air compressor question

[Sawatzky]

My brother-in-law wants an air compressor for his B-day. He wants to use it for airing up tires and an air rachet and impact wrench. How much CFM and PSI and how large of a tank will he need to run these tools? How are the air compressors that HF sells?

[crokett]

A quick check at the HF site on the air tools shows them to be all around 4 CFM at either 90 or 100 PSI. I think air tools put a bigger demand on a compressor than something like a nail gun though. Nailers are bursty. Air guns or sprayers need sustained air.

[Uncle Cracker]

Every tool is different, but a good rule of thumb is that the most greedy (in terms of CFM's) are things like sanders, scalers, cutoff tools, and big (1") impact drivers. Many of these can require 12-CFM or more. Those that require prolonged "on" times, like a sander, rather than short bursts, can really load down a moderate compressor.

[Worley]

I would stay away from HF compressors. I had a smaller compressor from there that seized up after only a few uses. For a little more money you can get something that has a better motor and better customer service should something go wrong.

[Bill in Buena Park]

I now have this one:

http://www.sears.com/shc/s/p_10153_1...ir+Compressors

I had one like this, and it ran my impact drivers and such just fine:

http://www.sears.com/shc/s/p_10153_1...ir+Compressors

Bigger tank = longer run time between recharge, my rule-of-thumb has been to check CFM output at 90psi, where I think a tool like an impact driver, if used alot, wants to be ~4CFM or better, with at least a 20g tank. Otherwise, you may frequent recharging interruptions.

[mpc]

For weekender garage work, a 12 or better yet 20 gallon compressor rated at 6CFM @90psi will do a lot - regular paint guns, air impact guns, nailers, etc. Air powered sanders often require much higher CFMs as do "high volume low pressure" paint guns. The CFM ratings at pressures below 90psi don't mean much except maybe for paint spray guns; no air tools use low pressures.

Many compressors on the market now proudly blab about 150 or even 200psi... but have crummy low CFM ratings. CFM is everything! Few tools need more than 90psi; most actually max out at 90 to 100 psi so a 150 psi compressor just works itself hard for nothing - you have to regulate that high pressure down to what the tool requires. Air tools work on air FLOW more than air Pressure ==> that's CFMs. High air pressures can be useful if you have truck or RV tires to inflate though.

Like shop vacs, many air compressors have highly inflated horsepower ratings. For a regular 120 volt wall outlet around 2 horsepower is all you can get out of such an outlet without popping breakers/fuses. Look at the label plate on the motor for horsepower or amperage ratings - ignore the big stickers plastered to the plastic covers of the compressor.

The other thing to consider is oiled vs. oil-less compressors. Oil free compressors are everywhere now. They tend not to last as long and are usually wake-the-dead loud. Compressors with oil in the crankcase need a little simple maintenance now and then and perhaps an oil separator/filter in the air hose when you're using it to drive a paint spray gun. Usually a new compressor won't leak "oil mist" into the air but a well-worn one might let some oil into the airflow... that doesn't do paint any favors.

It's a good idea to have two separate air hoses: one for air tools and one for painting. Why? You have to dribble a few drops of oil into air tools prior to use; often some of this oil runs back into the hose. Keep a separate "clean" hose for painting only.

A while back, a BT3 member posted the US General compressors from HF had a low failure return rate while the other brand was far more problematic. If I remember correctly.

mpc

[LCHIEN]

i'm going to go a little contrarian and say that a 4 CFM compressor will handle brad nailers just fine. And will run light duty ratchets and impact wrenches. and air up tires OK.

So I'm going to qualify that and say as a homeowner he's only going to be topping off one or two auto tires, not filling 18 large truck times just mounted.
And that he's going to be alternately aligning and starting nuts then putting them in with the tools.

Because even slow, he'll top off the one or two tires soon enough and will be putting on just a few fasteners in a production environment.

