Air impact wrench

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Old 11-17-15, 03:58 PM
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Air impact wrench

I am restoring an old car and plan on buying an Air impact wrench and compressor. I am not able to spend hundreds of dollars on a air gun but I need one up to the task of taking off 40 year old rusted bolts. I know I need a gun that has enough torque but I'm not familiar with just how much torque and what specs eg. rpms, working pressure, average air consumption and drive size I need. I have also seen terms like Single hammer rocking dog mechanism and double hammer rocking dog mechanism which I dont understand. Also I noticed on one wrench I was considering it had "Bolt Capacity" of 5/8". I am assuming that means thats the largest size bolt it can remove? If thats the case its useless for my needs. Any education on this would be great.

I will be using a 7 gallon 100 psi compressor to run my gun.
 
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Old 11-17-15, 04:10 PM
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How many gal. and PSI are not what you need to be concerned with, CFM for the tool your planning to use is far more important.
This one should be able to do anything you throw at it.
Ingersoll Rand 232TGSL Super-Duty ThunderGun Street Legal 1-2 in. Air Impact Wrench
 
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Old 11-17-15, 04:17 PM
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You should consider adding a second tank for extra air storage too as the impact guns use short but large bursts of air.
 
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Old 11-17-15, 04:46 PM
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nice gun but a bit out of my price range. Any other you would suggest?
 
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Old 11-17-15, 05:03 PM
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Maybe a gun from Harbor Freight..... 1/2 in. Professional Air Impact Wrench
 
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Old 11-17-15, 05:59 PM
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good suggestion. Is there an advantage of a 3/4" vs a 1/2"?
 
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Old 11-17-15, 06:49 PM
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Your going to be hard pressed to get a good result with a 1/2'' wrench and the 3/4 is way out of your league with the compressor your planning on using. Too much torque with an impact wrench will more than likely break bolts/nuts off it they are that bad, there are times where heat is required. Impact wrenches are not the cure all that you may think they are when it comes to restoring old vehicles but they do have their place.
 

Last edited by Ron53; 11-17-15 at 06:50 PM. Reason: spelling
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Old 11-18-15, 02:58 AM
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I have one of harbor freight's cheaper 1/2" impacts [paid less than $20 over 30 yrs ago] and it has preformed decent but it has a low torque rating which means sometimes I have use a breaker bar [maybe with a cheater pipe] to break stubborn bolts/nuts loose. If I ever buy another one I'll pay more attention to the torque rating. I think mine is rated at 250

In post #1 you said you plan on buying a compressor then said you already had one
While a 7 gallon [1hp?] will be fine for operating an impact in a home shop setting, it isn't large enough for sanding and painting ...... if you plan on doing that later.
 
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Old 11-18-15, 08:04 AM
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I have a higher end Harbor Freight (I know, contradiction in terms...) gun and it's something like 600 ft lbs, so more than enough for everything I need.
 
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Old 11-18-15, 09:51 AM
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I just first want to reiterate what Ron said about an impact not being a cure-all for getting things apart. Depending on what your car is, availability of parts can vary from the local parts store to ebay or whatever to darn near impossible. So you want to proceed carefully, and a lot of times that means soaking with PB Blaster, Break-Away or whatever you choose, some heat, and a fair amount of patience, as well as certain other tricks that you will pick up along the way. You'll have lug nuts, suspension components, possibly including spring shackles and axle bolts, harmonic balancer bolt, and a few other things, but probably not all that you might think. How about an electric impact, which isn't going to do what an air one will, but will take you a long way when combined with a good old breaker bar to get things started. As far as an air impact, toss the notion of a 3/4", because the air compressor for it is going to bust your budget, and, in my opinion, it's not at all necessary for what you're doing. Too heavy and gangly to be any fun on a passenger vehicle. And even a 1/2" impact is going to require a decent size air compressor if you expect it to provide maximum performance. I have four air compressors, but two don't count because they are for nailers, etc. My old 5 horse Quincy will run my Chicago Pneumatic 734 impact all day, no problem. Connect that same impact to my 1 horse on a 15 gallon tank, and the impact works, but it needs the help of a breaker bar on stubborn bolts. Reason being that a 1/2" impact is going to want around 120 psi, which is about the maximum that a single stage air compressor puts out. And that's 120 psi maintained to the impact, so the very second that you pull the trigger, the pressure starts to fall, and the performance starts to fall. I also believe that part of what you pay for in higher end impacts is the tolerances, and that the cfm required for them is going to be less than on average than for lesser priced ones. Bottom line is that, if you're going pneumatic for a wrench, I would look at two stage and a minimum 2 horsepower air compressor. At that point, there are a lot of good prices on two stage 5 hose units, not top of the line, but decent, and all the air you would need, depending on your over all budget.
 
