Lapping machine for piston rings

Discussion in 'Tools' started by Foketry, Apr 19, 2019.

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  1. Apr 24, 2019 #21

    Foketry

    Foketry

    Foketry

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    In the engine i built previously ( Holt 75) i followed the Trimble method
    I made all the tools, but I put the rings in the oven at 800 degrees C (1470 F) but the rings become very soft , sloppy and have lost the spring effect.
    Then I remembered that, as studied at school decades ago, cast iron heated to over 720 degrees changes characteristics.
    I redid the rings again, but only heated to 450 degrees ,the rings were ok , however, I had about 30% of rings with compression problems .

    IMG_9120.JPG

    I am now building the Howell V4 engine
    To replace a ring on this engine it is necessary to dismantle it completely, including the multi-piece crankshaft
    I therefore want to make good rings at the first shot , i am looking for all the solutions to do a good job, included lapping machine .
     
  2. Apr 24, 2019 #22

    Foketry

    Foketry

    Foketry

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    The finished Lapping Machine

    IMG_9097.JPG
    IMG_9099.JPG
    New motor IMG_9098.JPG
     
  3. Apr 24, 2019 #23

    Foketry

    Foketry

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    IMG_9107.JPG IMG_E9116.JPG

    the lapped ring, now i have to turn the outer diameter and the inner diameter

    Thu Apr 11 23-39-15.jpg

    the ring before lapping and after lapping
     
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  4. Apr 25, 2019 #24

    petertha

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    Very cool. How did you take that magnified picture?
     
  5. Apr 25, 2019 #25

    kuhncw

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    That is a very interesting machine and it gives a nice finish. Well done.

    Chuck
     
  6. Apr 25, 2019 #26

    Foketry

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  7. Apr 25, 2019 #27

    stevehuckss396

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    Too hot and too cold. You also didn't say how long you left them in the oven. 1100F for 3 hours is what you want. I have made 4 or 5 batches this way and have made good rings every time.
     
  8. Apr 26, 2019 #28

    nj111

    nj111

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    Thank you for sharing, it's a great machine! Nick
     
  9. Apr 26, 2019 #29

    Echesak

    Echesak

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    That's a great machine for the task. I've needed to lap smaller rings for a work project. I built a small fixture for the task. But I know from first-hand experience that applying even pressure to all sides while doing this by hand, is tricky. It's very easy to end up with rings that are thinner on one side. Thanks for sharing this idea!
     
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  10. May 1, 2019 #30

    CrashedAgain

    CrashedAgain

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    I wrote an article on making piston rings in Home Shop Machinist magazine Vol. 37 No. 1 Jan-Feb 2018 (available as a reprint from http://www.homeshopmachinist.net/). Basically I manually lap the sides similar to what Foktry was doing before making the lapping machine but I also lap the outside diameter after heat treating. Trimble's method (which actually dates back to Prof. D.H.Chaddock in Model Engineer magazine 1967) was to machine a couple of thou off the diameter to true it up after heat treating but I always found that difficult. Lapping is much easier.
    If the rings lose their spring after heat treating it is a problem with the material. Some cast iron is too ductile and just won't work.
    (Which brings up another point......I cannot see any reason why steel rings in a cast iron cylinder would not work???)
     
  11. May 5, 2019 #31

    Wizard69

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    You got some nice results but I have to ask, is that machine built out of glass?
     

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