Air Impact Wrench vs Clarke Electric Wrench

[ukkid35]

I have been using a Clarke CEW1000 rated at 450Nm for several years but it won't remove seized wheel nuts on my Smart

So I've just used this an excuse to buy a compressor and a Rotake RT-5278 rated at 880Nm

The compressor is the Aldi Workzone branded unit which seems a bargain at just £70 delivered

As this is for occasional use only I am manually oiling the wrench rather than fitting filters

The problem is that the Rotake is clearly delivering much less power than the Clarke, and isn't making any impression on the seized nuts

Here are the specs, what am I doing wrong?

Wrench
Max. torque: 650 ft. lb. (880nm)
Wrench Weight: 3 kg
Regulation left / right with a three-way power adjust
Working pressure: 90 PSI (6.2 bar)
Air consumption: 8 CFM 230 [l/min]

Compressor
2.5HP
24LTR
8 BAR
9.3 CFM

Hose
Seally 8mm x 5m

Edited by ukkid35 on Friday 14th June 08:27

[PHuzzy]

Your compressor will be rated at SCFM, which is far less than the amount needed to run the tool.

[ukkid35]

PHuzzy said:

Your compressor will be rated at SCFM, which is far less than the amount needed to run the tool.

Oh great - so the 9.3 CFM quoted for the compressor is effectively meaningless?

[PHuzzy]

ukkid35 said:

PHuzzy said:

Your compressor will be rated at SCFM, which is far less than the amount needed to run the tool.

Oh great - so the 9.3 CFM quoted for the compressor is effectively meaningless?

Effectively yes, it happens with all compressors too
They measure the inlet flow of the compressor at atmospheric pressure to give SCFM instead of outlet flow at a given pressure which is your actual CFM.
It's advertising/marketing bullst.

You can calculate the actual CFM of it but it's far too early for math.

My rule of thumb is usually to divide claimed CFM by 6 to get actual CFM. It's not spot on but it should be close enough.

Edit to add, by all compressors I mean commercial ones. Industrial compressors are rated at delivered CFM not the stty SCFM.

Edited by PHuzzy on Friday 14th June 08:46

[Peanut Gallery]

Is there a regulator between the tank and the air gun? - Any other restrictions in the line?

Regarding the air available from the compressor - in cubic feet per min, if the tank is full, and you go for a quick blast with the driver, this uses the air stored in the tank, rather than the speed at which the compressor can re-fill the tank?

If you are doing a long job of painting, then yes, the compressor has to deliver more air than the tool you are using, however if you are whizzing wheel nuts off, it would take its sweet time to load the tank, you undo one nut, it recharges the tank while you mutter and go looking for the locking wheel nut you left on the wheel last time you changed the wheel 2 years ago or something.

[ukkid35]

PHuzzy said:

My rule of thumb is usually to divide claimed CFM by 6 to get actual CFM. It's not spot on but it should be close enough.

Disappointing

[ukkid35]

Peanut Gallery said:

Regarding the air available from the compressor - in cubic feet per min, if the tank is full, and you go for a quick blast with the driver, this uses the air stored in the tank, rather than the speed at which the compressor can re-fill the tank?

That is exactly what I had assumed

[PHuzzy]

I did the rough calculations and posted it but the formatting was all screwed up.

The calculations show a rough actual CFM of 1.3 for your compressor when using that tool.

A bigger (much much bigger) tank is the only way to get most 'cheap' compressors to be of any real use for domestic/hobby use.
I gave up on air tools a long time ago and have moved to plug in/battery tools now.

Edit to add, handily works out for my rule of thumb.

8CFM/1.3CFM = 6.15

Edited by PHuzzy on Friday 14th June 09:23

[paintman]

Common issue.
Smaller compressors are usually listed as air displaced, not free air delivered which makes them look much more capable than they really are.
AFAIAC it's a con.
Sometimes the passageways to the air outlets on them are very small & this doesn't help either.

To work at full capacity your wrench needs 230l/min maintained at 90psi which is a LOT of air. This is 3 phase compressor territory & small compressors are incapable of that. Yours will give you a couple of seconds full power from the air in the tank at very best & that's not going to do much.

I have a similar sized compressor & stuff such as air sanders, air DA sanders, grinders, sandblasters etc are non-starters. Great for blowing air to clean stuff, inflating tyres & will run SMART repair sized HVLP gravity feed guns. It will do a full size HVLP gravity feed spraygun but it's really at it's limit.

You would be better buying a breaker bar to start your nuts & then just use the wrench to spin them off.

[ukkid35]

paintman said:

Yours will give you a couple of seconds full power from the air in the tank at very best & that's not going to do much.

Sadly not, the power (or lack of it) is constant from the start, and the wrench will run for 3 or 4 seconds before the compressor restarts

paintman said:

You would be better buying a breaker bar to start your nuts & then just use the wrench to spin them off.

