Air Compressor/air tool combination question

[08Silverado]

Hello all,

Just received an 8 gallon kobalt air compressor for my birthday (4cfm@ 90psi) max psi 125 I believe.

I am trying to figure out what tools are capable to run off this... I know that grinders, sanders and paint guns will not work with this compressor.

But what about an IR 1/2 impact rated at 4.2cfms? Or a 3/8Dr socket ratchet wrench?

I have read/watched tons on this question, but haven't found a definitive answer.

Would adding a second air tank (10 gallon) to the system work better? Would adding a larger hose help deliver more air to the impact wrench? Or am I basically SOL with this combination?

I will be using these tools while I rebuild my k5 blazers front suspension, so I will need something with some oomph to break rusty nuts/bolts this summer. (Thanks to Michigan winters)

thanks,

John

 

[OHMS LAW]

For home diy it will suit just fine. May have to take a few breaks but I've worked with smaller. I used to use a small compressor my dad used in the 80s for framing houses. It was 5 gal 1/2 hp. Lol it did what I needed to do then.

 

[08Silverado]

You don't think the compressor being at 4.0cfm and the impact wrench being at 4.2cfm won't be a problem?

 

[OHMS LAW]

If you were trying to run a whole shop with that yes it would be a prob. But since it's just you and a smal length of hose I wouldn't even think twice about it

 

[08Silverado]

Awesome, Thank you for the input.

 

[sberry]

You can try it but,,,,,,,,, the impact uses about 15cfm.

 

[AndyA]

You can try it but,,,,,,,,, the impact uses about 15cfm.

Yeah, but you also only use it for 3 or 4 seconds (unless you have something really stubborn). You may have to wait a little bit in between each lugnut to let the pressure build.

I've changed tires/wheel on the side of the road on the 5 ton truck using a 3/4" impact and nothing but the on-board air. I sometimes had to wait and take several attempts on one lug. Still beats taking them off by hand, or walking home.

 

[Scimmia]

Small tank means shorter running time. Low(ish) output means it takes longer to refill. Should work fine, will just take longer to get things done.

 

[08Silverado]

So would adding a second tank be a pretty good idea? I know that the pump would make longer to fill and that the duty cycle would become an issue, but would more air = more use of the wrench?

Thanks all for the helpful advice.

John

 

[chris142]

I feel that the impact won't put out full power. Adding a bigger tank would help. I wonder if a longer hose would help store some extra air?

 

[Heavymetalmechanic]

I was in the same situation before I rebuilt my 30G Quincy 214. Mine was a 8G 3.5cfm@90psi. I converted a 50lbs propane tank into a tank I could throw in my truck to fill tires. With the spare tank hooked up to it (in parallel, NOT series) I could remove a tire with a 1/2" impact without waiting for it to recharge. Big thing to check is the duty cycle of the compressor, the run time to fill both the compressor and second tank was right at the upper limit of my duty cycle (oiled direct drive, reed valve, single piston, Mastercraft). I changed the oil in it regularly, it is still going strong as my framing compressor.

The problem with compressors is that it will NEVER be big enough...

 

[Scimmia]

So would adding a second tank be a pretty good idea? I know that the pump would make longer to fill and that the duty cycle would become an issue, but would more air = more use of the wrench?

Thanks all for the helpful advice.

John

The following numbers aren't based on anything real. They're to demonstrate a point only.

Right now, you're at the point of using the tool for 20 seconds, then waiting a minute for the tank to refill. Adding a second tank of the same size would mean running for 40 seconds, then waiting 2 minutes to refill. Is this better? Depends on your usage.

 

[08Silverado]

The following numbers aren't based on anything real. They're to demonstrate a point only.

Right now, you're at the point of using the tool for 20 seconds, then waiting a minute for the tank to refill. Adding a second tank of the same size would mean running for 40 seconds, then waiting 2 minutes to refill. Is this better? Depends on your usage.

This makes sense... it mainly would be for breaking stubborn bolts loose, pulling lugs off[if possible] and just odds and ends when it's convenient [such as filing tires]. If the tool is used intermittently, like say 3-4 second bursts with a 2-3 second rest, will the compressor still struggle to keep up?

I Have a 50ft air hose that came with the compressor. Does hose length help/hinder air tool usage?

Thank you for the continued replies.

John

 

[Scimmia]

If the tool is used intermittently, like say 3-4 second bursts with a 2-3 second rest, will the compressor still struggle to keep up?

Yes. Most of the 1/2" IR impact specs I've seen say that they use 20-25 CFM while running. If the compressor can put out 4CFM, that means you'll need to average 4-5 seconds of down time for every second of run time.

