Minimum DIY air compressor for home

[JHZR2]

Hi,

I am curious what is the minimum air compressor I can use for small DIY jobs. I would never be sandblasting, never be painting, etc., etc. I would have an impact ratchet and a gun, so that I could remove bolts that hold brake calipers and lug nuts. Thats really about it.

I may be way off, but I wouldnt mind only being able to use the tool for a couple seconds at a time... it still would be a LOT better in many situations that I encounter, than a breaker bar or whatnot.

Space is a premium, so thats why Id like as small as possible. I also wouldnt want to spend that much $$$, as I wouldnt use it THAT much, or for that many things.

We just got a 1hp thomas at work for some lab uses... its electric, 1.7 CFM at 100 psi, and has a 2 gal tank. Its a nice size... but it might be too small to even start the tools... I couldnt say as I have NO experience. It would be about optimal in size, etc for me.

I wouldnt mind a gasoline powered unit, as I like/prefer things with engines over motors... but that would likely make it more $$$. However, opinions and infor would be appreciated.

So many of the topics on the board that I searched had much larger uses than I desired. Many reccomended much larger units than I could take and keep. All I want to do is run an impact wrench or ratchet unit for a few seconds at a time. Just enough to loosen nuts/bolts. Beyond that I dont mind even using an old fashioned ratchet...

Any insight would be appreciated.

Thanks,

JMH

 

[stringsattached]

Most air-driven impact wrenches that are going to have enough torque to break a lug nut loose are going to require a compressor of a pretty decent size/price tag.

Have you considered an electric impact wrench? The Lowes & Home Depot around here carry models by Dewalt, Milwaukee, etc. in the $150.00 - $200.00 range, but I've never had any personal experience with using an electric one, so I couldn't tell you any pros/cons.

Lug nuts are on there pretty tight, so if your main goal is to get those off without breaking a sweat; you're probably going to pay for it no matter which route you go. For general use though, I should think any good quality brand would do fine if you weren't buying the cheapest one they made.

And never underestimate the power of low-tech tools and/or renting!

 

[JHZR2]

I am actually thinking maybe of getting one of these:

http://www.powertank.com/start.htm

Its all passive, so its quiet, has more capacity than Ill need, and can run anything.

Of course Im sitting on a pressurized vessel then, which may not be optimal.. though it is more or less a fire extinguisher, which is safely put everywhere...

But if I am to get an electric one... Say I buy a small one, say 5 gallons. Say it is rated for 2.4 scfm @ 90 PSI, and say I want to run an impact wrench at 4.8 scfm @ 90 psi... Does the fact that I have a reservoir tank allow me to run the tool ONLY until the reservoir drops below 90 psi, then it will die out?

Say my compressor is rated at 4.8 scfm, as is my tool, then I could run it indefinitely, right?

Im sure its simple, but I am not entirely sure of the conversion between scfm, psi, and reservoir volume.

Thanks,
JMH

 

[eljefino]

Don't get the co2 thing, you'll have to pay someone to refill it.

If you have a harbor freight or big lots near you check out what you can get for $100, you might be suprised.

Your example of a 2.4 cfm compressor running a 4.8cfm tool would need 50% tool rest time with the compressor running continuously. Most regulators stop at ~115PSI and tools need around 90 so simply wait until the compressor shuts off from filling the tank then hit that lugnut. If the tool's performance slacks off let the compressor recharge. In other words the compressor will go over 90 psi just more slowly; they're rated at 90 psi because that's what many tools take.

A bigger tank will lessen the times the compressor cycles on and off, an annoyance. And, for example, you could zip off all your lug nuts at once then the compressor will recharge while you're moving your wheels around.

People will tell you "don't get that cheezy thing buy a huge one from sears it will last you a lifetime." But if you have to spend forever saving up for it you won't enjoy air tools. And used compressors hold their value quite well so you can upgrade if you ever need to.

 

[stringsattached]

Looks cool, but on the "Online Store" page, the cheapest one I'm seeing is $430.00 Am I missing something?

 

[stringsattached]

http://www.sawdustmaking.com/AirCompressors/air_compressor.htm
http://www.northerntool.com/catalog/buyersguides/aircompressors/

 

[JHZR2]

Yeah, theyre pricey... but one fill goes a LONG way because of the storage pressures.

JMH

 

[JHZR2]

OK, here's what Im thinking... correct me please if Im way off...

THe #1 use Ill have for an air compresor setup is getting lugnuts off. The #2 use Ill have is for saving time doing ratcheting.

I am interested in an oiled Makita compressor (the exact one as in the top right side of the sawdustmaking link given above... or its bigger brother the dual-tank unit). It has full size motor and compresor, runs slow, and is cast iron. It has a small tank (2.6 or 4.2 gal), so its nice and portable.

If I go by the fact that p1*v1=p2*v2, then solving around with the specs from Makita...

130 psig (cutoff)* 2.6 gal (tank size) / 90 psig (tool operating) = 0.502ft^3

So, In using a tool from a unit that has 2.6 gal of air stored at 130 psi, I have 0.5 ft^3 of air volume from which to extract work with a tool using 90 psi air.

