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Thread: Help needed to cast human skeleton out of aluminum

  1. #161
    Senior Member Zapins's Avatar
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    Quote Originally Posted by Menth View Post
    The multi-pack was really cheap so I'll order the pack you suggested as well. Is the buffing pad an attachment for a Dremel or for a completely different machine? I'm guessing it's the later but I wanted to make sure. Thank you for the advice!
    There are felt buffing wheels for the dremel, they are small about 1/2" wide and will polish very small things, or tight crevices but they wear out quickly and I don't think they are the best choice for polishing the bones.

    The better choice is using a 6" stitched cotton wheel like I linked below with a bench grinder. A bench grinder has 2 wheel attachments on either side. You can disconnect the grinding wheels and put in a polishing wheel instead. There are many types of grinder, basically any kind should work as long as it takes a 6" wheel. There are even versions without the housing material around the wheels which make polishing much easier. But even with the protective housing I think it will still work for you (it is what I use).

    Come to think of it, the bench grinder's grinding wheels can also be used to grind away the casting defects instead of the tungsten carbide burs for the dremel. And you can buy a wire wheel for the grinder which can help you clean up the bones or other projects in the future.

    This is a bench grinder. They are cheap and can easily be picked up second hand for even cheaper.


    Quote Originally Posted by Zapins View Post
    ... and then you can use a bench grinder (hopefully you already have one) with a 6" stitched cotton wheel http://www.ebay.com/itm/NEW-DeWalt-D...wAAOSwjDZYg46Q and use "Ryobi compound D" http://www.ebay.com/itm/Ryobi-Buffin...YAAOSwUuhXcF-k Compound D has a bit of a cutting action, meaning if you keep polishing the same place it will erode the metal away in that spot as if you were sanding it but instead of leaving a rough finish it will leave the metal highly polished like glass. I use it for finishing a lot of my bronze sculptures but the tube says it works for Aluminum as well.
    ......

    There are also felt wheels for the dremel that you can use, but they won't last very long and are basically only for small parts or tight nooks and crannies.

  2. #162
    Quote Originally Posted by Zapins View Post
    There are felt buffing wheels for the dremel, they are small about 1/2" wide and will polish very small things, or tight crevices but they wear out quickly and I don't think they are the best choice for polishing the bones.

    The better choice is using a 6" stitched cotton wheel like I linked below with a bench grinder. A bench grinder has 2 wheel attachments on either side. You can disconnect the grinding wheels and put in a polishing wheel instead. There are many types of grinder, basically any kind should work as long as it takes a 6" wheel. There are even versions without the housing material around the wheels which make polishing much easier. But even with the protective housing I think it will still work for you (it is what I use).

    Come to think of it, the bench grinder's grinding wheels can also be used to grind away the casting defects instead of the tungsten carbide burs for the dremel. And you can buy a wire wheel for the grinder which can help you clean up the bones or other projects in the future.

    This is a bench grinder. They are cheap and can easily be picked up second hand for even cheaper.
    Ah! My school has a bench grinder in the transportation department! I'm still happy I got the Dremel bits and polishing pieces for the tiny details but I can ask them if I can use the bench grinder for the large pieces with defects. I'll post my results after practicing with the Dremel on the ribs. Thank you!

  3. #163
    If you are grinding Al on the bench grinder there are all kinds of people who are going to light their hair on fire about the risk... if you do not know about the risk then spend a few moments on google learning. The bottom line is to use a light touch- do not load up the stone and plug the pores- they can be preloaded with a bar of soap or paraffin wax or even chalk like you would a hand file.

  4. #164
    Senior Member Zapins's Avatar
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    Hmm learn something new every day. Never heard of not grinding aluminum on a stone wheel. I just read a few internet posts about it as you suggested. Seems kind of dangerous. Probably shouldn't use the stone wheel for that. Having that grinding wheel break apart while running would not be fun.

    You can still use the wire brush and the polishing wheels on the bench grinder though!

  5. #165
    Senior Member Tobho Mott's Avatar
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    It is probably understood, but just in case this isn't clear to everyone: Dremel grinding stone bits can explode when used on aluminum too; it's not a bench grinder specific issue.

    The assembled skelly is gonna look great! Impressive progress.

    Jeff
    Tobho had learned to work Valyrian steel at the forges of Qohor as a boy. Only a man who knew the spells could take old weapons and forge them anew.

    How I built my oil furnace | My Photo Album | My Videos

  6. #166
    Quote Originally Posted by Quadra View Post
    If you are grinding Al on the bench grinder there are all kinds of people who are going to light their hair on fire about the risk... if you do not know about the risk then spend a few moments on google learning. The bottom line is to use a light touch- do not load up the stone and plug the pores- they can be preloaded with a bar of soap or paraffin wax or even chalk like you would a hand file.
    Thank you for the safety head ups. That could have been really scary trying that without knowing so thank you very much for helping me stay safe.

  7. #167
    Also, unrelated to the skeleton project but I thought you all would like this.

    Since I am in highschool, I was obligated to make a "promposal" for prom which is just a glorified invitation. So I decided to get creative.

    My girlfriend has been super supportive about this casting project but is slightly annoyed about it since it takes so much of my time. So I decided to make her something to show that I'm not completely wasting and would work as a good promposal.

    I used a spoon and a clay carving tool to write out "Prom" backwards in Petrobond and then casted it. I then presented it to her under the impression I was opening a vertebrae and wanted to get a video of it for YouTube . So she started filming completely unaware what was about to happen and here's the entire video; https://www.youtube.com/watch?v=m9o2Ral0JiQ

    Hope you all enjoy. Nine pairs of ribs complete and ready to finish more!

  8. #168
    Senior Member cactusdreams's Avatar
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    Definitely heed the Al grinding warnings! The best tip I ever got on grinding aluminum was from BobS' post about polishing aluminum. FORMAX F-90! I usually grind Al with a grinding wheel on an angle grinder and F-90 prevents all the loading and makes the grinding go quick and clean. Might work with a mounted grinding wheel. Don't know. You need to heat the piece up till the F-90 flows like water then you're good to go. I bet it would work on dremel grinding bits too. My other comment was when I use convex shaped grinders or sanders on a convex surface, I get flat spots or facets. A 1" or 2" sanding belt works good for those shapes. And of course there's always hand sanding.
    People who say it cannot be done should not interrupt those who are doing it.

  9. #169
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    Want to grind aluminum with an angle grinder?
    Rex Cut makes a disk, expensive but works like a charm.
    http://rexcut.com/product/type-27-max-flex/
    I have a 36 and 54 grit and need to order a couple more.
    Bones

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