I've used ratches and impact wrenches briefly to do a few nuts and bolts with my 8- gallon pancake compressor. like assembling tool stands and changing tires. The tank will give you some brief extra CFMs for many seconds. And it only takes 3-4 seconds to put a nut on anyway with such a tool. Then you lay down the tool to put the next bolts in while the tank recovers.

Now I don't think I'd do grinding or spray painting with it, those use a lot of air for relatively long stretches of time.

so to the OP, get a compressor which takes 15A at 120V (that'll give you the max airflow rate, ~4 to 4.5 cfm, you can get at 120V mains) and a tank of at least 6 gals. preferably as much as 12 or even 20 gals if you can.

[eccentrictinkerer]

I have a tiny Senco 1 Gallon, 1 HP, 0.6 cfm compressor I take to job sites. It handle my 16, 18 and 23 ga. brad nailers just fine. I've used it for 5 years now without a hitch.

My old 2 HP Ingersoll handle my PC framing nailer just fine. I only use the big dog Craftsman 6 HP for painting and air tools.

Earlier posters alluded to noisy oil-less compressors. I agree.

I bought a 5 HP Craftsman and had in the shop for 1 hour and back it went.

Old iron is still best, IMO!

[LinuxRandal]

For weekender garage work, a 12 or better yet 20 gallon compressor rated at 6CFM @90psi will do a lot - regular paint guns, air impact guns, nailers, etc. Air powered sanders often require much higher CFMs as do "high volume low pressure" paint guns. The CFM ratings at pressures below 90psi don't mean much except maybe for paint spray guns; no air tools use low pressures.

Many compressors on the market now proudly blab about 150 or even 200psi... but have crummy low CFM ratings. CFM is everything! Few tools need more than 90psi; most actually max out at 90 to 100 psi so a 150 psi compressor just works itself hard for nothing - you have to regulate that high pressure down to what the tool requires. Air tools work on air FLOW more than air Pressure ==> that's CFMs. High air pressures can be useful if you have truck or RV tires to inflate though.

Like shop vacs, many air compressors have highly inflated horsepower ratings. For a regular 120 volt wall outlet around 2 horsepower is all you can get out of such an outlet without popping breakers/fuses. Look at the label plate on the motor for horsepower or amperage ratings - ignore the big stickers plastered to the plastic covers of the compressor.

The other thing to consider is oiled vs. oil-less compressors. Oil free compressors are everywhere now. They tend not to last as long and are usually wake-the-dead loud. Compressors with oil in the crankcase need a little simple maintenance now and then and perhaps an oil separator/filter in the air hose when you're using it to drive a paint spray gun. Usually a new compressor won't leak "oil mist" into the air but a well-worn one might let some oil into the airflow... that doesn't do paint any favors.

It's a good idea to have two separate air hoses: one for air tools and one for painting. Why? You have to dribble a few drops of oil into air tools prior to use; often some of this oil runs back into the hose. Keep a separate "clean" hose for painting only.

mpc

What he said. The oil-less ones also tend to use aluminum heads, rather then iron. The iron one lasts longer.
Also, CHEAP, low power air tools, like an HF impact wrench, are going to be rated differently, then say an Ingersol Rand 2135Timax. (what I used wrenching)

JMHO, give him $$$ towards a compressor. Allow him to either add to it (get a larger one then he needs, as you grow into them), or buy one based on his use/wants/needs, and don't be the bad guy who bought him too small of compressor.

[cabinetman]

For weekender garage work, a 12 or better yet 20 gallon compressor rated at 6CFM @90psi will do a lot - regular paint guns, air impact guns, nailers, etc. Air powered sanders often require much higher CFMs as do "high volume low pressure" paint guns. The CFM ratings at pressures below 90psi don't mean much except maybe for paint spray guns; no air tools use low pressures.

Many compressors on the market now proudly blab about 150 or even 200psi... but have crummy low CFM ratings. CFM is everything! Few tools need more than 90psi; most actually max out at 90 to 100 psi so a 150 psi compressor just works itself hard for nothing - you have to regulate that high pressure down to what the tool requires. Air tools work on air FLOW more than air Pressure ==> that's CFMs. High air pressures can be useful if you have truck or RV tires to inflate though.

