Air Wrench for a Power Draw Bar

7milesup

7milesup

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Hi Guys.
I have a Sharp LMV knee mill with a Kurt PowerLock drawbar (Kurt PowerLock), but of course much older than the one in the link. It has a Chicago Pneumatic CP720 butterfly air wrench which leaks air like a sieve. I took it apart last night, and the o-rings for the butterfly valve are in bad shape. I managed to get them off and turn them around to see if I could reduce the leaking but no joy. I could order new o-rings from McMaster and hope that fixes it, but who knows what else is worn out.
My question is this; how many ft/lbs of torque would be "normal" for a power drawbar? 75ft/lbs or 90? The old butterfly wrench was a Chicago Pneumatic CP720, which I can find no data on. I am considering ordering a new one, such as this Jet with 75lbs of max torque. The Chicago Pneumatic CP7722 has more torque supposedly, but is it necessary? I could also drive up to Menards and buy this Powermate one for $30, but it has not-so-good reviews on other sites.
I realize that I may have to fabricate a new mounting system but then again, all three that I linked look pretty much the same as the one that came off of my mill.
 
I'm pretty sure Kurt would not have put a Harbor Frt pneumatic wrench on their tool. So someone has replaced the original. I'm also pretty sure that 75 ft #s is more than enough pull. Given how simple the impacts are to take apart I'd be inclined to put new O-rings in and go. You can get plumbing O rings @ about any hardware store for cheap. It isn't like that tool will run hours on end. If you have some, put plumber's grease on them while you have it apart. It might resist condensate water better. Cheap, easy solution if the sealing surfaces aren't rough.
 
Larry$ said:
I'm pretty sure Kurt would not have put a Harbor Frt pneumatic wrench on their tool. So someone has replaced the original. I'm also pretty sure that 75 ft #s is more than enough pull. Given how simple the impacts are to take apart I'd be inclined to put new O-rings in and go. You can get plumbing O rings @ about any hardware store for cheap. It isn't like that tool will run hours on end. If you have some, put plumber's grease on them while you have it apart. It might resist condensate water better. Cheap, easy solution if the sealing surfaces aren't rough.
Click to expand...
Chicago pneumatic is not harbor freight. CP is an older more recognized supplier of air tools.


I would just replace the O rings, they are probably all that is needed. All the parts in the wrench are easily replaced.. they are meant to be serviced.
edit: Don't be afraid to take it apart and service it.
 
It's a Chicago Pneumatic, not a Central Pneumatic. The CP-720 was stock on the Kurt Drawbars
 
I've been using a Princess Auto one, equivalent to your Harbour Freight on a home made drawbar for a few years now. Seams to work fine. I only ever let it hit a few times tightening and have never had it come loose.

Greg
 
woodchucker said:
Chicago pneumatic is not harbor freight. CP is an older more recognized supplier of air tools.


I would just replace the O rings, they are probably all that is needed. All the parts in the wrench are easily replaced.. they are meant to be serviced.
edit: Don't be afraid to take it apart and service it.
Click to expand...
Ok. I will give that a shot!
 
Check your cylinder to make sure the chrome plating is still ok before wasting time re-building it.
 
I was able to find some o-rings at the hardware store and will give them a shot. There was enough oil in this wrench that lubrication certainly was not a problem.
 
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