How much air is enough?

I have various air tools and they seem to be ok, then I bought a 3" circular
metal high speed cutter and my compressor couldn't keep up. Every 10 seconds
I have to stop the saw and wait for the compressor to catch up, PITA.
I have a real 2 hp, 230V, 20 gal compressor rated at 7.7 CFM @ 90 PSI but
the cutter is only rated at 5 CFM @ 90 PSI. That doesn't make any sense.
What gives?
Reply to
Frank
Loading thread data ...
the cutter is only rated at 5 CFM @ 90 PSI. That doesn't make any sense. What gives?< Sounds like someone didn't put down the right specs. In my experience air tools like drills and screwdrivers use from 8 to 10 cfm @90psi.
dennis in nca
Reply to
rigger
It's real simple. The air tool is rated at 1/10 duty cycle. :-)
As for how much air is enough well that depends on what you're doing. There never seems to be enough air till you go really overboard. To see my solution look on my home page below and look under "portable air compressor".
Wayne Cook Shamrock, TX
formatting link
Reply to
Wayne Cook
"Frank" wrote in news:qcGdnXQamMJrX8fenZ2dnUVZ snipped-for-privacy@comcast.com:
Losses in the air motor. While rated at 5 cfm, that is probably under absolute ideal conditions on a hand-built prototype saw. Make sure you use a good air tool oil, like Blaster, which will help with some of the losses. Generally, like a new auto motor, it takes a bit before the air blades in the motor 'wear in' and once that has occurred, it should reduce air consumption some. I would suggest a bigger tank, 20 gal isn't much at all when you are working with air tools.
Reply to
Anthony
What is the brand of your compressor? Does it include words such as "peak HP" or "maximum developed HP" somewhere on it? Usually, compressors are overrated, while air tools are underrated with respect to CFM. An easy solution may be to look for a used 80 gallon air tank. Some compressors have less efficient pumps than others.
I know that my 3 honest HP compressor is enough for all my air tools, including air hammers, orbital sanders, and a blow gun.
i
Reply to
Ignoramus27362
A bigger tank will only delay the inevitable. Once you draw the air reserve in the tank down to the point that the compressor kicks in, you're fighting a losing battle if the compressor is not able to pump air faster than the tool is consuming it.
- Michael
Reply to
DeepDiver
Do you have 90 or less PSI on the cutter ? or 125 maybe...
I can believe the tank falling from full to the low start compressor level - beading off air through the tool.
The compressor should be able to just make it to full but I suspect a leak or more pressure than 90...
Martin Martin Eastburn @ home at Lions' Lair with our computer lionslair at consolidated dot net NRA LOH, NRA Life NRA Second Amendment Task Force Charter Founder
Frank wrote:
Reply to
Martin H. Eastburn
My bet is it is not really 5 CFM! Many manufacturers are rating their tools at duty cycle, in other words maybe 25-30% of actual use. My bet is the tool uses close to 15 CFM continuous. A 2 HP compressor will not keep up with any air tool I am aware of! Trust me I had one for years! I upgraded to a compressor that produces about 10 CFM an it pretty much keeps up with all my tools. 15 CFM would be better, but I don't work that hard any way! Greg
Reply to
Greg O
"DeepDiver" wrote in news:FyB6f.428$ snipped-for-privacy@typhoon.sonic.net:
Yup, 100% agree, however, a larger tank will give you more run time between tank refills, so you can get a bit more work done before the saw quits.
Reply to
Anthony
Yes, but then you will also have to wait longer for the tank to come back up to full pressure. The bottom line is that compressor capacity is much more relevant than tank capacity when it comes to high-volume continuous operation.
- Michael
Reply to
DeepDiver
With that fairly decent compressor, you deserve a reasonable sized tank, say 40 gal+ Otherwise the compressor could be compressing air but not have anywhere to store it. The shop compressor we have is 208 v 3 ph 5+ hp sitting on a 200 gal tank, ~150 psi. Probably upwards of 30 CFM. Even with 2 people blasting away with die grinders continuously, it only turns on for about 30 sec every 5 minutes. The cut off tool like the one you describe does uses a fair bit of air (more than the die grinders), but we have had 2 people with impact guns simultaneously and it doesn't seem to need to catch ip.
Reply to
woodworker88
Hmmm. That just triggered an idea. If the tool is rated at 90 PSI and your compressor is supplying something significantly higher than that, a regulator will give you significantly more run time. Perhaps not enough, but more. I think I may try this myself.
Vaughn
Reply to
Vaughn
11 CFM seems to usually be enough for most single user "garage" shops in intermittent use. 7.7 CFM is not enough for most rotary air tools. I doubt that your compressor delivers 7.7 CFM once it gets hot, particularly if it is a single-stage unit. Further, with a small tank you'll be delivering hotter air to the tool. Hotter air at given pressure has less "poosh". Air tools are rated at cited pressure and flow with supply air at standard temp, probably 20C or so. Your air won't feel hot from a blowgun because it cools on expansion. Some rotary air tools get quite cold in operation when run from supply air at std temp.
A larger tank cools the air more between compression and delivery. It doesn't increase the capacity of the pump, but if the pump can keep up it delivers "better" air to the tool. As the air in the tank cools, pressure drops and the pump adds more air to maintain pressure.
For serious (e.g. professional) use, at least 15 CFM, >18 is bettter.
Reply to
Don Foreman

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.