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Thread: Making core plugs for marking out.

  1. #1
    Supporting Member thehomeengineer's Avatar
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    Making core plugs for marking out.

    Hi All
    Following on from the cradle I made for the cylinder block for my 3” scale Foden steam wagon I need to plug the cylinder bores to aid the making out.
    To plug these un-machined bores aluminium plugs were made.

    An average size of each bore was measured and blanks turned and tapped in to the casting. Each end was slightly different due to the flank angle on the pattern which aids the removal of the bore pattern core.

    The smaller bore diameter (high pressure bore) was simply machined from aluminium bar stock and parted off.

    The plug for the larger bore (low pressure bore) was pressure turned from off cuts of 4mm plate blacks, cut out from another project. The blanks were machined at the average size diameter and a taper machined to help the plug engage in the bore. This same taper was also machined on the smaller plugs.

    The photos show the core plugs being manufactured and installed.

    Making core plugs for marking out.-7718cc93-7cbd-4229-91a1-245bf387b81c.jpeg Pressure turning blanks for low be pressure bore

    Making core plugs for marking out.-d51aea96-b40b-438f-b0b5-df0db41230c3.jpeg Cutting taper for lead into bore.

    Making core plugs for marking out.-5164b2fc-8820-4b65-9f86-ee65cbcfb7cf.jpeg High pressure bore plugs from stock bar

    Making core plugs for marking out.-13ad16a5-36fa-473c-b176-3b900cfac8b4.jpeg Ready to fit

    Making core plugs for marking out.-dd05e0f1-39d3-4e78-90c3-11122c86ee48.jpeg Low pressure bore blank pushed into place

    Making core plugs for marking out.-4ab932a9-ace5-4f86-90ac-c4c1f2f83226.jpeg Hammered in to bore

    Making core plugs for marking out.-984cb97b-a7ca-4707-bae0-75be519a7580.jpeg

    Making core plugs for marking out.-057bde66-1f80-4d94-8d61-62c6a44997e9.jpegAll four fitted and blued, ready to mark out bore centres

    Thank you for viewing
    The home engineer

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    Thanks thehomeengineer! We've added your Model Engine Core Plugs to our Model Making category,
    as well as to your builder page: thehomeengineer's Homemade Tools. Your receipt:




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  3. The Following User Says Thank You to DIYer For This Useful Post:

    Philip Davies (Nov 19, 2022)

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    Is there a danger that you might break the casting?

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    Hi Philip
    The plugs are aluminium and considerably softer than the cast iron. Also the plugs are machined to an average diameter so they fit with only a small amount of interference and the aluminium is soft enough to be pressed into the bore. If the cast bores were considerably out of shape or had a lot of flashing I would have cleaned up with a die grinder but this casting had very clear bores. The saddle however needed a angle grinder to dress the saddle before gluing to the cradle.
    Hope this answers your question
    Andy

  6. The Following User Says Thank You to thehomeengineer For This Useful Post:

    Philip Davies (Nov 20, 2022)

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    The first three faces have been machined with a minimum material clean up, just to get the block faces square to each other. I left the casting on its cradle as the marked out lines help to get everything aligned with a scribing-block. The cradle and cylinder block had to be shimmed and clamped down to the mill table. As the cradle is made from wood light cuts were taken until the face was cleaned up. The second and third faces were machined using an angle plate with the first face clamped against the angle plate. The block again aligned with scribed lines and a scribing block. The third face was placed on parallels and clamped back to the angle plate.

    Making core plugs for marking out.-33936d11-e5bc-4294-bd37-997d13079c17.jpeg First face being machined

    Making core plugs for marking out.-8b1a52c2-19a4-4837-8af2-54b067fb707a.jpegThird face being machined sat on parallels

    Making core plugs for marking out.-a84c9888-160c-48ae-baf1-440fd3ece335.jpegMaking core plugs for marking out.-c18cc58b-f7c6-46bb-8885-8818bba988a7.jpegBoth valve faces square to the regulator face.

    Next stage is to machine the bore faces square to these three faces. Then another check to make sure I am happy that the casting is still going to align all features in the correct place.

    The home engineer



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  8. The Following 2 Users Say Thank You to thehomeengineer For This Useful Post:

    Frank S (Nov 22, 2022), Philip Davies (Nov 23, 2022)

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