# good air compressor...?



## EmilioG (Nov 23, 2014)

I'm shopping for a good small. portable, electric air compressor for my air powered
tools, i.e. 25K RPM die grinders, etc..
What would you recommend? I'd like it to be somewhat quiet and durable.
What do I look out for?
I will look at used as well.
Thanks


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## xalky (Nov 23, 2014)

Cfm capacity is your benchmark. Look at the tools you'll be using and Thier corresponding cfm requirements. Add 30-50 percent extra and that's the size compressor you need. When in doubt, go bigger. You'll find that die grinders are very heavy on air requirements. You won't find a "small" air compressor that'll run a die grinder for very long.


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## Dave Smith (Nov 23, 2014)

if you will be using die grinders and high cfm tools then a large(60-80) air tank is more important than the compressor, which should be at least 11cfm or higher.----Dave


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## JimDawson (Nov 23, 2014)

To run a standard die grinder requires about 4.5 CFM @ 90PSI.  So you are looking for a minimum of a 3HP compressor and it will run pretty continuously when running a die grinder.  For commercial wood working use, I normally figure 5 HP for each air sander.  If you want quiet, be prepared to spend a lot of money.  They exist, but they are not cheap.

My 5HP (a true 5HP, not the ones that are said to be 5HP) runs about 50 % of the time when I'm using my die grinder.

A true 5HP compressor motor draws about 25 amps at 240V.  Always look at the amp draw on the motor.  Roughly 5 amps / HP @240V and 10 amps / HP @ 120V

Many of the so called ''5HP'' compressors have ''Special'' stamped on the motor data tag in place of an actual HP number.  These are not 5HP compressors and I have see some that were actually closer to 1HP.

So having said all the above, HF is not a terrible place to buy a compressor, there are also the big box stores and farm supplies.  If you are looking for used, Craigslist is a good resource.  Just watch the HP rating.


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## Mark in Indiana (Nov 23, 2014)

Look for an "industrial" compressor. Brands like Ingersoll Rand, Quincy, Gardener-Denver, etc. You will pay more, but you will only have to buy it once. I had a 2/hp. Ingersoll Rand for over 30 years. It ran everything from paint guns to sanders. Sanders were a little slow, but not unacceptable for my needs. The only reason that I no longer have it is because I traded up.


Happy Trails


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## JeepsAndGuns (Nov 23, 2014)

Stay away from "oil less" compressors of any type. Running something that has a high demand of air like a die grinder is goona over heat and kill a oil less compressor in short order. 
What you want is a belt driven cast iron oil type compressor. I really love my ingersoll rand model 242 compressor. Its on a 80 gallon tank and has a 5HP 230v motor running it. It holds up really nicely but even it cycles a good bit when I am doing some heavy die grinding. 

Small and portable are not words for a compressor that can handle die grinders. If its small enough to transport easy, its going to be working hard to keep up with them, if it even can. If its big enough to handle them, its not gonna transport easy.


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## Andre (Nov 23, 2014)

In the barn there is a 60 gallon CH compressor, the pause between pumping up's is around a minute with a HF pencil grinder. Die grinders use a ridiculous ammount of air. A pancake or hotdog compressor? Forget about it.....


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## f350ca (Nov 23, 2014)

I have a Makita electric die grinder thats gone through two sets of bearings over the years. Had to buy an air operated one when one of the sets of bearings went and I had to wait for replacements but had to finish a job. The sound of a 5hp compressor running most of the time to feed it drove me nuts while thinking the electric one would be drawing 5 or 6 amps on 110 instead. Could never see the point of most air operated tools.

Greg


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## fixit (Nov 23, 2014)

EmilioG said:


> I'm shopping for a good small. portable, electric air compressor for my air powered
> tools, i.e. 25K RPM die grinders, etc..
> What would you recommend? I'd like it to be somewhat quiet and durable.
> What do I look out for?
> ...



Do not buy a high speed (3450 PPM) compressor, they run hot & you end up with lots of water. They also have shorter life. I find for shop use a 5 hp 240 Volt 1740 (1800) RPM Motor, 3 or 4 cylinder pump turning about 750 RPM feeding a 60 to 80 gallon tank is about as good as you need. True bigger is better but 7,5 Hp & up really get expensive.


