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Thread: Help needed to cast human skeleton out of aluminum

  1. #141
    Quote Originally Posted by DavidF View Post
    Looking good!! dont stop now
    Happy Easter everyone! I am trying to crank out four sets of ribs this weekend. Finished the 6th ribs today!

    6th Ribs Mold
    IMG_3673.jpg

    6th Ribs
    IMG_3675.jpg

    6th Ribs Right Side Finish
    IMG_3676.jpg

    6th Ribs Left Side Finish
    IMG_3677.jpg

    I'll have to do some grinding on the 6th left and might have to redo it but I'll handle that at a later time. I'll try to crank out the 7th ribs tomorrow after I drive back from Lancaster; gotta try out the new Petrobond! Thank you all for your support.

  2. #142
    Senior Member Robert's Avatar
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    Looks like a healed fracture to me...
    Robert
    "Whether you think that you can, or that you can't, you are usually right."
    - Henry Ford (1863-1947)

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  3. #143
    Hey everyone! I'm cranking out pieces and should be done with my sixth set of ribs tonight if the weather permits. I'm starting to cut them out of their sprues and am trying to find ways to sand and/or polish my pieces.

    I was told that a Dremel should do the trick but I wanted to check here first. Would a dremel work to grind out imperfections and polish the pieces with the right attachments? If so, what attachments?

  4. #144

  5. #145
    Moderator DavidF's Avatar
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    You will be sanding for 100 years with a dremel.
    A calm sea does not make a skilled sailor....

  6. #146
    Senior Member Zapins's Avatar
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    First - very good job making those ribs so far. Your work is looking very good. I'm really looking forward to seeing the rest of the castings.

    As for polishing the bones... I think you'll find that polishing them is going to take the most time and be the most tedious and not - fun - part of this project. There's a reason I have had 30+ statues in the unfinished unpolished state sitting in my to do list bucket for the last 3 years.

    Sand blasting with a rougher aluminum oxide grit around 120 grit then follow up with glass bead blasting will give you a nice matte finish, not super shiny but not rough either. It would be the quickest way to finish your bones, but if you are dead set on polishing then:

    Tungsten Carbide burrs will fit into your dremel and will very very quickly cut away excess metal. They leave a bumpy surface but are fantastic to cut and shape larger defects. They are invaluable for finishing work. http://www.ebay.com/itm/10x-Tungsten...YAAOSwmgJY1K2H

    You should get a flex shaft for your dremel it makes everything much easier to handle http://www.ebay.com/itm/Dremel-225-0...IAAOSweW5U7R8q

    Then for sanding you can use sanding drums for the dremel or flap wheels. I'd start with 80 grit drums because they are much cheaper than flap wheels and last roughly the same amount of time http://www.ebay.com/itm/80-GRIT-smal...QAAOSwSlBYv3LY 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.

    You can also use Diamond 3x compound which leaves a decent finish, but if you use this compound you'll need to buy another cotton wheel and another polish called red rouge compound to bring it to a high shine finish.

    Mother's compound also works well on Al. It also has a bit of a cutting action and will very quickly polish up your parts. Probably even by using a soft cotton cloth by hand.

    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.

  7. #147
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    Quote Originally Posted by DavidF View Post
    You will be sanding for 100 years with a dremel.
    +1
    You have to decide what level of finish is desired and appropriate on the whole piece. The level of finishing BobS demonstrates in his excellent thread linked above by FrostOak seems unlikely because you don't have the equipment or time. You'd have your PhD by then. I'm not suggesting that you settle for an unacceptable finish, but you'll need to establish your standards pretty early on so you don't have drastically different finishes on your overall work.
    Effective work holding will be crucial. A vise with wooden pads works for me, or sometimes just a couple of wadded rags in the steel vise to protect the aluminum. A coarse hacksaw and a file like this will go a long way.
    http://www.ebay.com/itm/Vintage-NIB-...8AAOSwRUhY99FY. Regular mill files are helpful as well.

    Your shapes will definitely lend to small rotary tools like Zapins showed above, but I've found them to be a real pain if I try to hog with them. They load up aluminum pretty bad with deep cuts. Files load up pretty quickly too, sometimes at just the wrong moment. These too items will be indispensable when using burrs and files.
    http://www.ebay.com/itm/Osborn-Inter...cAAOSw32lYvclj

    http://www.ebay.com/itm/Tungsten-Ste...gAAOSw5UZY994h
    Nothing works quite like a file card for cleaning files, but the scriber will be needed for picking the stubborn bits of aluminum out of the files and burrs.
    That will get you going on the basic cleanup and finishing. The rest of it will depend on what you decide is necessary.

