I tore my ancient CP-734 Chicago Pneumatic 1/2" drive impact wrench apart to install a "tune up" kit and while I had it apart I carefully studied it to see how it worked. It took me quite a while to understand how it managed to "impact" something but I finally discovered it's secret. It has a spring loaded cam that raises up a pair of hardened steel pins that the spinning flywheel "hammers" against the drive end. An impact wrench has two assemblies; an air motor that supplies the torque and a hammer assembly that uh hammers. No "hammering" takes place until a resistance is encountered and then the hammer hammers. And when the hammer hammers the nut or bolt gets tighter until the hammer can't hammer it any tighter.
The average 1/2" drive impact wrench delivers around 400 to 500 ft/lbs of torque but the newer impact wrenches like the Snap On and Harbor Freight's "Earthquake" will deliver over 1000 ft/lbs of torque. I discovered my CP-734 was obsoleted many years ago by a newer CP-734H that delivers a lot more torque but as I only use mine to loosen or tighten lug nuts it's more than enough for my needs.
By increasing the air pressure the impact wrench will perform better so I run 150 psi. I recently installed a larger Harbor Freight v-twin pump that delivers 1-1/2 times the volume of my old pump and at 30 psi higher pressure
On a whim I just bought a new CP-734H Chicago Pneumatic impact wrench because I found a new one for only $106 with free shipping. As the price was so low and I have a right angle drive that is made specifically for the CP impact wrenches I decided to stay with this brand. I'll go ahead and finish rebuilding my old CP-734 and keep it around in case I ever have a need for it. When I was tearing my 454" big block down a month ago I found it was too weak to bust a few of the main bearing bolts loose. The rebuild kit will certainly restore it to it's original power but after using it for 45+ years I felt I deserved a new one. I'll probably croak within the next 5 years so what the heck?
What brand of impact wrenches are you guys using? The more powerful Ingersol Rand? Sears? Harbor Freight?
IR , Blue Point , Astro (3/8) and CP for air and Craftsman lithium C3 (1/2 and 3/8) for battery
I bought my CP used in 1980 and it still works fine
My air ones all ran on 190 psi on nitrogen at the track , now at about 135 on my compressors
I'm looking for an impact air ratchet. My old one died. I'm using a 10-year-old $16.00 regular HF one in the mean time.
I miss my old impact one. Regular air ratchets just aren't the same.....
Funny how you mentioned an "air ratchet" as I bought a Central Pneumatic from Walmart for $30 this last summer and I have never used it.
I very rarely lubed my CP-734 during the past 45 years and when I took it apart I found the cast iron outer ring of the air motor had deep scoring in it. But the scoring came right out when I honed it so what I thought was "scoring" was actually a buildup of vane material. So if any of your impact wrenches or other air tools don't have the power they used to have suspect their air motors need some attention.
I have an old CP-734 Chicago Pneumatic right angle drive attachment that I found in a box of junk many years ago and I have used it a few times. It has a 1 to 3/4 ratio which I think is rather odd. I tried to find them in E-Bay but none of them have turned up so far. Are they exceptionally rare and mine is worth a million bucks? It has no markings on it except for the familiar "CP" logo on one side. I tried to upload a picture of it but I'm getting an ERROR message telling me the file is too big (???). Why can't we upload pictures any more?
Once the vane material gets stuck to the housing I don't think there's any way to remove it other than honing it off. Prior to my taking this CP-734 apart I had run a LOT of oil thru it but yet the vane material remained stuck. Maybe something like gasoline or acetone could be run thru it once in a while (???). But one thing is for sure and that is I'll be sure to lube my air tools every time I use them from now on now that I have seen what a lack of lubrication will do to the motor.
I just bought an inline air tool lubricator thru E-Bay for $15 and I'll install it on my center air outlet and only use THAT outlet for air tools. After seeing how much wear my impact wrench's vanes have I realized I need to be more attentive to lubricating my air tools.
I bought a 3/8" drive Campbell Hausfeld impact wrench from Walmart this last winter and I just discovered something rather odd. It looks identical to a 1/2" drive CP-734 Chicago Pneumatic but about 1/3rd the size. It has a set screw in the side right where the oil fill is for the hammer unit on a CP-734 but it's NOT for oil on the Campbell Hausfeld. I filled it with 60 weight engine oil and it promptly blew it out of the exhaust port (???). Come to find out the air motor and the hammer unit of a Campbell Hausfeld isn't separated like a Chicago Pneumatic and oil in the intake air feeds both the air motor AND the hammer unit. Hmm. So air tool oil can be put into the inside of the Campbell Hausfeld rather than in the air supply. Now that I know what that set screw is for I'll just add oil to the air intake only. Learn something new every day!
I have been using my trusty CP-734 Chicago Pneumatic for the last 45 years and until now I only knew of a few other models. Like the more powerful Ingersol Rand and Milwaukee. But after searching E-Bay I now realize there at least 50 different models to choose from and most boast of 450-600 ft/lbs of torque. So which one is the best? It all depends on what you intend to do with it and of course parts availability is a big factor for those of use who use them often. For my usage the Chicago Pneumatics are more than adequate. but if I were going back to heavy equipment engine building I'd go with a Snap On or Harbor Freight Earthquake that develop over 1000 ft/lbs of torque.
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