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Thread: Little Off Topic, Cutting Styrofoam

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  1. #1
    Join Date
    May 2005
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    Default Little Off Topic, Cutting Styrofoam

    So what I need to do is cut two styrofoam spheres in half, one is smaller than the other.

    The inside of one half of the larger sphere then will have to be hollowed out so that half of the smaller sphere will fit inside of it. I really don't have any way to do this with heat.

    Any ideas how I could go about this? Maybe a fine metal cutting blade, like a hack saw, to cut them in half. But how to hog out the larger sphere?

    My daughter has to make a 3D model of a bacteria cell that is shown as spherical with two layers.

    Thanks in advance.

    Jeff

  2. #2
    Join Date
    Jan 2006
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    If you can't use a "hot wire" cutter, the use a "fillet" knife. Usually any attempts at "sawing" styrofoam makes a static charged mess.
    Today I will gladly share my experience and advice, for there no sweeter words than "I told you so."

  3. #3
    Join Date
    Dec 2008
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    Default

    I have actually used an electric carving knife to cut foam. Not sure how to hollow out the center, tho.

  4. #4
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    Like TECHSHOP said, a hot wire.

    Piece of nichrome wire. Hook it to an adjustable power supply. Use a straight piece of wire to cut them in half then use a heavier piece of wire to make a loop on the end of the stick to make something like a ice cream scoop to hollow them out. You dont want the wire red. Just hot enough to slice through without melting the surrounding foam.

    A car battery charger might work. Hard to say though, there are a lot of variables here.

  5. #5
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    Default

    Crush some glass to a coarse loose powder equal to about 20 grit. Stick a spare small sphere on a broomstick end with low temp hot glue. Paint small sphere with white glue and thoroughly coat with crushed glass. When dry use in lathe or drill press to grind out a matching cavity. Keep a vacuum handy during the operation.

    The best way to crush glass is to use a short length of pipe, maybe 6" long by 2" diameter and weld it to a small piece of plate. Then drop in some chunks of broken glass and use another chunk of bar stock like a pestle.
    Free software for calculating bolt circles and similar: Origin now settable to bottom left! All values positive. Click Here

  6. #6
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    Jan 2003
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    For cutting the spheres in half Harbor Freight sells a hot knife for $14.99. If you sign up for email advertisements than every Thursday you'll get a 20% off coupon for any single item.

    Might be worth a try.



    http://www.harborfreight.com/cpi/cta...emnumber=66182

  7. #7
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    Pleasanton, CA
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    Default

    Low temp, hot melt glue is good for styrofoam. Typically does not deform the material. Good for mounting the stock.

    All normal tooling works fine, but creates a big dusty mess.

    A radius cutter, like a Holdridge would make short work of the job.

    DJ

  8. #8
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    For a one-off project like this a razor blade will do the trick.

  9. #9
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    Feb 2005
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    Default

    I've had good luck grinding the stuff with a sharp coarse aluminum oxide wheel or disk.

  10. #10
    Join Date
    Dec 2008
    Location
    Waukesha WI USA (20 miles W of Milwaukee)
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    623

    Default Stainless steel bacteria

    Quote Originally Posted by chriskat
    My daughter has to make a 3D model of a bacteria cell that is shown as spherical with two layers.
    Sorry for posting twice in the same thread, but my idea of using a stainless steel bowl, gave me the idea of your daughter making a stainless steel bacteria instead of a styrofoam bacteria, since you can probably work stainless easier than styrofoam. Or maybe plastic bowls...

    Now a little (very bad) microbiologist humor, are styrofoam and stainless steel bacteria gram-positive or gram-negative cell walls?

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