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tmeehan 10-12-2007 12:11 PM

Compressor cfm rating required for framing nailer
 
I need to buy a compressor and finish nailer for a project I will be doing. But I want to make sure that the compressor will work for a framing nailer if I ever need to use one in the future. I understand the whole concept of cfm and psi, etc, but as I do my research I find discrepencies in the explanations about how many cfm's are required for a tool with a given rating. Some are saying that if for example the nailer claims to use 4.0 cfm @ 90 psi, then the compressor needs to be a 4.0 (or greater) cfm at 90 psi. That seems easy enough. But others say you should add 50% to the tools rating to determine the compressor rating. One reseller went as far as saying you should double the tools rating. All I know is that I will only be running one nailer at a time. What do you guys (or gals) think about this. I read one post where a person is running two framing nailers with a 4.5 cfi compressor. That's encouraging but I would like to hear what others have experienced. Thanks.

NateHanson 10-12-2007 01:44 PM

I have a PC pancake compressor that I got with a brad nailer/finish nailer combo. Like this one - http://www.toolbarn.com/product/port...2002/?ref=base
This site lists it at 2.6 cfm at 90 psi.

I have no idea how to calculate theoretically what that's good for, but I've used it for everything from brad nailers to a roofing nailer, and a big Bostich framer. With the framer I probably get a dozen shots before the compressor cycles on, and then it's usually done before I've shot a couple more. With the roofer it's even better. I'm usually working alone though, and that slows you down, since you're cutting, fetching, aligning, etc between shots. If I were on a roof whacking at shingles as fast as I could, and someone else was feeding them to me, yeah, I could probably make the compressor run most of the time, and that wouldn't be so good for it (I think duty cycles should be under 50% or so). But as a solo DIYer, I'll never have to worry about that. And I'm really glad I have a small compressor so I can carry it around without any trouble from one job to the next. It means I use it a lot more for smaller jobs.

Clutchcargo 10-12-2007 02:17 PM

I've got the same compressor that Nate has. I only use it with one nailer at a time and I'm not nearly a fast enough worker to make it run low on pressure on a regular basis. The only time that I can beat the compressor is when I'm building headers where there are a lot of nails close to each other. I use it with the Makita AN922.
I had a larger compressor a few years ago (wheels and handle type) that I used for sandblasting and painting. It was big enough to support two nailers. I finished those projects and sold the compressor to a friend where he renovated his house using it.
Although, he has since started a "handyman" business, he never brings it to the job site because he doesn't want to lug it around. The moral of the story is there's a strong correlation between portability and likelyhood to use it.

mdlbldrmatt135 10-12-2007 03:03 PM

Unless it's a Cast iron cylinder I'd say 50% Duty cycle is normal. cast iron are 75-100% Duty Cycles.

Autobody tools (Sanders) are a Huge CFM "sucker" and usualy require a good Cast iton Cylinder (2 stage).

JFXG 04-19-2009 09:53 PM

capacity for sandblasting
 
Quote:

Originally Posted by Clutchcargo (Post 67784)
.....
I had a larger compressor a few years ago (wheels and handle type) that I used for sandblasting and painting....

Is sandblasting pretty much a high demand use? I'm totally new to sandblasting, and have never had to spec my own compressor, either. I need to get an abrasive blaster to clean and derust small parts. A small benchtop cabinet will do, such as http://www.harborfreight.com/cpi/cta...emnumber=42202
This cabinet says it needs 10CFM at 100psi. Based on what I've seen, that seems to mean a fairly large compressor. Am I misinterpreting something? Thanks

micromind 04-21-2009 12:28 AM

Choosing an air compressor involves several factors, mainly CFM and tank size.

If you had a 1 CFM compressor and a 100 gallon tank, you could run just about any tool for a long time. The compressor would run all the time, and store air in the tank when you're not using the tool. If you had a 20 CFM compressor and a 1 gallon tank, again it would run just about any tool continuously. But it would cycle on and off a lot, and wouldn't last very long. Somewhere in the middle is the best way to go.

A framing nailer will use about 2 CFM or less while framing walls. While shooting decking, subfloor, or sheeting, it'll use more like 10 CFM. A small hand-held sandblaster will need about 10-15 CFM. A car body sander uses about 15-20.

Most air tools are rated for a 15 second run time. This means if the usage is listed at 4 CFM, that's what it'll use if operated for 15 seconds each minute. An impact wrench is a good example of this. If you run the tool continuously (like the car body sander), the 4 CFM tool becomes a 16 CFM tool.

Be careful when choosing an air compressor. There's a huge amount of mis-leading advertising. Just because it says 6 HP doesn't mean it'll produce 20 CFMs. The 6 HP rating is the maximum the motor can produce, not what it actually runs at. As a basic rule-of-thumb, at 120 PSI a single-stage compressor will produce about 3-1/2 CFM per HP. A two stage unit will produce about 4 CFM per HP. To determine HP, don't go by what's advertised. Use motor current instead. Basically, a 2 HP motor will use about 10-12 amps at 230 volts. A 3 HP is about 13-16. 5 HP is about 20-24.

Generally speaking, you'll want the largest tank you can put up with. For a stationary unit, 30 gallon would be about the minimum. More is better. A portable unit will be smaller. The larger the tank, the more reserve you have, and the less CFM you'll need. The smaller the tank, the quicker you'll run out of air during heavy usage.

Like just about everything else, there is no perfect solution, what you should get depends on how you plan to use it.

Rob

PaliBob 04-21-2009 12:45 AM

Rob.Good Thinking

JFXG 04-21-2009 04:17 PM

Rob, thanks for that explanation. It has clarified a lot for me.

joel v. 05-01-2009 11:17 AM

You seem to have your question answered but I'll put in my 2 cents. #1- a 15 amp 120 volt motor will never produce more than 2.5 HP. A 20 amp 120v will produce a max of about 3.2 HP. Anything more than that is impossible. #2 If it says 6 hp it's talking about the start up HP. It MAY produce 6 hp for second when starting up. #3 Never ever let a sales person tell you that an oilless pump is better than an oil lubricated pump. They are extremely noisy and don't last anywhere as long as an oiled pump. #4 duty cycle does matter . Pay attenton to it when you buy a compressor. If you find a compressor with a Lesson or Marathon motor on it marked farm use or light industrial with a cast iron pump on it and is belt driven it will be 100% duty cycle. It's when you get in to the direct drive with the little 3450 rpm motors with an oilless pump that duty cycles and durability go down like crazy.


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