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## GarageGuy (Nov 24, 2014)

As mentioned above, avoid oil-less compressors like the Plague.  They are loud, and they die young.  A belt driven cast iron compressor with an oil sump is quieter, pumps more air, and should last for decades.  

Rather than trying to match a compressor to your initial air tool purchase, I recommend getting the largest compressor you can find in your price range.  My reasoning is:  you will always be getting more air tools.  First are die grinders because they are cheap and handy, but soon you'll want sanders, grinders, impact wrenches, and even sand blasters.  They are great tools, and you'll use the heck out of them.  If you get a big compressor to start with, you won't be trying to upgrade in a year.

I bought what I *thought* was a big enough compressor.  It was a 3HP twin cylinder with a 30 gal tank from the DIY store.  It ran in the 90-120 lb air pressure range.  It seemed like a big compressor until I really started to use it.  Long story short, I was looking again within a year.  I found a big used 220v 5HP stationary compressor with a 80 gallon tank for cheap that just whups up on any of the portable ones.  I run 175 lbs of air pressure, and can sand blast continuously while the compressor cycles off to rest.  Now I can get real work done.

Just my $.02

GG


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## Dave Smith (Nov 24, 2014)

right on GG---my compressor is a 60 gallon tank 5 or 6hp and I add on extra storage tanks using quick connects when I need a lot of quiet air--the storage tanks can be outside under a cover so they don't take up shop space---the large propane tanks work good for extra storage---just put good ball valves on tanks to seal them off when not using and check your system for any leaks--they will waste a lot of air---I have about ten compressors in different sizes--and my quietest one is a 4 cyl compressor off an refrigeration unit---it doesn't pump up as fast to 120psi but it runs so quiet you can hardly hear it----I haven't got 220 wiring to my new shop yet, and when I do then I will start selling or trading my smaller compressors.----three compressors should be enough,----just remember you can get by now with a smaller compressor as long as you have an 80 or bigger storage tank and others to connect on.--I would look for an older large air compressor for sale---lots of people think the smaller newer compressors are better--so you may pick up a large one cheap----Dave


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## GK1918 (Nov 24, 2014)

Mark in Indiana said:


> Look for an "industrial" compressor. Brands like Ingersoll Rand, Quincy, Gardener-Denver, etc. You will pay more, but you will only have to buy it once. I had a 2/hp. Ingersoll Rand for over 30 years. It ran everything from paint guns to sanders. Sanders were a little slow, but not unacceptable for my needs. The only reason that I no longer have it is because I traded up.
> 
> 
> Happy Trails



The proof;    in our shop bought new by my father in 1939 dual stage Ingersoll Rand 2 stage 5hp 220 1 phase vertical 80 or +gal . anways its never been touched workes
just about 7 days aweek and parts are still available...
sam


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## mzayd3 (Nov 24, 2014)

Scfm of the pump dictates the size of the tool you can continuously drive.  The volume of the tank dictates how often the pump kicks on.  That said, go huge, as big as you can.  If I had to skimp on something, I would make it the tank size.  Get as many scfm that you can afford.


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## nickmckinney (Nov 24, 2014)

f350ca said:


> ....Could never see the point of most air operated tools....



Our compressor runs the blast cabinet, paint booth, blow guns, and once in a blue moon an air tool. I too prefer electric wherever possible.

I rebuild/sell new compressors in the dental world where they are near silent and 100% duty cycle even when oil free but man you pay a price for that (one I just sold was over $7K, 2HP, and installation was NOT included at that price)


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## chips&more (Nov 24, 2014)

Well, you are all right, but sorry, I like my set-up better. I have 5 portable compressors that feed a common manifold that supplies the shop air. Each compressors pressure switch is adjusted for a 8psi difference from the others. The highest setting is 130psi. That compressor which is set at 130psi is the only one that turns on for the majority of the air demand in the shop. If I do any high demand CFM like sand blasting then eventually all five compressors might turn on. The one main/first compressor is the only one that runs for about 95% of the air in the shop. This way I don’t have a big bertha compressor always turning on.  It’s only a $50 flea market find (and it’s been about 10 years and the darn thing has not died yet). And if I need more air/CFM, more compressors automatically turn on…Good Luck, Dave.


