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dissimilar metals

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  • dissimilar metals

    O.K. the heck do you spell dissimilar???????
    Next my problem...In a hydraulic application I have an aluminum block with a metal hydraulic hose fitting screwed into it. It's been in use for quite a while so the hoses are in need of replacement. Unfortunately the metal has reacted to aluminum and now the two are "fused" together. The aluminum block is not replaceable but the metal fittings and obviously the hoses are.
    I can't use heat because there are rubber o-rings in the aluminum and also in a valve that is bolted to the aluminum block.
    Any ideas?????
    After getting these darn things apart what could a guy use to elimnate this problem in the future?

  • #2
    Try a good penetrating oil, like Aerokroil or similar product. after a few days or more of repeated application you can also try gentle heat on the fitting you want to get out. Something to change to fit by expansion/contraction, followed by more penetrant and a good set of wrenches. Might even be possible you may have to use an easy out driven into the fitting and destroy it to remove. When you put it back together, use anti-seize compound, available at auto parts and other outlets.


    • #3
      I had to replace a u-joint on my truck last weekend. Bearing cups would not drive out, so I took a can of aerosol "Freez-it" that I got from the Enco catalog and sprayed the cup until it got frosty. It shrunk so that it pushed out with just a couple of taps. A lot safer than heat, and works just as well. "Freez-it" is the name, and shrinkage is the game...


      • #4
        Just in case I missed the obvious, spray the fitting that you want to shrink, not the outside housing that you thread into.


        • #5
          Ooooo shorty you have a problem. Some more info is needed, has the assembly been in a wet environment? If so, plain water or salty water? The packings should be able to withstand some heat, say 250*F or so. If push comes to shove can you dismantle the aluminum assembly? There are port inserts on the market, if the threads are damaged, that are locked inplace with integral keys or ring locks.

          Neil Peters
          Neil Peters

          When on the hunt, a broken part is better than no part at all.


          • #6
            freez it....I'll try that. Like I said, heat isn't really and option but I can get to the fitting without too much trouble.
            The unit is in an indoor application. No rain water. I live in Alberta so no salt water either.
            I don't really want to use heat as the valve involved is about $1000 to replace and there are about 60 of them in the same type of condition.
            Any-who, thanx for the ideas and any more would be appreciated....I'll keep you posted..


            • #7
              Are the fittings you need to remove the hose end fittings?
              If so, can you cut off the old hoses carefully and replace the hoses in place, without disturbing the fittings?

              A die grinder with a small cutoff wheel may help slit off crimped on ferrules.
              New hoses can be crimped or clamped on the old barbs.

              Of course without seeing it I have no idea what you have to do, but its an idea....

              Hope this helps.


              • #8
                Actually cutting is not an option as these are high pressure hydraulic hoses and need the fittngs pressed on. I got a couple loose today by putting a 3lb. hammer on one side of the aluminum block and striking the other side with another smaller hammer. It dostorted to metal enough that with a pair of vise grips and the small hammer hitting the vise grips I was able to get the smaller fittings loose......still working on the big ones though.
                I soaked them with penetrant and am going to try using a small propane torch tommorrow.
                To add insult to injury I discovered that the threads have been "loc-tite'd" so I'm goint to heat the block slightly I guess....


                • #9
                  eat the fitting away with nitric acid.
                  Non, je ne regrette rien.