Like shop vacs, many air compressors have highly inflated horsepower ratings. For a regular 120 volt wall outlet around 2 horsepower is all you can get out of such an outlet without popping breakers/fuses. Look at the label plate on the motor for horsepower or amperage ratings - ignore the big stickers plastered to the plastic covers of the compressor.

The other thing to consider is oiled vs. oil-less compressors. Oil free compressors are everywhere now. They tend not to last as long and are usually wake-the-dead loud. Compressors with oil in the crankcase need a little simple maintenance now and then and perhaps an oil separator/filter in the air hose when you're using it to drive a paint spray gun. Usually a new compressor won't leak "oil mist" into the air but a well-worn one might let some oil into the airflow... that doesn't do paint any favors.

It's a good idea to have two separate air hoses: one for air tools and one for painting. Why? You have to dribble a few drops of oil into air tools prior to use; often some of this oil runs back into the hose. Keep a separate "clean" hose for painting only.

A while back, a BT3 member posted the US General compressors from HF had a low failure return rate while the other brand was far more problematic. If I remember correctly.

mpc

MPC has a good summary. If you figure the most CFM's of the tool you use, remember that the tank size is relatively unimportant as it is the reserve air to the tool when the compressor cycles off. When the tank depletes to the "kick on" setting, it has to fill the tank and support the tool at the same time.

If the CFM's of the compressor are lower than the demand, it will continue to run, and not support the tool, producing hot air. Not good for painting. Short burst usage like nail guns can operate on the smaller compressors.
.

[JimD]

I will second the "smaller is still useful" sentiment. I have a Bostitch compressor I bought in combination with a 16 gauge finish nailer. It is not 15A, it is more like 10A. It is plenty adequate for my nailers and staplers - the 16 gauge is the biggest (I also have a 18 and 23 gauge and a couple staplers). I use it occasionally with an impact wrench to remove the blade of my mower to sharpen it (I need to do it now). Because it has a tank, it will do this fine too but if you were trying to restore a car or something and using air tools a lot, you would want something bigger. I have also painted quite a bit with my little compressor using a Wagner conversion gun. It works, sort of. If all the adjustments are just right it will spray a pretty good if somewhat small pattern (maybe 6-8 inches). It runs constantly and will only give me about 6psi at the gun - which can work but gives no margin. I will probably use some tax return money to buy a Fuji blower/gun setup because I am tired of the "sort of" job my little compressor and conversion gun do. I could get a bigger compressor but I am pretty sure the Wagner is part of my problem (it's adjustments are pretty hard to dial in and it doesn't seem to hold them).

So to me it matters how seriously your brother-in-law wants to do things like air tools or spraying. I have a cutoff tool that just essentially will not work with my compressor. It needs too much air. For an occasional use of an impact wrench, however, it is fine. Nailers can be driven by even smaller compressor. I air up a portable tank when I need to drive a few nails away from a compressor.

Jim

[dbhost]

I currently have a Central Pnuematic 2HP 8 gallon air compressor. And I am certain I overwork it... But it is holding up fine.

I mostly use it for nailers and airing up tires. The tools / tires used are...

HF framing nailer, finish nailer, and pin nailer.
HF spray gun (not in long runs, just short bursts, and I wait for the tank to refill before proceeding.)
Blue Point 3/8" and 1/2" impact wrenches.
Blue Point air ratchet. (This beats up the compressor pretty good).
Blue Point die grinder. Same as the air ratchet.
Ingersoll Rand Air Hammer.
35x12.50/17 LT Mud tires.

The air ratchet and die grinder tend to cycle the compressor a lot. The compressor cycles once per tire. Other than that, it keeps up with what I am doing...

Would I like a big 60 gallon 220V compressor in my shop? Sure. But I don't have the money, and honestly, don't have the space for a big compressor. This little HF compressor does what I need it to.