15 amps @ 240 volts
135 PSI
SCFM Air Delivery 14.2 @ 40 PSI / 9.7 @ 90 PSI
$525 delivered from Grizzly. It should cover most anything you want to do. It is what I am using now.

I don't get why those PC compressors put out so little air with so much horsepower, although that is a great price. My 5HP DevAir pumps out something like 14 or 18CFM @ 120PSI (tank compresses to 150PSI). It just seems like there must be some inefficiency there for all that power to produce so many fewer CFM.

Air sanders suck up CFM like nobody's business. I think that, run simultaneously, the coolant pump and venturi vacuum on the Fadal take up as much air as the sander does by itself. And it's just a 3.5" Mirka.

For something using just a little air intermittently, you're much better off with a small pump and big tank. It'll take forever to fill up the tank, but once it's full you probably won't cycle very often. With something like a sander, you need all the pump you can get and it'll be cycling all the time even with a big tank.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

[QUOTE=Bob Garrish]I don't get why those PC compressors put out so little air with so much horsepower[/QUOTE]

The reason is because they lie.  The average consumer that walks into Home Depot sees the HP rating on a tool or piece of equipment and their wallet starts jumping around in their pants.  It doesn't mean it's a bad compressor or a bad bargain, it just doesn't have the claimed HP.  As previous posts have said, what matters is CFM, which is usually measured somewhere between 60 & 120 psi.

HP rating is a very unreliable gauge of actual motor size - for most consumer grade products the manufacturers generally label the HP at whatever they think will make the unit sell the best.  Compare amperage ratings and remember that when running on 110V the amperage rating on the motor plate will be double what it otherwise would be if the motor was running on 220V.  Imported Asian motors are generally less efficient that USA made motors like Baldor and therefore require more amps to produce the same HP.

Back to the original question, you should be able to get a servicable compressor for $300, but don't expect a lot and it will likely cycle on and off a bit because of the smallish air tank - the larger the tank the fewer on/off cycles at any given use rate - generally speaking. Oh - avoid universal motors for shop applications - stick with an induction motor. 

 

Since the early 80's tool companies have been allow to rate HP on power tool by the peak HP. In other words the max available HP at optimum conditions under no load, not the mean average or constant duty HP. A typical 5 hp electric power tool actually produces only about 3.8-4.5 HP in mean average continuous servers. However in the industrial electric motor industry things are much different. So basically the company that builds the motor is truthful to the tool manufacture about the working capabilities of the motor in the tool. But the tool retailer advertises peak efficiency only.

i am unfamiliar with the need for comprssed air in your wide belt sander application. what does it control? does it specify a volume requirement? is the usage constant or intermittent? these questions need to be answered before making your decision on what eill fulful your current needs.

as regards the future, as others have said air tools, and ros in particular, tend to use a high volume of air, at fairly high pressure. i have been considering going to air ros and my current compressor won't handle them. most manufacturers seem to recommend on the order of 16cfpm @ 90psi as the air production required. this means a sizable compressor. i have read anecdotal reports of running one on a 5hp compressor but it required the compressor to run constantly, that is a 100% duty cycle. to avoid this you would probably have to go to a 7.5hp unit. i would like to hear the experiences of those actually using dynabrade or other ros units.

I just check the Grizzly site for your sander, but it doesn't say what the CFM requirement is for the pneumatic tension/oscillation features.
Give them a call and get the spec.
BUT, as already stated, spend the few extra $$$ (maybe a couple hundred) and get a compressor that will handle all now, with room to grow. The vertical compressor in a previous post will only take up the space of a water heater. Stick it in a corner, strap it down with some water heater earthquake straps, feed it 220V and you will be good for probably the rest of your wood working career. That's what I did and I never regretted it. Maintenance it yearly (change oil and intake filter) and it will probably run forever. Check out a Grainger store (or online) and see what they have. I got mine through them 6 years ago and it has been bullet proof. The compressor is rated for a 6,000+ hour life. IF it ran for 2 hours everyday (unlikely) it still would go almost 10 years!

DO NOT get an oil-less. They will drive you, and your neighbors, deaf!

_________________
Hank Mauel

I just did a quick Google search, and many do not give the specs, but the Eagle and the Porter Cable Pneumatic ROS's both require 15CFM@90 lbs.  That's a lot of air.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Humm sounds like it is using pneumatic cylinders for the osculation???? seems a wasteful energy consumption.

The air volume specified for ROS and other tools is a maximum (if not more). In my experience, they can get by with considerably less. I have easily run smaller pneumatic tools on my old 2 hp compressor at nowhere near 100% duty cycle.

You are probably right.  I did see a Pn finish sander yesterday that said it took an average of 6 CFM.  That seems more reasonable.  But that was a little square finish sander,  I couldn't find it again, and I don't remember what the brand was.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

[QUOTE=MichaelP] This a good pretty good spec

7 hp
60-gallon tank
15 amps @ 240 volts
135 PSI
SCFM Air Delivery 14.2 @ 40 PSI / 9.7 @ 90 PSI
$525 delivered from Grizzly. It should cover most anything you want to do. It is what I am using now.
[/QUOTE]
I have this air compressor and it is more then adequate for most projects, not quite up to an air sander. What disappointed me is the duty rating, only 50%, so on heavy applications you can only in reality get half the rated performance. Lowe's has similar sized compressors under 500 that are 100% duty rated. also the 7hp thing is a fairy tale.

Yeah, it's like that 6.3 HP vacuum I have.

_________________
Waddy

Photobucket Build Album Library

Sound Clips of most of my guitars

Thanks for the information. You all have been very helpful.

Peace Out,
Simon

My 5HP, which has a Baldor motor, can run my air sander as much as I can use it without running constantly. It gets close, though.

The CFM ratings for tools, normally, are for a 25% duty cycle. It certainly makes a difference, because I made the mistake of thinking my old compressor could run a sander...it could, but only for 15 seconds at a time followed by a minute of waiting.

_________________
Bob Garrish
Former Canonized Purveyor of Fine CNC Luthier Services

Simon,
Before you settle on an air compressor, be sure to take in consideration the amperage it will take to start up and run. You mentioned that you do not wish to run a separate electrical line. This means that whatever you have using power on the same circuit will be competing for amperage with the compressor when it is operating. It is really not feasible to have a large compressor(high amperage) running simultaneously with other machines. It may be a pain in the @ss, but run a new 240 volt line with 10 gauge wire and you will never be sorry you did. If you cannot do it yourself, find an electrician friend or even bite the bullet and pay for it. It is the second step in installing the compressor. Of course, as mentioned by other members, the first step is finding the correct size compressor based upon the cfm you need to run the tools you have or plan to have.
good luck,
chris

_________________
Chris Oliver
Infinity Luthiers
...in the shop.

live every minute...

i would rate getting the power on to be step three; i) find the right machine, ii) decide where to put it taking into account what shop air lines you want to plumb, noise and possible enclosure with your dust collector, etc., and iii) get the power to the machine.

depending on the size of dust collector you are going to be using, and with a wide belt sander it will need to be a significant machine, you just may want to run THREE new 240v circuits. oh, yeah, i didn't mention that the sander will require a 240v ciruit also.