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Cutting plastic

  1. Nov 19, 2011 #1
    I have a project where I need to cut some lexan that's about 1/8th inch thick. What's the best way to cut it? Using a saw?

    I thought about using heat somehow to cut it, because I have to cut a circle out of it, but I don't know how to rig up something like that.
    I have a little dremmel saw that's just too weak to cut it. Whenever I put any kind of pressure on the plastic from the saw, the saw stops.

    What do you recommend? Thanks.
     
  2. jcsd
  3. Nov 19, 2011 #2

    turbo

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    Is the hole going to be a "standard" size (and not too big in diameter)? I'm thinking in terms of a hole saw - the kind with a central drill bit. You'll probably have to clamp the Lexan to a piece of scrap wood to give you something solid to push against as you saw.
     
  4. Nov 19, 2011 #3

    dlgoff

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    How big is the circle you want? You could make a template and use a router.
     
  5. Nov 19, 2011 #4
    If the Lexan doesn't come with an adhesive covering, get some painters tape and cover the surface before you cut it. A hole saw will work, router is probably the best idea, but a jigsaw will work just fine if you need to cut a non circular shape. Different speeds will give you different results, so try it out on a scrap piece before you start the real thing. You don't want it to heat up and melt. As mentioned above, support the whole area of the glass on something, particle board, or whatever. If you just prop it up between two saw horses you are asking for it to go wrong.
     
  6. Nov 19, 2011 #5

    Dembadon

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    [PLAIN]http://lh3.googleusercontent.com/public/JVQzHv29BPZZKoomFArRbdx3FwG7OcsbHIUbzgUs4YhRvzICfr_-4cx5y2DCfL9VmQ-E6wYfNsM0nAfj7qw454T2cRvEdvc5cp8bvXcF3-FvhWBtmzlrvyjnTcV8YVdDUHo-Fpwg_RmhyeBeL7W8dPh0Qs9oEoJtknGI1T_Y1EDorVi7EcezrJR4UUGu-bu_K6kKABRvqst4GwZ7oTvyTYQ-S9pOLD_-OKHkabRfRS3lBth7zCpxBTvPQkmZYtsxFoPb_WG3EBhHTSBBf87PSyBh27MP3y-a9GQb__e70mjxMAW_w993aiaG3lduBonVW_2epaA6sFRz9O8Nr18wJew [Broken]

    This is what I used in my dad's glass shop. Use a straightedge and score the lexan sheet with the tool. It should only take about 8-10 passes for 1/8". After that, it should run-out perfectly and you can cut it away from the protective sheet with a utility knife.

    When cutting a big circle, cut a square that matches the diameter of your circle, then you can just cut the corners off and file down the rough edges with a belt sander.

    Do not use a drill for (small) holes unless you have a special bit or you'll risk cracking the plastic or injuring yourself. I've used the incorrect bit before and the lexan sheet "grabbed" the drill bit, causing it to crack as well as whip around and almost take my thumb with it. If you want to try using a regular bit, go extremely slow and use some form of lubrication. Antifreeze mixed with water can also prevent it from getting hot when applied to the area you'll be drilling; it's what we used when drilling mirrors so they didn't heat up and run-out.

    Edit: I might be able to post a picture of what I'm talking about if that would help.

    2nd edit (product info):http://www.google.com/products/cata...fjPITruFJ-KYiQKuwpXBDw&sqi=2&ved=0CHQQ8gIwAA"

    Here's what I mean: (sorry for sloppy picture, I'm a terrible artist)
    [URL]http://i814.photobucket.com/albums/zz70/dem9180/lexan-pf.jpg[/URL]
     
    Last edited by a moderator: May 5, 2017
  7. Nov 19, 2011 #6
    This looks like something that could easily take a nasty chunk out of you if it slips, also it's looks horrible for irregular shapes and not for actually cutting through something.

    Is 'Lexan' the same material they use for machine guards? Soft, scratches easily but is very tough?

    Drilling this stuff is easy. Sharp drill bit (HSS is fine), high rpm, low pressure. Let the tool do the cutting, you shouldn't have to use any force.

    Toothed blades (jig saw / hole saw) will be the best for cutting and working with it. A cutting disc for steel will clog and melt its way through so don't bother with this, however an abrasive fiber disc in the grinder works well for cleaning rough edges. Can be very dusty so I recommend a respirator for prolonged work.
     