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## Downwindtracker2 (Dec 2, 2014)

There are some good points:
Go by amps draw, not advertised  H.P., my "5hp" draws 15 amps ,so does my 3hp table saw, both at 220volt .
10 SCFM is a minimum for a home shop, 3hp, that's the cut off for most spray painting.
Better quality air tools use less, some times much less air.
The pressure drop over line length is very noticeable, don't use 1/4" hose
Air tools are nice, you are not packing a heavy motor.


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## coolidge (Dec 2, 2014)

JimDawson said:


> To run a standard die grinder requires about 4.5 CFM @ 90PSI.  So you are looking for a minimum of a 3HP compressor and it will run pretty continuously when running a die grinder.  For commercial wood working use, I normally figure 5 HP for each air sander.  If you want quiet, be prepared to spend a lot of money.  They exist, but they are not cheap.
> 
> My 5HP (a true 5HP, not the ones that are said to be 5HP) runs about 50 % of the time when I'm using my die grinder.
> 
> ...



I was comparing 3hp to 5hp motors offered by a machine vendor...they were spec'd as drawing the exact same amps at 240V...yeah I wasn't born yesterday.

PS: I admit to lusting for a rotary compressor.


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## John Hasler (Dec 2, 2014)

coolidge said:


> I was comparing 3hp to 5hp motors offered by a machine vendor...they were spec'd as drawing the exact same amps at 240V...



That number is the rating of the circuit that they can be connected to.

Manufacturers do often lie about motor ratings, though.  They state the peak short-term output rather than the continuous rating.


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## COMachinist (Dec 2, 2014)

Hi All
I picked up one of these to use in the shop for little things that don't need my 80 gal, 10hp 2 stage. that thing will drive you nuts when it runs. http://www.ebay.com/itm/SALE-Califo...-Lab-Ultra-Quiet-Air-Compressor-/351242896390
I don't have any connection with these people but I like their service and they shipped fast. I use it to run my cut-off tool and die grinders as well as my Fog buster, and the air power drawbar on my CNC. you will be amazed at how quiet it is.
Here you here it run.
https://www.youtube.com/watch?v=otME04bL2PA
Happy Machining
CH


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## sgisler (Dec 2, 2014)

Wow! That's crazy quiet. Price seems really good too!


Sent from my iPhone using Tapatalk


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## cvairwerks (Dec 3, 2014)

A larger compressor coupled with additional tankage is your friend. I'm about to install an Ingersol Rand T-30/243 here at the house, as soon as the single phase motor gets here. It has a 120 gallon tank and will be coupled to a 650 gallon ex-propane tank. If I hadn't been able to buy it all so cheap, I would have sprung for a Kaiser screw compressor package instead.

A cheap way to add tankage is garage sale compressors that have burned up pumps or motors. Strip the stuff off the tank and plumb together. It's easy to hide the tank in the rafters or the attic.


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## coolidge (Dec 3, 2014)

John Hasler said:


> That number is the rating of the circuit that they can be connected to.
> 
> Manufacturers do often lie about motor ratings, though.  They state the peak short-term output rather than the continuous rating.



No this was the actual draw in amps peak.


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## coolidge (Dec 3, 2014)

COMachinist said:


> Hi All
> I picked up one of these to use in the shop for little things that don't need my 80 gal, 10hp 2 stage. that thing will drive you nuts when it runs. http://www.ebay.com/itm/SALE-Califo...-Lab-Ultra-Quiet-Air-Compressor-/351242896390
> I don't have any connection with these people but I like their service and they shipped fast. I use it to run my cut-off tool and die grinders as well as my Fog buster, and the air power drawbar on my CNC. you will be amazed at how quiet it is.
> Here you here it run.
> ...



I am so buying their 10 gallon, love how quiet it is.


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## cvairwerks (Dec 3, 2014)

The CAT compressor is interesting, but when you read the manual for the 2 hp unit, max working pressure is 75 psi and it says it will overheat if used for more than 1 hour continuous. I think you will find that it's more suited to running a very low flow tool on an intermittent basis rather than with higher flow tools for longer periods.


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