I Have a 50ft air hose that came with the compressor. Does hose length help/hinder air tool usage?

Thank you for the continued replies.

John

Hose length hurts. The longer the hose, the more restriction it has, so you have to maintain a higher pressure off the regulator to make up for it. With a 125 PSI max compressor and a 50 foot hose, you may be best off just removing the regulator all together as long as you aren't using a tool that needs a consistent pressure such as a paint gun or a nail gun.

 

[ZRH`]

I Have a 50ft air hose that came with the compressor. Does hose length help/hinder air tool usage?

Thank you for the continued replies.

John

Hinder. Air hose causes flow rate drop because of the friction/turbulence of the air moving along the hose. That's why shop air systems are usually metal tubes with rubber drops, there is less friction/turns in a metal line.

It's still better to run more hose than it is to run more extension cord though, you can't "hurt" most air tools by running more hose, they just wont work. You can burn out the compressor motor with the voltage drop in an extension cord though.

 

[redmondjp]

An additional tank would help.

 

[08Silverado]

Ok. This has given me something to think about.

Based on logic, a shorter, wider hose would be a decent idea for my set up?

I just double checked my compressor, it's 150 max psi, sorry for the misinformation.

Again, thank you Scimmia, and everyone else for the information.

John

 

[Scimmia]

150 PSI helps the situation considerably. You get to put more air into the tank, effectively making the tank act larger.

A shorter, wider hose helps flow and will allow the tool to keep working for a little while longer as the tank depletes, but it doesn't change the basic relationship between tool consumption and pump output.

 

[08Silverado]

Ok. I understand now. Thank you very much

John

 

[sberry]

These little comps could benefit from shorter hoses. There just isn't the head room to turn them up. Bigger systems with more poop behind them are more forgiving. A regulator doesn't bother me much but I agree as soon as one pulls the trigger on a little unit are dropping below the curve anyway.

 

[sberry]

Even big tank bigger pump single stage units we see here don't need a reg for impact use and only deliver full power when they are fully pumped up. With 2 stage the kick on pressure is at about this point.
This is where size means a lot when sanding etc, if the pump is greater than the demand you never notice a lag, if not it needs a break in use between kick on and before kick off to maintain adequate flow.

 

[sberry]

I have 2 comps put use 1. I use the tanks of both. My main is 3 hp and my backup/demand is real. The breaker is off to unit 2 unless needed which is about zilch. As an operator I can time a unit to keep it running continuous, I fill my gun, move my setup, change tool etc. Do all my chores and resume just before cut off and the pump is running and tank pressures are 160-165 ideally. Even if you start when system pressure is down it takes but a bit to build up.
I been doing it long enough I have a sense of its this pump I am running and where and how long before it turns on or off. Running a bitty die grinder short times, most of the time the system is pumped up, doesn't make much difference, only in sandblast and some sanding operations is there true demand for air in a small shop.
I am fairly extensive and live on 3 hp and 200 gallons of tank and can sand with 7 inch at about 25 minutes out of 30.
When you have poor air a reg may help and choke to give a little longer run times.
I would look at new 3/8 impact that used about half the air. New battery power is about the best.

 

[08Silverado]

Would a 3/8 impact be able to get lug nuts off? Would it be better to get a 3/8 impact with a 1/2 adapter and a set of 1/2 impact sockets?

Thanks,

John

 

[ZRH`]

You can get lug nuts off with a breaker bar if you are properly motivated

About your compressor though:
http://www.lowes.com/pd_470442-3044...y_sales_dollar|1&page=1&facetInfo=Kobalt#noop

Is this the compressor you have?

It does 5CFM at 40 psi and the cut in is 120 PSI. A secondary tank might help but it looks like enough (just enough) to run a half inch impact wrench.

 

[08Silverado]

Yes, that is the one. But the tool I'm looking at [Ingersoll Rand 231C] operates at 90 psi.... or is that the max It can work at? It's either I get the 231c or the 2115Ti 3/8 ingersoll rand.

As for the breaker bar I have a real solid 3/8th and 1/2 breaker bar, but I am looking for something simpler. If my compressor isn't capable of breaking lug nuts, I will still use my breaker bars.

John

 

[ZRH`]

No 90 psi is the min. You can run it up to infinity for more torque (and breakage).

I just looked at the 1/2 wrench you are thinking about getting. I remember those wrenches. You will have to wait for it to refill after every bolt. I started with a 20gal 2 hp compressor.

It's not too bad, I mean it was a gift after all and an air impact is cheap compared to buying an electric impact wrench.

 

[sberry]

90# at the gun while operating, way different than 90 at the tank.

 

[08Silverado]

Gotcha. So if I were to buy a 10 gallon husky air tank, with a 1/2 impact I would be better off than if I just got the impact wrench?