    Last edited by a moderator: May 5, 2017
  8. Nov 19, 2011 #7

    turbo

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    Yes, Lexan is a polycarbonate material. It is frequently recommended for the lens-material in eyeglasses for children and very active people because it is very tough and almost impossible to shatter. It scratches very easily though, and there is no coating that can solve that weakness. As an optician, I would recommend polycarbonate lens materials for all childrens' eyeglasses. It's a bit more expensive than traditional plastic lenses, but if the parents balked, I would let them see a handful of regular plastic lens material that shattered with the standard ball-drop test. Got a kid that likes to play sports, roughhouse, and is generally hard on eyeglasses? They NEED polycarbonate lenses for the sake of saving their vision under hard use. I worked for a very large ophthalmic practice (surgeons, not optometrists) and it was heart-breaking to see kids rushed in for emergency surgery because their optometrists had fitted them with cheaper plastic lenses that shattered due to a thrown baseball, a fall, or other incident.
     
  9. Nov 19, 2011 #8

    DaveC426913

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    What does this mean?
    Does it mean:
    - the finished piece has a hole cut out if it
    or does it mean
    - the finished piece is the circle that was cut out?

    The reason I ask is because, if the former, Dembadon's suggestion is moot.

    Even if the latter, I wouldn't recommend this. You'll be sanding forever I only use a blade when cutting a straight edge.

    What I usually use for cutting Lexan sheets is a jigsaw with a fine-toothed blade. Try it on a piece of scrap. Course teeth with shatter the Lexan.
     
  10. Nov 19, 2011 #9

    Dembadon

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    You aren't supposed to use it to cut all the way through the material. You make about 8 passes to score the plastic. It comes apart with little to no effort after that.

    Sanding forever? He has a Dremel! Depending on the size of the circle and grit of the bit he uses, it shouldn't take longer than a few minutes to round off the edges. If it's a larger circle, he could make four more cuts if sanding is going to be an issue. I've literally cut hundreds of circles out of plexiglass during my 7 years at the shop. Trying to cut a nice looking circle without a jig is more difficult than making four straight cuts with a straightedge.

    If it's going into a frame and lumpy edges don't matter, then don't worry about using a jig should you decide to go the saw route.
     
  11. Nov 19, 2011 #10

    DaveC426913

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    The issue still remains whether his finished piece is the circle itself - or the piece with the hole.

    If the latter, your method won't do.
     
  12. Nov 19, 2011 #11

    dlgoff

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    I'm guessing which ever it is, he's used these suggestions and has finished the cutting. :biggrin:
     
  13. Nov 20, 2011 #12
    Thanks for the responses.
    The hole isn't going to be a perfect circle, so I can't the circular drill.
    Dembadon, what I have is a large square piece of plastic and I need to cut the circle out of the middle, so it will kinda look like a closed toilet seat. I'm not using it as a toilet seat, it will just look like one.
    Will that tool be able to cut curves, or is it only good for straight cuts?

    I don't have access to a large machine, but I can buy a new hand-held dremmel tool that doesn't stop when I put pressure on the material, if that's what you guys think will work. The one I have now is for polishing small figurines, or something like that, but it came with little sanding blades that can cut, but this tool is way too weak to cut what I'm trying to cut.

    I hope I answered all the questions. And thanks for the replies.
     
  14. Nov 20, 2011 #13

    Dembadon

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    If you're trying to get some sort of ellipse, then that tool will not be your best option.

    If you live close to a Home Depot, Lowes, or another place that rents equipment, then Dave's suggestion to use a jig saw with a fine-toothed blade would be better than the Dremel:
    [PLAIN]http://lh5.googleusercontent.com/public/-EbU9D0FKTHKeY-AF65_R9Mrathc18WBT0sBS_0XBknAznlzX6bM6lFFH0UHD3u9PT3RhtlZ1hePHXTHpNHQ3bB9jhXe-Mh8BfIGLXUbjFNJZzLpX36WC_Awi6xsDzkATRLQYSgu4_SlouWJi7-E-qFUkn90iAabqQnQzq08VVaRfRBSJW_gCEmH_0fGOKKVR-Qs2HeGCTetYaKO6n0pu8_czd4 [Broken]

    If you do end up renting the jig saw, you might need to start the process by drilling a small hole so that you can get the jig saw's blade in position on your sheet.
     
    Last edited by a moderator: May 5, 2017
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