Working With Acrylic

Discussion in 'DIY' started by Mr. Ugly, Aug 16, 2009.

  1. Mr. Ugly

    Mr. Ugly Past President

    Posted this in Andy's thread( http://www.bareefers.org/home/node/8090 ), but figured to start a new one since the topic comes up periodically.

    Go ahead and post questions and or tips about working with acrylic here.

     
  2. phishphood

    phishphood Guest

    Did you mean perpendicular to the drill bit axis?
     
  3. Mr. Ugly

    Mr. Ugly Past President

    Parallel so that the cutting edge is close to perpendicular to the surface of the acrylic when drilling.

    Check the right side of the pic.
     
  4. sfsuphysics

    sfsuphysics Supporting Member

    Or just be VERY careful with drill thin acrylic and go slow and steady... unfortunately many drills only have one speed so might be a bit difficult. I've noticed that the easier it is to "cut" acrylic simply by using that sharp tool and snapping it in half, then the easier it is to crack it when drilling.
     
  5. phishphood

    phishphood Guest

    Sorry Norm, I'm not following. The terminology and pictures aren't clicking in my head, but it's ok. I'll do what I've been doing, and apparently Mike has too. Nice and slow and steady has worked for me with next to no cracks :) But then again I have nothing but time right now too.
     
  6. Mr. Ugly

    Mr. Ugly Past President

    Actually for acrylic, especially with small diameter bits, you want a really high cutting speed, but a slow feed rate.

    Slower feed, especially if using a standard bit.
     
  7. sfsuphysics

    sfsuphysics Supporting Member

    Oh yeah? I would think that since you're basically carving you don't want to carve to fast.. *shrug* learn something new everyday :D Now if I could just rig together a drill press to put a tank under I'd be golden :D
     
  8. pixelpixi

    pixelpixi Guest

    I've had good luck using forstner bits for drilling acrylic.
     
  9. Mr. Ugly

    Mr. Ugly Past President

    Here's a good article on feeds and speeds. That's machinist talk there.

    http://en.wikipedia.org/wiki/Speeds_and_feeds

    For a 3/8" diameter drill bit, you can go 1000-1500rpm or so for acrylic.
     
  10. Mr. Ugly

    Mr. Ugly Past President

    Yah, Forstners are good because of the zero or low rake.
     
  11. pixelpixi

    pixelpixi Guest

    also I would highly recommend a drill with a torque limiter. I set mine for the lowest setting that will keep the bit moving. That way if it jams, it will stop spinning instead of splitting your piece.
     
  12. sfsuphysics

    sfsuphysics Supporting Member

    Yeah my Makita has one speed.. RAAAAAAAAAAWWWR.

    In fact I've never seen a corded drill with any torque adjustment, only seen that feature on cordless drills, I'm sure there's one out there isn't there?
     
  13. GreshamH

    GreshamH Guest

    The bits they sell for acrylic have a o degree rake, but a 90 degree point.

    http://www.craftics.com/products.cfm?Category=87

    http://www.bertram31.com/proj/tips/drill_acrylic.htm
     
  14. Gomer

    Gomer Honorary Member

    http://www.hawkfish.org/snailman/acrdrill.htm
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  15. Mr. Ugly

    Mr. Ugly Past President

    Thanks Tony.

    Yep, those are the spots to hit with a stone. Create 2 flats that are parallel to the drill bit axis.

    That website says to "dull the leading edge". Technically that is incorrect. There still needs to be a sharp edge to provide the scraping action. It's just that the included angle of the cutting edge is closer to 90 degrees after modification.
     
  16. Mr. Ugly

    Mr. Ugly Past President

    The Craftics site shows both 60 and 90 degree points.

    [​IMG]

    If you get the 60 degree point, you can be a pro :D

    Who is this Bertram guy, and why is he spreading misinformation about cutting speed? :D

    For machining, cutting, drilling acrylic, the most critical factor for the cutter is rake. Next would be relief behind the cutting edge. More relief allows you to use a more aggressive feed rate without jamming the backside of the cutter into the material to generate friction and heat. More of an issue in production than hobby applications.

    You can use a vacuum cleaner or compressed air to help remove chips and heat while machining. That keeps the chips from melting back into your material.
     
  17. Gomer

    Gomer Honorary Member

    I use a water soluble cutting fluid at work on acrylic :-D No heat issues ever!
     
  18. xcaret

    xcaret Supporting Member

    I've seen those bits at TAP plastics, what I have not seen is a countersink bit like the ones used for bubble plates on skimmers these days.
     
  19. Gomer

    Gomer Honorary Member

    can you show me a picture of the countersink you are referring to?
     
  20. xcaret

    xcaret Supporting Member

    I don't have a picture but most newer skimmers like BK, Werner, BM, etc. have the bubble plate with multiple holes bored/drilled with a countersink to reduce turbulence in the reactor chamber

    http://english.royal-exclusiv.de/Meerwasser_Aquarium/produkte/Abschaeumer-bubble-king/300mm-schaeumer-pfanne.jpg
     

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