Unfortunately that is how I snapped the head off one of the other bolts, which I am in the process of drilling out, which ain't easy either

[ukkid35]

PHuzzy said:

The calculations show a rough actual CFM of 1.3 for your compressor when using that tool.

Many thanks - at least it was only £70, no wonder it was sold as 'New Other - Customer Return'

Hopefully it will still be useful for an air-ratchet, where space might be a limitation otherwise

I've also bought an air chisel after a friend showed me how handy it was for removing bushes

[227bhp]

ukkid35 said:

paintman said:

Yours will give you a couple of seconds full power from the air in the tank at very best & that's not going to do much.

Sadly not, the power (or lack of it) is constant from the start, and the wrench will run for 3 or 4 seconds before the compressor restarts

paintman said:

You would be better buying a breaker bar to start your nuts & then just use the wrench to spin them off.

Unfortunately that is how I snapped the head off one of the other bolts, which I am in the process of drilling out, which ain't easy either

You snapped wheel bolts off?
An impact wrench doesn't circumnavigate the laws of physics, you'll still snap bolts off, it'll just make it easier to do so.

[ukkid35]

227bhp said:

You snapped wheel bolts off?
An impact wrench doesn't circumnavigate the laws of physics, you'll still snap bolts off, it'll just make it easier to do so.

Sorry, I have to disagree

The force applied by a breaker bar is entirely different to the force applied by a rotary wrench

People regularly snap seized bleed nipples off calipers because they insist on using spanners or ratchets, but you can remove most seized bleed nipples if you use a socket on a T-bar



The fact that I ignored this when desperately trying to remove the wheel bolts has cost me dearly

[Nimby]

ukkid35 said:

Oh great - so the 9.3 CFM quoted for the compressor is effectively meaningless?

AvE was "slightly miffed" by this recently: https://www.youtube.com/watch?v=cfjSm_ieRkE . Audio NSFW

[Coilspring]

ukkid35 said:

Sorry, I have to disagree

The force applied by a breaker bar is entirely different to the force applied by a rotary wrench

People regularly snap seized bleed nipples off calipers because they insist on using spanners or ratchets, but you can remove most seized bleed nipples if you use a socket on a T-bar



The fact that I ignored this when desperately trying to remove the wheel bolts has cost me dearly

You can also undo overtight wheel bolts with a breaker bar without breaking them too.

Any impact gun increases the risk of breaking any fixing. Way easier to break a wheel bolt with a good gun than it is with a breaker bar.

[227bhp]

So on that note I should be using an impact wrench to undo bleed nipples then? Ok.

[ukkid35]

Nimby said:

AvE was "slightly miffed" by this recently: https://www.youtube.com/watch?v=cfjSm_ieRkE . Audio NSFW

Many thanks - that should be required watching for anyone even considering buying air tools

[ukkid35]

Kobalt are now quoting a useful CFM figure for their compressors, but they are a US brand

Sadly the EU has been rather slow off the mark at regulating compressor ratings for consumers

[wildoliver]

Pretty much as above, compressor far too small to be much use for anything other than light work like blowing up tyres. And sadly the impact gun isn't the best make in the world and possibly won't do what it says on the tin even when it does have a proper air supply. Looks like they copy old Chicago Pneumatics designs (excellent by the way). It might be fine but I'd rather a decent used quality item than a new Chinese tool.

Must admit though as a regular dismantled of rusty cars I do slightly disagree with the assumption a breaker bar is gentler on a bolt that wants to snap than an impact gun. The action of the impact rattles can often free a stuck bolt off in the same way as a sharp smack on the end of it with a hammer pre loosening will, where as a breaker bar just provides a steady stream of force allowing the seized section to stay seized while you twist the head off. Quite often a seized bolt is just going to break pretty much whatever you do but heat resolves most issues ime. About the only advantage hand tools do have is where the fastener starts to turn but then locks up on some rust, allowing you to work it back and forth to clean the thread with some lubricant and work it out in one piece.

[eltax91]

Had similar issues in the past, small compressor, numbers fools me. About 5 years ago I ended up with a large 200L Clarke compressor and an ingersol rand gun and its never failed to undo anything.

That said, 5 years on and battery technology has changed so much that impact wrenches with the lithium ion battery’s get silly power these days, and there’s no air hose pissing you off in the way and you can take it further than 20m from the garage.

Still got my compressor for the ratchet, hammer and saw, but now use the big dewalt impact gun with a 5aH battery for heavy duty stuff. It delivers 850nM so as good as any air tools.

I picked the bare unit up for £150 on eBay, but then all my general power tools are dewalt so I’ve got batteries and chargers already. (Be careful to get the wrench one, they sell 2 power versions, one is a compact one which would serve well as a ratchet but they call t wrench which is a pita)

Edited by eltax91 on Sunday 16th June 09:49