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  • Material Choice

    Looking for opinions on options for material choices. I have relined the bore of a oil pump, which is cast iron and the plunger is hardened steel that rotates(1500-2000rpm) and travels up and down a 1/4". The clearance between plunger and bore is 0.0002-0.0005 optimally. I have used a cast iron valve guide that I machined and pressed in and honed to size, thinking it would have similar properties to original pump bore. I am second guessing my material choice and wondering if something else would offer better resistance to wear and corrosion as the original bore was deeply pitted. Wall thickness of sleeve is 0.045

    Thanks

  • #2
    The valve guide does sound like a good candidate as a replacement I agree.
    I have to wonder why the original cast iron bore was deeply pitted, especially in oil pump service. Was the oil contaminated with moisture? This and or combustion byproducts in an engine's oil system and allowed to remain there for extended periods for example will lead to corrosion throughout the engines' internals.
    I've seen a lot of roller bearing damage, among others, due to this fact alone.
    Home, down in the valley behind the Red Angus
    Bad Decisions Make Good Stories​

    Location: British Columbia

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    • #3
      Stellite.
      Ask a question and receive an answer, the question does not include any possible cost considerations therefore any material is fair game.

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      • #4
        Originally posted by Bented View Post
        Stellite.
        Ask a question and receive an answer, the question does not include any possible cost considerations therefore any material is fair game.
        In that case, I suggest PEEK

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        • #5
          The cast iron was chosen for wear resistance. Pitting suggests chemical attack rather than wear. Acidic combustion byproducts and/or moisture contamination come to mind, assuming such there are.
          Last edited by MrWhoopee; 04-24-2022, 02:20 PM.
          It's all mind over matter.
          If you don't mind, it don't matter.

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          • #6
            Thank you for the responses. The oil pump is 85 years old so has had a long life with different oils and lengths of time sitting which I'm assuming lead to the the pitting. I should have qualified the material needs to be machinable with home shop machinery and some what cost effective. Stellite looks good but my cursory investigation online indicates its pretty hard and needs to be ground. Peek looks ideal but a quick search indicates in bearing grade is pretty expensive(minimum piece I could find online .750x3.28 ft. was $364.00) The sleeve is .750x 1.300 inches in length, so I would need to find someone who sells in locally by the size required.

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            • #7
              I have turned 20% glass filled PEEK in the past, a nasty difficult material.

              As you have now defined some parameters, cast iron is a direct replacement and will be fine.

              If it lasts another 85 years you will not be alive to regret the choice.

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              • #8
                Thanks for the opinions. Cast iron seems to be the best choice. I have another pump to fix and have no material on hand to do. I will be trying to find a source for cast iron bar in a small quantity. Just wondering if Phosphor Bronze bearing material would be suitable as it is readily available near me.

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                • #9
                  Aluminum-Bronze.

                  -D
                  DZER

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                  • #10
                    Grey iron seems to be a good general choice. Bronze may or may not be good for this application - it needs to be investigated. Stick with the original material unless you are willing to take a risk. Here is a link to a 1.5" diameter rod for a reasonable cost.
                    https://www.zoro.com/zoro-select-rod...d8/i/G0473776/
                    1" continuous cast rod would be better, but I could not find it at the moment.

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                    • #11
                      Turns out they also have 1-1/4" diameter rod.
                      https://www.zoro.com/zoro-select-rod...l9/i/G1944171/

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                      • #12
                        Originally posted by mikey553 View Post
                        Grey iron seems to be a good general choice. Bronze may or may not be good for this application - it needs to be investigated. Stick with the original material unless you are willing to take a risk. Here is a link to a 1.5" diameter rod for a reasonable cost.
                        https://www.zoro.com/zoro-select-rod...d8/i/G0473776/
                        1" continuous cast rod would be better, but I could not find it at the moment.
                        He said he is second guessing his choice of iron for reasons of corrosion.
                        Aluminum-Bronze would potentially see less corrosion and has about
                        the same wear resistance as cast iron. I would say staying with iron is
                        more of a risk.

                        --D
                        DZER

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                        • #13
                          We don't know the cause of the corrosion. It may not happen again if used for a different service.

                          I took apart my old sump pump to find the root cause of failure. It was a burned starting capacitor, but the sleeve bearings (gray iron) were in good shape. The whole electric motor in this pump is submerged in oil by design.

                          Yes, aluminum bronze can be used for bushings and bearings application, alloy C95400 in particular is readily available. It has 2 times the tensile strength of Class 40 gray iron. Will it work better or worse than original gray iron in the particular oil pump? Who knows...

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                          • #14
                            Sulphur in some oils can cause erosion of some brass alloys. Bronze has brass in it.
                            Kansas City area

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                            • #15
                              Originally posted by Toolguy View Post
                              Sulphur in some oils can cause erosion of some brass alloys. Bronze has brass in it.
                              You may want to substitute brass with copper.

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