The 3/8 2115ti is slightly less powerful, but all the reviews I have read indicate that lug nuts and rusty bolts aren't a problem. It also has a 4.0cfm/avg, as opposed to the 1/2 which is 4.2... is this not even a major difference at all?

There are cheaper 3/8 impacts out there that average 2.5-3.0cfm/avg but I feel as if the power wouldn't be there at all.

Thanks,

John

 

[Loscaldazar]

For intermittent use tools like an impact wrench, CFM is almost irrelevant. CFM of the pump only indicates how fast the pump can fill the tank.

PSI, not CFM is what determines the power of the gun. A 150 PSI and 0.5 CFM compressor will result in more power from an impact gun than a 90 PSI and 10 CFM compressor (assuming no regulator).

Like I said, CFM is only important when the tank is empty/drained below the required PSI needed to power an impact. With intermittent use tools, there is time to recharge the tank between uses. For example, let's say your 1/2 impact can remove 4 of your 5 lug nuts before dropping below the cut in PSI of the pump (the pressure that the pump turns back on for). You remove 4 lugs, then wait probably just a few second until you have enough PSI to remove that last lug nut. You set the impact down, take off the wheel and then set the wheel down. You go back and pick up the impact and walk over to the next wheel. While you were doing all that, your low CFM compressor has probably already built itself up to max pressure or pretty close there. You can now remove 4 more lugs, wait a bit, then remove the fifth, and take off the wheel/mess around and then repeat the above for the remaining wheels.

You still have a fully powered gun through all this, you just might have to wait at times for the PSI to build back up. By no means a bad thing for an at home compressor (bad idea in a shop when time is often critical though).

When CFM is important is when you drain the tank below the required PSI you need to power your tool and you still need to use the tool and can't stop to let it recharge. This isn't a problem for impacts (you can always stop whenever you need to), but for paint guns it is a HUGE problem. If you have to stop and wait for your tank to recharge, or PSI keeps dropping below what you need, you will have problems with your paint coats. That is a case where you need a very high CFM pump because you WILL drain the tank and WILL have to run your paint gun "directly off the pump output."

So, having the appropriate PSI is way more important for an impact than having a pump with a CFM rating that could run your impact gun continuously.

Also, note, in reality the PSI at the tank, or after the regulator if you have one, always needs to be a little higher than what you want at the gun. Friction drops the PSI, and the longer the hose/piping length, the more PSI drop you get. Just something to be aware of.

 

[08Silverado]

Thank you for the excellent read, Loscaldazar, this really puts things into perspective.

Based on the information you presented, it sounds like I will be good in terms of intermittent tool use on both an impact and air ratchet, but for extended use my tank will run out pretty quickly.

I will definitely be investing in a shorter hose, probably 25ft as opposed to the supplied 50ft hose the compressor came with.

I do not mind downtime while wrenching, it gives me time to think or organize my parts/tools.

When you say the tank will refill, does this mean the compressor will kick on? Or will it only turn back on if I run it below a specific number? I assuming this function is controlled by the regulator, that when it goes below a selected psi the compressor turns back on to fill the tank? What if the regulator dips to a number that is above where the regulator is set, will it slowly refill the tank, or does that only happen when the psi falls below the specified number?

I apologize for the all the questions, I am just trying to familiarize myself with this new system. I've never used air tools, so I am pretty excited to learn and use them.

John

 

[Loscaldazar]

No worries on the questions. I was were you were once (only a few months ago!), so I understand how much there is to learn.

The pump will only kick on and refill the tank when the tank drops below a certain PSI. I believe someone else said that your compressor will kick on when tank PSI drops below 120 PSI (can't confirm, but I'm going to assume they are correct). If the tank PSI does not drop below 120 PSI, it will not start pumping until the tank PSI does fall below 120. So you may run into a situation where you remove 1 lug nut, and then have to wait for the compressor to refill to a high enough PSI to remove the rest of the lugs. If you are paying attention, you might be able to run the gun under no load for a few seconds to drop the PSI below 120 and let the tank refill while you are removing the wheel or doing other things. The function is actually probably controlled by a pressure switch and is separate from the regulator.

Your compressor looks like it comes with a built in regulator. Once again, I'm not exactly sure the way your compressor works, but my guess is that the regulator only lets you control the PSI output from about 0 to 120 (125?) PSI. Adjusting the regulator up or down should not impact the PSI at which the pump kicks on and fills the tank.

 

[08Silverado]

Makes sense. So when the regulator is at 110 psi, I use the tool, and it drops to let's say 100psi, it will not float back up at all, it will only refill after the psi to kick the compressor back on is reached?