Clamshell Cope and Drag Hinge (No Pins) Al parts to be cast.

Discussion in 'Sand Casting' started by Melterskelter, Feb 13, 2021.

  1. great work!

    More than one way to skin a cat
     
  2. Melterskelter

    Melterskelter Gold Banner Member

    One thing I did to make mating the cope and drag easier was to use a small mirror strategically positioned so I could see the notch in the cope and in the drag and the 1/2" pin as I was guiding the cope onto the drag. The problem is that the cope is modestly heavy---40 pounds or so and is large enough that when held close to your chest it blocks the view to the hinge pin. By putting a mirror in the right place you can see the approach of the cope to the drag and get good initial alignment. Once the cope rests on the pin it is self-guiding. One of the reasons I used this system is that the casting is only 1/8" thick, so side-to-side registration has to be held very accurately. The pin and tab system used seems to help maintain alignment well.

    Mirror assist.JPG

    Hmmm, I am not sure that what I wrote will make any sense. I tried. ;-)

    Denis
     
    Last edited: Feb 19, 2021
    Billy Elmore, Tobho Mott and dennis like this.
  3. Chazza

    Chazza Silver

    Top work Dennis!

    Lots of useful tips for me in this thread,

    Cheers Charlie
     
  4. Billy Elmore

    Billy Elmore Silver

    Cool project! There are a lot of ways to skin a cat. I am lazy and would have just used a side riser or a smaller spherical shaped riser on top with a generous radius around it at contact. You are only feeding the size of the shrink you have in castings so usually not much bigger than the size of the shrinkage is needed. You got it right with no shrink though and that is what matters.
     
  5. Melterskelter

    Melterskelter Gold Banner Member

    Yes, my initial plan was to make a little side riser on each of the four areas that shrank. But then it was just easier to make a large rental riser an tap it 4 times with the “x- shaped riser/pouring basin/gate. Since I’ll be doing this over and over I think this actually takes me less time than fiddling with placing risers, cutting gates and cutting runners.

    The initial run of parts passed inspection by the customer. So, as soon as my electric furnace is set up and I’ve made another clamshell flask set, away we go.

    Could you sketch what you would have done?

    Denis
     
  6. Billy Elmore

    Billy Elmore Silver

    These are not great but just a general concept. If you do a side riser you can gate into it to keep hottest metal in riser. If you use the top riser you can create a hot spot in the top by cutting a v-notch groove across the top of it....make it get real small and tight in the bottom to create the hottest pocket of sand you can to keep it feeding longer. You can use the runner for a riser if it is close enough to the casting and the casting is in drag and runner in cope and ingates are thick enough to feed. The biggest reason for failure on risers is creating hot spot where it connects or having it in the wrong spot or having it lower in the mold than the part you are trying to feed. It usually is not due to being too small.
     

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  7. Billy Elmore

    Billy Elmore Silver

    I did this in too big of a hurry...the notch should be deeper.
     
  8. Melterskelter

    Melterskelter Gold Banner Member

    Thanks, Billy. Now I am trying to imagine how to apply those thoughts to my project.

    Denis
     
  9. Melterskelter

    Melterskelter Gold Banner Member

    Well, 5 months later I have cast 52 of the sewing machine parts. As soon as the buyer sends me a shipping label the box will go into the mail. Feels good to have the order completed with two spares to boot.

    Completed Order.JPG

    I will say that casting the same part over and over seems like a useful exercise. All through the process of packing up 3 molds at a time (2 parts to a mold) I continued to refine my methods. After a while I learned the spots that wanted to cause trouble and devised ways to make the seams cast cleaner and cleaner.

    Along the way I learned to make oil-bound sand (thank you Tom Cobett for the knowledge and Mach for the organophillic bentone) which allowed me to economically make more sand and therefore more molds at a time. The shop-made sand was every bit as good as the commercial product and, in some ways, better.

    It is also interesting to me that for each mold about 2 pounds of aluminum needed to be melted but only 10 ounces actually went into the parts. So I ended up melting and remelting the same aluminum several times since I certainly recycled the pouring basins, sprue and distibution/riser part of the pour. I could not tell that remelting (resistance wire) the aluminum repeatedly in any way degraded its qualities.

    Denis
     
    Last edited: Jul 2, 2021

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