Now, if I have a tool that uses 5 cfm @ 90 psi, then I can do work for 0.1 minutes, or 6 seconds, right???

So in other words, I could run my impact wrench for 6 seconds before the motor turns back on, right?

This would be A-OK for me, as Id only be doing one lugnut at a time, then removing it, putting it in another spot, etc. I will be working in my driveway, so its not like I can work very fast regardless.

Now, if in a little while, I decide that I'd like a little more staying power, and am willing to wait a bit longer for the tank to recharge, then I could plumb in a second tank, right?

I feel that Id never be in such an operational tempo that Id be constrained by the tank refilling (the makita units supposedly fill very fast anyhow), and Id likely never need anything much bigger, especially if I add a external second tank for the extended jobs (if needs be).

Am I way off? I really like the makita unit, and at just over $150, it seems like a steal - I could then spend more on the gun and ratchet, and get good IR ones or similar.

Thanks,

JMH

 

[stringsattached]

The Makita one only kicks out 3.3 CFM @ 90 psi though; in my understanding you need a compressor than can flow 4-5 CFM for the type of impact wrench you are talking about. A tool that requires 5 CFM @ xxx psi will just flat out not work right at anything below that. A 3.3 CFM @ 90psi compressor shouldn't be able to run a tool that requires 5 CFM @ 90psi correctly. The only variable in the amount of time your tool will run is the tank size and the duty cycle.

Then again, look who's talking.

This might be a job for the support hotline at Porter Cable! (ask them about the electric IW's too, while you're at it)

[ January 27, 2006, 01:25 AM: Message edited by: stringsattached ]

 

[stringsattached]

Ok, more Googleing. Coleman and Lowes both advise that you actually buy a compressor that can put out a little than more what your biggest tool requires. (For Coleman, it's at the bottom of the page, for Lowes, it's under "Other Considerations".)

http://www.lowes.com/lowes/lkn?action=howTo&p=BuyGuide/ChsAirCompressor.html#2

http://www.colemanpowermate.com/compressors/comparingcompressors.shtml

But I don't know if you want to believe them either though, because they are the ones trying to sell them to you! Ahhhhh! Where is a good air compressor scientist when you need one?

 

[JHZR2]

lol, I know... Thanks for all the help though, I really appreciate it!

My best source of info has been the RV and 4wd guys, who need to carry a small compressor and tank, as they dont have space for anything else...

A good example is here:

quote:

---

With my Thomas compressor and a 1/2" drive, 350 ft.lb. impact wrench and a 2 gal. (1/4 cu.ft.) air tank, I found I could remove 1 wheel lug nut in about 5-7 seconds of run time. The impact wrench is rated at 4 CFM the compressor about 1 CFM@90 and it took perhaps 20 seconds or so for the compressor to shut off at the 100 PSI limit. In this application, I did have to wait for the tank pressure to rise, to ensure maximum torque was available for breaking the next lug nut loose. I probably need (and plan on adding) more air storage in my system and some extra pumping capacity probably wouldn't hurt either. On the other hand, my shop compressor can usually remove all 6 lug nuts from a wheel in one cycle, although available torque drops as the tank pressure falls.

---

This is promising to me, and inline with my calculations above as far as runtime goes with a small tank...

Thanks,

JMH

 

[road_rascal]

I'm thinking about getting one of these for my garage:
http://www.sears.com/sr/javasr/product.do?BV_UseBVCookie=Yes&vertical=TOOL&pid=00916732000

 

[Todd_96SRV]

I've got a 2hp, 6 gallon model & it does the job... I use a 1/2" impact gun on all types of bolts & a 3/8" air ratchet without much trouble. The compressor cycles frequently, but I've never really had a lack of torque as result of a small compressor...

 

[porcupine73]

A couple ideas/comments: When I first started using air tools, I used 1/4" QC's and 3/8"id hose on everything. I noticed the IR impact wrench didn't seem to have much power. I switched to 1/2"id hose and 3/8" QC's and that made a huge night and day difference, I'd say the 3/8" QC's more so than the 1/2"id hose.

Also note that at any given flow you will have pressure drop across the fittings/hose, so to run a 80psi air tool you really need more pressure than that at the compressor.

My compressor is rated I think 4.8SCFM at 90psi. Sometimes if I'm doing a lot of air tool work, I tee in one of those portable 10 gallon air tanks in the line. It gives me a little more reserve capacity so I can run continuously longer until the pressure drops so much that I have to stop and let the compressor recharge the tanks.

Also harbor freight sometimes has really good sales on filter/regulator/lubricator units.

-Louis

 

[JHZR2]

thanks all for the insight!

JMH

 

[nel]

I have a small Emglo (now DeWalt) compressor. It's similar to the Makita unit you were talking about--two small tanks, 110V, oil-lubed. I've used it along with my 1/2" IR impact wrench for suspension work without any problems, as well using it with an air hammer.

The only issue I've had with it has been running an old Snap-On 3/8" ratchet and my die grinder. I could probably buy a more efficient air ratchet, but I would probably need a larger compressor if I want to use die grinders and other high cfm-demanding devices.

BTW, I've found the IR tools to be fairly cfm-efficient.