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  • press fit clearance??

    Hi
    Very low hour machinist (I have more fingers than hours on lathe) and could use an assist.
    I'm fabricating an aluminum ring to slip over a cast lip 1.100" OD(part that oil seal fits into) on a small Echo engine (similar metal).

    This ring will have very little load, mainly vibration of engine. It just needs to stay in place as it will hold a electrial sensor pick-up.

    I would like to just tap it into place with a mallet.

    How much undersized should the ring be machined?

    Googled but only found stuff dealing with parts with much higher load requirements.

  • #2
    A shrink or interference fit may not work well with a thin section aluminum ring. When the engine heats up it may deform the ring permanently causing it to be loose when it cools down. It depends on the alloy and the thickness of the ring.
    Free software for calculating bolt circles and similar: Click Here

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    • #3
      Press fits can be found in Machinery's Handbook. But for your application, 0.001" under will work.

      The beginning machinist will do well to avail himself of couple of Loc-Tite products. They will help in "adjusting" fits in applications such as this when the lathe misses that last cut.
      Jim H.

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      • #4
        The ring is about .125" thick at present, heavy for a model enginge. Engine alloy unknown, ring stock 60601 T-6

        The ID is getting close, not sure if I have have the skill and equipment to make it work on this first piece. (HF 10x7 on loan)
        Thinking if I miss some set screws and red or green locktite.

        Thanks

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        • #5
          I agree with using Loctite.

          I should point out that different alloys of aluminum have different coefficients of linear expansion. I just looked it up and cast aluminum alloys have significantly lower CLE than most other aluminum alloys meaning that the ring could become loose on heating as it expands more than the casting.
          Free software for calculating bolt circles and similar: Click Here

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          • #6
            miknlapaz
            I use loctite products often in my model engines and other things. I think #290 would work here if I understand your description, I have used it for small part assembly on my holt engine tach. sensor mounting parts. It would also allow you to thin the part down to a lesser crossection and maybe look more appealing.If you can get #609 or the hi-temp #680 they have impressive holding power but you will need to heat the joint to break it. Spray primer sold for prep use before assembly is supposed to make a stronger joint,but also speeds up set time so be careful that you get the part in position before it locks up.
            Hope that helps
            Johnny O
            johnny o

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            • #7
              Aluminum is very abrasive, ss or mild steel is better.

              I have seen 20+ year old seal eat into 4140 .100" and the the seal is still good.

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              • #8
                If high heat isn't a problem, use Loctite 609 with a slip fit (if it's too tight, you'll squeeze out all the Loctite).
                ----------
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