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Old 11-18-15, 03:54 PM
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thanks for all the suggestions. i have been working on cars for years using wrenches etc. but because I have an issue now with my shoulder I cant turn a wrench as strongly as I used to so I was considering the pneumatic wrench to help me along. I will be taking the rear differential/ trailing arms and rear spring out of an old corvette. Having watched some videos by a shop that did the job they seemed to handle it pretty well with a pneumatic but i need to be sure the one I get can handle the project before buying as well as the appropriate compressor.
 
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Old 11-18-15, 04:52 PM
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A few things to remember. Horsepower of the electric motor driving the compressor is vastly overrated. So-called "compressor duty" motors are almost universally 3450 RPM motors and are constructed to only deliver the rated horsepower for a short period of time, the last few psi before the machine shuts down. Because of the speed rating they use high ratio belt drives to lower the speed for the compressor pump to a more reasonable 900 or so RPM. This high ratio loses a lot of power.

Non-lubricated and direct drive compressors are mostly junk. The best home-shop compressor is a twin piston oil lubricated model.

Most pneumatic tools are designed to operate at 90 psi AT THE TOOL INLET so a compressor that cuts out at 125 psi is just fine. However, most compressor kits have woefully inadequate hoses. ALL pneumatic tools have their air consumption rated as an average over a one minute period of time. What this means is that a typical impact wrench is rated as having an average air consumption rate of 4 CFM but they fail to tell you that is rated as a ten second burst of usage every minute. In reality the wrench requires about 24 CFM of air flow for proper operation and both the compressor (with receiver tank) and the hose (with any regulator, quick disconnects and oiler) MUST be able to flow at least 24 CFM at 90 psi AT THE TOOL INLET for proper operation. For this you need at least a 3/8 inch diameter air hose no more than about 25 feet long. For longer hoses you need to increase the inside diameter.

Impact wrenches that are rated in torque are almost always home-shop tools and wrenches rated in bolt size are usually industrial tools. Pneumatic tools DO need internal lubrication and the type of oil used IS important. For most home-shop usage merely adding ten drops of air tool oil into the inlet before starting work for the day is sufficient. If you are using the tool pretty much constantly then add another five drops every couple of hours. If you get anything more than a very fine oily mist out of the exhaust then you are using too much oil. Die grinders and sanders are a noticeable exception and need more frequent oiling or a continuous oiler but still only the finest mist of oil from the exhaust.

There is more but I need to take my shower and get ready for dinner with my sister.
 
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Old 11-18-15, 06:20 PM
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wow I'm looking at air compressors eg 8 gal. 2 HP 125 PSI Oil Lube Air Compressor with an Air delivery: 4.5 CFM @ 90 PSI, 5.5 CFM @ 40 PSI. I havent seen any home size compressors that indicate a flow of 24cfm. Also what does "bolt capacity" mean?
 
