Pneumatic impact wrench

ColinOConnell · **Posted:** Sun Apr 02, 2006 10:27 am

I've got an inexpensive air tool set and the impact wrench isn't loosening studs that I can get with a socket wrench and some effort. I'm using a light duty compressor ( 3 gal tank and 1.5HP motor ) that runs about 125psi. Is the problem likely to be the compressor capacity or the wrench. I had kina' hoped that it would handle a few short sessions and get the bolts lose.

Jason Mauldin · **Posted:** Sun Apr 02, 2006 10:28 am

It's most likely the impact wrench

Scott Johnson · **Posted:** Sun Apr 02, 2006 3:09 pm

Inexpensive air tools = teh suck.

David Teague · **Posted:** Sun Apr 02, 2006 4:24 pm

Its the Impact Wrenmch, I could not get the crank bolt off my integra when changing the timing belt, so I borrowed the Westerfields Snap On and it came right of, The tools I had cane with the air compressor.

ColinOConnell · **Posted:** Sun Apr 02, 2006 10:18 pm

Thanks, kinda what I thought. You usually get what you pay for. The transmission came off without too much hassle today, would have been easier with a good impact wrench. Clutch and flywheel are in and the transmission's back on. About 10 hours so far, just torquing some things and reinstalling the drive shaft and exhaust parts and we'll be starting the bushings and coilovers.

Adam Ligon · **Posted:** Sun Apr 02, 2006 10:24 pm

Well why it might also be the impact gun, that compressor is defintly too small for any impact guns' cfm needs. It will run the gun but it won;t let it reach its peak torque

Charlie Smith · **Posted:** Sun Apr 02, 2006 11:12 pm

David Teague wrote:

Its the Impact Wrenmch, I could not get the crank bolt off my integra when changing the timing belt, so I borrowed the Westerfields Snap On and it came right of, The tools I had cane with the air compressor.

What was the torque rating on that Snap On? Just curious because I had the same problem when I did my Integra's timing belt. I ended up borrowing a massive impact from a mechanic friend to get it off.

Charlie Smith · **Posted:** Sun Apr 02, 2006 11:15 pm

Adam Ligon wrote:

Well why it might also be the impact gun, that compressor is defintly too small for any impact guns' cfm needs. It will run the gun but it won;t let it reach its peak torque

Are you sure about that? I agree that the tank can't provide the max torque once the pressure drops below the regulator setting (90 psi probably). However, it will provide the same CFM (torque) as a tank 20 times that size until that point. The only problem with the small tank is that the pressure will drop much faster.

Charlie

Wes Eargle · **Joined:** Mon Oct 27, 2003 9:47 am **Posts:** 3683

The compressor motor for a tank that's the capacity of a case and a half of beer will be on all of the time with any air tool other than a nailer.

ColinOConnell · **Posted:** Mon Apr 03, 2006 9:56 am

Yeah, we'd run it for a few seconds and if it had the torque to losten the nut then it would be able run it out. The compressor motor would come on a few seconds after we started the wrench, so I couldn't sit there and let it bang on the bolt for too long and I'd still have to wait to start on the next nut. Anyway, it made the job easier but the right combination here would probably have made it a lot easier.

Adam Ligon · **Posted:** Mon Apr 03, 2006 9:58 am

Charlie Smith wrote:

Are you sure about that? I agree that the tank can't provide the max torque once the pressure drops below the regulator setting (90 psi probably). However, it will provide the same CFM (torque) as a tank 20 times that size until that point. The only problem with the small tank is that the pressure will drop much faster.

Charlie

For the compressor size he listed yes, it would not provide the min cfm needed.

A quick search of both impact guns and compressors that size show that the least cfm requirement for an impact gun is 5cfm @90psi with some better more powerful guns needing 7-9cfm. While compressors of his size, and some bigger, average providing 2-3cfm @90psi.

ChuckNelson · **Posted:** Tue Apr 04, 2006 12:11 am

Should you decide to get a new gun or bigger tank.
Get an Ingersol Rand. I have Mac and SnapOn Impacts and they just can't match the Ingersols I used. They are also super tough
If you are going to do much get a compressor that has a piston pump. The airless pumps may not need maintainence but they can't keep up with high cfm tools, like drills and die grinders. (I learned this the hard way) They are also LOUD. I have a big oiless(50gal) and it will lag behind a die grinder so fast you hafe to stop every 30 seconds to let the pres build back up. It is in a box in the garage with two layers of carpet for sound insulation and you can still hear it on the other side of the house.

Charlie Smith · **Posted:** Mon Apr 10, 2006 11:21 pm

Adam Ligon wrote:

Charlie Smith wrote:

Are you sure about that? I agree that the tank can't provide the max torque once the pressure drops below the regulator setting (90 psi probably). However, it will provide the same CFM (torque) as a tank 20 times that size until that point. The only problem with the small tank is that the pressure will drop much faster.

Charlie

For the compressor size he listed yes, it would not provide the min cfm needed.

A quick search of both impact guns and compressors that size show that the least cfm requirement for an impact gun is 5cfm @90psi with some better more powerful guns needing 7-9cfm. While compressors of his size, and some bigger, average providing 2-3cfm @90psi.

Actually, what I said is still an accurate statement. The CFM rating is the amount of air that the COMPRESSOR can deliver. Therefore, the same amount of air is being delivered to the tool for a 2 gal tank at 120 psi as a 200 gal tank at 120 psi (until the pressure drops lower faster on the smaller tank).

Charlie

ColinOConnell · **Posted:** Mon Apr 10, 2006 11:47 pm

yeah, but the cheap little POS isn't hangin' in there. I thought (hoped) that it was dieing tonight so I could (need) a new one. It's been working it's butt off on the current bushing/shocks/springs project and, like the idiot at work that we all know, it doesn't matter how hard it works it isn't going to get done without help. In this case it's a breaker bar or rubber mallet. Once the nut is lose, the air tools speed up the removal process.
After my first term of use with air tools I'll agree that the compressor is insufficient and probably 80% of my problem. It's rated at around 2.5 SCFM at 90 psi and it seems that the OIPM for the impact wrench shows that it needs 4 SCFM. I think the rating on the air compressor has to do with the regulator which would be sized for the unit because, you are right, until tank pressure fell below 90 psi it should provide the same pressure and CFM at the gun regardless of the tank size. It was purchased for use with an airbrush (artwork not car painting) so I can't blame it for not holding up under current demands.

Thanks for all of the input

Adam Ligon · **Posted:** Tue Apr 11, 2006 8:45 am

Charlie Smith wrote:

Actually, what I said is still an accurate statement. The CFM rating is the amount of air that the COMPRESSOR can deliver. Therefore, the same amount of air is being delivered to the tool for a 2 gal tank at 120 psi as a 200 gal tank at 120 psi (until the pressure drops lower faster on the smaller tank).

Charlie

Um no, thats not right. The pressure of the air may be the same for a moment, but the amount/volume of the air is vastly different between those two compressors.

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