Page 1 of 2 12 LastLast
Results 1 to 15 of 24

Thread: How do you drill 1" holes in polycarbonate sheets

  1. #1
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    1,926

    How do you drill 1" holes in polycarbonate sheets

    I have a 1/4" thick polycarbonate sheet that I need to drill several 1" holes for makeup air in a router table window.

    I can't find any information on drilling holes that big.

    Is a hole saw acceptable? Forstner bit? Is there a special drill bit for this?
    If you drive at the speed of light, do your headlights work? - Steven Wright

    If a man points at the moon, an idiot will look at the finger.

  2. #2
    Join Date
    Feb 2004
    Location
    Perth, Australia
    Posts
    6,501
    Alan, generally the polycarbonate sheets come covered with a removable, protective film. This should prevent any chipping at the edges of the hole. If there is no film on your sheet, cover the area to be drilled with masking tape. Then simply drill. Keep the speed down, the same way you would with wood. Clear the plastic spirals as they will tangle up the bit. I use forstner bits.

    Regards from Perth

    Derek

  3. #3
    Join Date
    Mar 2003
    Location
    San Francisco, CA
    Posts
    8,676
    I've had better luck with hole saws in plastic. I've had trouble with the forstner bit grabbing upon exit.

  4. #4
    I've not tried forstner bits in PC, but have used hole saws. You need a sharp one, not one that's all beat up from other stuff. Slow rpms in a drill press, and lift often to cool the saw, otherwise you melt the stuff. If you can drill a 1/4" relief hole first, just on the inside of the cut line, it will help clear the chips.

  5. #5
    Join Date
    Mar 2003
    Location
    San Francisco, CA
    Posts
    8,676
    Quote Originally Posted by Paul F Franklin View Post
    I've not tried forstner bits in PC, but have used hole saws. You need a sharp one, not one that's all beat up from other stuff. Slow rpms in a drill press, and lift often to cool the saw, otherwise you melt the stuff. If you can drill a 1/4" relief hole first, just on the inside of the cut line, it will help clear the chips.
    Holesaws don't work well cutting straight down. There's no place for the sawdust to go, so it gets impacted in the bottom of the kerf. You're much better off if you can arrange to drill horizontally.

  6. #6
    True, but they don't work all that well horizontally either; as soon as the teeth are buried, you have the same problem. And if you're trying to get a clean hole, you need solid backing behind the piece, which is a lot easier on a drill press. That's why I recommend a relief hole or holes, whether drilling vertical or horizontal. Newer types of hole saws with relief slots are a little better, but the relief hole still works better, IMO.

  7. #7
    Join Date
    Apr 2013
    Location
    Okotoks AB
    Posts
    1,214
    Drilling holes in plastic is just about fool proof if the plastic sheet is clamped tightly between 2 pieces of wood. No chipping or grabbing. Super clean holes.

  8. #8
    The thing with plastics like polycarbonate is that they want a neutral rake angle. Brass is the same way. A positive rake angle (i.e. a normal drill bit) can cause the plastic to crack ahead of and away from the cut. For smaller drill bits you can grind a flat on the drill bit, so that the cutting edge scrapes at 90 degrees. I'd be nervous to use a forstner bit as it could grab the plastic and either pull it up the bit, shatter it, or spin it. Same thing with spade bits.

    When I did acrylic fabrication, we drilled one inch and larger holes with hole saws. The teeth on those usually don't have too much rake. Use a mix of water and dish soap to keep the holesaw cool and to lubricate the cut and carry away the chips. In the winter, we would pack snow around the hole saw. You want to back the holesaw out a couple times to clear chips as well.

    For 1/4 inch it probably isn't as critical, but on thicker pieces like 3/4 inch, if you let the hole saw can heat up too much it can expand and seize in the hole. It is important to get the plastic out of the hole saw quickly if the holesaw is hot as the holesaw can seize around the plastic as it cools.

  9. #9
    Join Date
    Nov 2006
    Location
    N.E. Ohio
    Posts
    5,602
    Andrew - you sound as though you've done quite a bit of this type thing. Would a diamond hole saw work? I keep one of those for drilling out ceramic tile and/or stone for plumbing fixtures.
    My granddad always said, :As one door closes, another opens".
    Wonderful man, terrible cabinet maker...

  10. #10
    Join Date
    Jan 2010
    Location
    Tampa Bay, FL
    Posts
    1,926
    I was wondering the same thing.

  11. #11
    Quote Originally Posted by Rich Engelhardt View Post
    Andrew - you sound as though you've done quite a bit of this type thing. Would a diamond hole saw work? I keep one of those for drilling out ceramic tile and/or stone for plumbing fixtures.
    I've never tried a diamond saw on plastic, so I don't know for certain either way. My guess is that is is going to abrade rather than shear the plastic, and may melt rather than cut if the temp gets high enough. Cutting edges in plastic, even though the rake angle is 90, still require sharpness and clearance behind the cut so that the plastic cuts cleanly and cool. Polycarbonate is fairly hard, so it may matter less whether it is sheared or abraded, but my inclination probably would be to go with a regular toothed hole saw. You could certainly try it, just make sure to keep it cool and well lubricated.

    Also, it important to have the work securely clamped and supported. Sandwiching and between two pieces of plywood as noted above isn't a bad idea, although not absolutely necessary. The main thing is that you have a lot of teeth engaged in the material, so it can transfer a fair amount of torque to the material.
    Last edited by Andrew Seemann; 08-14-2019 at 3:02 PM.

  12. #12
    Join Date
    Oct 2007
    Location
    Falls Church, VA
    Posts
    1,150
    Blog Entries
    1
    How about a step drill?

  13. #13
    I've used a hole saw on lexan to make a router base plate.

    It worked fine. Just go slow.

    To prevent burning with a hole saw, there's a great trick that I've used before with great success:

    Start the kerf with the hole saw.
    Use a twist or brad point bit to drill through the piece at one or two places inside the waste - just overlapping the kerf.
    Complete the cut with the hole saw.

    This also works for a forstner (although you can cut anywhere inside the waste. The dust relief holes make both types of bits cut remarkably efficiently.

  14. #14
    Quote Originally Posted by Prashun Patel View Post
    To prevent burning with a hole saw, there's a great trick that I've used before with great success:

    Start the kerf with the hole saw.
    Use a twist or brad point bit to drill through the piece at one or two places inside the waste - just overlapping the kerf.
    Complete the cut with the hole saw.

    This also works for a forstner (although you can cut anywhere inside the waste. The dust relief holes make both types of bits cut remarkably efficiently.
    Hi,
    I want to make sure I understand your technique.

    What exactly is the purpose of the secondary hole? Just to provide a place for waste to go?

    This sounds interesting and I will give it a try. One of my complaints with using a hole saw at a drill press is the teeth gumming up with dust and waste.
    Thanks for sharing,

  15. #15
    Join Date
    Apr 2018
    Location
    Cambridge Vermont
    Posts
    418
    The first thing you need to understand is polycarbonate and acrylic are two different beasts. Acrylic will chip where as polycarb will tear. One of the easiest ways to make multiple holes the same size would be with a plunge router with a straight bit. A simple round wood template that you can clamp onto the sheet would work well. You just want to avoid the plastic getting too hot and the material being removed removed from melting.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •