Cutting Holes in an ABS Plastic Project Box

Wrapping up a project and it is time for the case. I purchased a nice heavy duty case from Mouser to use. It needs several holes which are easy enough but it also needs a large rectangle cut out as well. In the past, cutting square holes has proven to be difficult for me.

Since you can find how to do anything on the web these days I went looking for help. Most of the procedures I saw seemed like the results were going to be rough or I simply didn’t have the necessary tools.

Then I found a tip at the end of this post:

His description was detailed and easy to follow, but I’ll toss in some pics as well.

  • I created an outline of the hole on the top of the box using a pencil and a combination square to make sure it was square.
  • I then applied masking tape leaving just the hole. In retrospect, I wish I had taped the entire box to protect it from any scratches during the cutting process. Next time…


  • Using a 1/16″ drill bit, I cut holes into each of the corners.
  • I then used a pencil to draw lines between the corners to find the center point of the hole.
  • With the center located, I drilled out a large enough hole in the center to allow a saw blade in.
  • Using an air saw, I cut from the center hole to each corner. This was the hardest part of the process – the plastic would melt and the blade would finally bind. I found that it worked better if I applied pressure for a couple of seconds, backed off, and tried again. The high speed of the saw blade probably made this worse.  Once I was done my box looked like this:


Had I used a saw or nippers, these rough cuts are what my holes normally look like which require a lot of filing and are still rough. That’s what I like about this process, the final lines are going to look way better.

  • In the picture above I have already clamped down a straight edge. I use this straight edge to run a box cutter from each end to the middle (that way the box cutter never slips and cuts the outside edge of the hole. This box is roughly 3mm thick and I probably ran the box cutter over the line 20 times to get a deep enough score cut for the next step.
  • With the outside edge of the triangle deeply scored, I then slowly bended the triangle down until it snapped off. Doing so, I ended up with a very clean outside edge:


  • Repeat the process for the other sides and you end up with a very clean hole:


  • Drilling out holes is much easier. In the past I would use a center punch to mark the center of the hole, start with a very small drill bit, then work up thru the various sizes until I got to the final diameter. Works but kind of slow.
  • This time I used the center punch, then used a step drill bit until I got to the correct size. Using this bit, the process when a lot quicker and the final hole seemed a bit smoother.
  • To finish the square hole, I just used a file. To finish the round holes, I used a deburring tool like this:

  • I bought the deburring tool on a whim and never regretted it. I’ve used it quite a few times and it is far better than trying a round file.

That’s it. I ended up with a great looking case:


I should mention that once the case was done, applied graphics to a vinyl sticker that over layed much of the top of the box. This has button labels, product name, etc on it. This is my first attempt at using such a sticker. Time will tell if it lasts very well.




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4 Responses to Cutting Holes in an ABS Plastic Project Box

  1. Pingback: Project Box Graphics | Big Dan the Blogging Man

  2. Ahmad says:

    Hi Dan
    Why don’t you use Lasercutter?!

  3. Dan TheMan says:

    They are kind of expensive so I don’t have one and I don’t know of any around here except commercial ones.

  4. Ahmad says:

    Here (Iran), we can find “Laser Cutting Services‎” in almost all towns!
    The prices is very low. For your sample the price is under 1USD!

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