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Old 11-18-15, 09:44 PM
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Also what does "bolt capacity" mean?
An excellent question and one I don't think I can give a satisfactory answer. In essence, it means the wrench is capable of tightening or loosening that size bolt under ideal circumstances. A wrench rated at 5/8 inch bolt capacity would be powerful enough that with the proper air pressure at the inlet (90 psi) it could tighten or loosen a 5/8 inch diameter bolt to a "standard" torque rating for that size bolt. I don't know what a "standard" torque rating might be but I suspect something like would be used in a grade five or maybe a grade eight bolt as shown on standard charts like this one.

https://www.boltdepot.com/fastener-i...ed-Torque.aspx


I see that I was a little vague in answering the part about the compressor. Since the wrench is NOT used continuously the compressor does not need to output the full flow required by the wrench, that being taken care of by the air stored in the receiver. Ideally, the receiver pressure is above 110 psi and the air pressure regulator is set to about 100 psi to compensate for the pressure drop through the regulator, quick connect fittings and the hose. How long the receiver will supply the tool before the pressure at the tool drops below 90 psi is a function of the volume of the receiver and the initial pressure. Although this CAN be calculated it has been more than a dozen years since I have done such calculations and I would need to go back to the text books and notes to remember HOW to do it. Short and sweet, the bigger the volume of the receiver and/or the higher the compressor output in delivered CFM at receiver pressure the longer you can use the tool.

This is rarely a problem when using an impact wrench because such use is intermittent. Sanders, polishers, grinders and even scalers, chisels and panel cutters are likely to be used for longer intervals without stopping and this is when compressor capacity is most important.

So, when looking for an air compressor you want the largest CFM output AT receiver pressure as well as the largest receiver that you can afford. Ignore horsepower ratings except for determining the electrical requirements need to power the machine. Use the largest inside diameter and shortest hose as practical. You CAN use a short piece of smaller ID hose (a few feet) directly attached (no quick coupler) to the tool with a quick coupler to connect to the larger hose.
 
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Old 11-21-15, 11:19 AM
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So on a pneumatic 1/2"do i need to purchase sockets made for pneumatics. I have seen these in the stores and figured that regular hand tool sockets were not compatible. Also i have heard that using 8 point sockets result in a better grip with less stripping /rounding of bolt heads rather than the 12 and 6 point sockets.
 
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Old 11-21-15, 11:34 AM
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Impact sockets are heavier/stronger than regular sockets. I'd have to double check but I believe all my impact sockets are 6 point.
 
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Old 11-21-15, 12:16 PM
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Impact sockets are much harder and tougher than standard sockets. While I do have a set of impact sockets I usually use a standard socket and I have never broken one.

Eight-point sockets are only for use on square nuts/bolts. Six-point sockets are stronger and much less likely to round over the points on hexagon nuts or bolts. I don't think I have any twelve-point sockets anymore because of the rounding over problem.
 
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Old 11-21-15, 12:26 PM
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thanks most of mine are 12 points so I'll need to look into some 6 points. Can impact sockets be used on a standard socket wrench? I would imagine they are deeper in length which might make it harder to fit into some spots.
 
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Old 11-21-15, 12:27 PM
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@Furd
[QUOTEI don't think I have any twelve-point sockets anymore because of the rounding over problem. ][/QUOTE]

12 point is very alive and well. Fact is some fasteners are 12 point headed.
I have found them in automatic transmissions, hydrostatic transaxles on lawn tractors, etc.
A well equipped tool set will include 6, 8, and 12 point along with Torx male and female wrenches.

RR
 
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Old 11-21-15, 01:15 PM
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I didn't mean to imply that twelve-point sockets were obsolete, only that I don't have any. I know about twelve-point bolts as well but I don't work on anything that uses them. Truth is, since retirement I try to do as little work as possible.


Can impact sockets be used on a standard socket wrench? I would imagine they are deeper in length which might make it harder to fit into some spots.
Absolutely! The impact sockets are thicker walled so are physically larger than hand sockets so yes, in some instances they will not fit into small spaces.
 
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Old 11-22-15, 03:54 AM
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While I occasionally use a regular socket on my impact, I mostly use impact sockets. I wallowed out a 5/16" [?] socket years ago using it on a cordless drill to remove a lot of screws. I don't use my 12 point sockets often but as RR stated they do have their uses. My previous jeep had a craftsman 12 pt permanently installed next to one of the front axles [wouldn't come off once the bolt was installed] Impact sockets are always 6 point. They aren't necessarily longer but are always thicker.
 
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