    Pete

  8. #148
    Quote Originally Posted by Robert View Post
    Looks like a healed fracture to me...
    Robert
    Actually, they kind of do. I'll just tell people their healed fractures instead of imperfections

    Quote Originally Posted by FrostOak
    Thank you!

    Quote Originally Posted by DavidF
    You will be sanding for 100 years with a dremel.
    Yeah, I didn't realize what I was asking for. It would literally be forever! However, the Tungsten Carbide tips look really promising.

    Quote Originally Posted by Zapins
    Sand blasting with a rougher aluminum oxide grit around 120 grit then follow up with glass bead blasting will give you a nice matte finish, not super shiny but not rough either. It would be the quickest way to finish your bones, but if you are dead set on polishing then:

    Tungsten Carbide burrs will fit into your dremel and will very very quickly cut away excess metal. They leave a bumpy surface but are fantastic to cut and shape larger defects. They are invaluable for finishing work. http://www.ebay.com/itm/10x-Tungsten...YAAOSwmgJY1K2H
    My main concern right now is removing the excess metal since I can deal with polishing whenever I want; even after the piece is "due" I can come back and edit it including polishing so I'll focus on getting the correct shapes for now. I would love suggestions for polishing but I can put that off for a little. My school actually does have an industrial sand blaster so I'll go down and ask the guys about that and try it out on a test piece. My teachers also already has a Dremel so I'll check the model and then order the correct Carbide tips. Thank you for this excellent post and links!

    Quote Originally Posted by Petee716
    +1
    You have to decide what level of finish is desired and appropriate on the whole piece. The level of finishing BobS demonstrates in his excellent thread linked above by FrostOak seems unlikely because you don't have the equipment or time. You'd have your PhD by then. I'm not suggesting that you settle for an unacceptable finish, but you'll need to establish your standards pretty early on so you don't have drastically different finishes on your overall work.
    Effective work holding will be crucial. A vise with wooden pads works for me, or sometimes just a couple of wadded rags in the steel vise to protect the aluminum. A coarse hacksaw and a file like this will go a long way.
    http://www.ebay.com/itm/Vintage-NIB-...8AAOSwRUhY99FY. Regular mill files are helpful as well.

    Your shapes will definitely lend to small rotary tools like Zapins showed above, but I've found them to be a real pain if I try to hog with them. They load up aluminum pretty bad with deep cuts. Files load up pretty quickly too, sometimes at just the wrong moment. These too items will be indispensable when using burrs and files.
    http://www.ebay.com/itm/Osborn-Inter...cAAOSw32lYvclj

    http://www.ebay.com/itm/Tungsten-Ste...gAAOSw5UZY994h
    Nothing works quite like a file card for cleaning files, but the scriber will be needed for picking the stubborn bits of aluminum out of the files and burrs.
    That will get you going on the basic cleanup and finishing. The rest of it will depend on what you decide is necessary.

    Pete
    So it looks like my best bet is to order a set of Tungsten Carbide tips and one of the brushes to remove the excess metal.

    I know this will probably sound like a stupid question so I apologize in advance but, what is the purpose of the first item if the Dremel is already removing the excess metal? Thank you for the amazing advice and links!

    -------------------------------------

    In summary, from what I gathered, I should buy a set of Tungsten Carbide tips to remove excess metal and a brush to remove the shaving from the tips. How does that sound?

  9. #149
    Quote Originally Posted by Menth View Post

    I know this will probably sound like a stupid question so I apologize in advance but, what is the purpose of the first item if the Dremel is already removing the excess metal?
    Sometimes for some items a good quality hand file works heads and toes faster and does a better job than a Dremel/Rotary tool. Other times just grabbing the file is quicker than messing with setting up the dremel with the right bur for the job. Or if your trying to sneak up on the perfect blend the Dremel can be too aggressive. It's about using the "right" tool for the job.
    But if all you have is a hammer... you get used to eating scrambled eggs If the only tool you have is a dremel you can make it work and it will look nice it just may take a little more time and/or patients.

    Love the ribs so far... Keep up the good work!
    CBB

  10. #150
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    Not to be picky, but the brush is called a file card, not to be confused with a wire brush. It's sole purpose in life is cleaning files, and it does it extremely effectively. You don't want to use a regular wire brush on a file, its bad for the file. But frequently with aluminum you will get bits lodged in the file that just won't come out. That's where the point of the scriber comes in handy. Too, when your dremel burr gets loaded with aluminum, the metal will almost weld itself into the burr. The file card will be useless for removing it. A scriber is the only thing that will get it out. Plus they're cheap as well as super handy. Make sure to wear safety glasses!

    Pete

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