my Cat Faucet has an IR sensor in a small plastic box which requires a small rectangular hole in the front face of the box. the below documents the best work process that I’ve been able to come up with so far for producing said small rectangular cutout.
I’ve tried using a ‘nibbler’ but the size of the required hole is too small for all the nibblers I’ve been able to find so far.
if anyone has a better way, let me know….
The first step is making a paper template and covering it with tape so that it snugly slides onto the box. It shows the 4 corners of the rectangle as well as the drill centers for the rough cutting out of the rectangle.
Using a sharp point, anything will do as long as it’s sharp. A pin, a nail, anything sharp that can withstand sufficient pressure to mark the plastic. Use that to transfer the 4 corners and drill center locations to the plastic box.
Now take a straight-edge and whatever sharp point you used to make the marks and “connect the dots” on the 4 corner marks. Does not need to be deep marks, just enough that you can see them. These will be the guidelines for actually making the hole. When you’re scribing the marks, make sure not to overrun the corner marks, this will result in scratches in the finished product.
If you run the surface with a bit of pencil lead or ever your finger, generally you can get the transferred lines to show up a bit clearer. As you continue to work the cut, these lines will be your guide, so make sure you can seem them clearly.
Here’s a trick. Drill small diameter starter holes. The amount a drill “walks” when it’s started is related to the diameter of the drill. Starting with a small diameter drill first, improves the accuracy of the location of the holes.
Now, open up the starter holes with a drill of sufficient diameter to mostly reach the edges of the rectangle. You don’t want the drill do big because there will be some variability in the drill location. Too small and you’ll have much more filing to do. Also, don’t think putting the holes closer together is a faster way to make the rectangle. If the drill holes overlap, likely the bit will just walk out of the current hole into the adjacent hole. So same with the spaces on the edges of the rectangle, close but not touching.
Use a part of cutters to remove the bulk of the material from the middle of the rectangle. This is a much more controlled way to effectively bring the drilled holes together than trying to just overlap the drill sites. Plus, if your cutters are sharp enough you can actually trim the peaks in-between the drill holes down to almost flat surfaces.
If you want, use a sharp knife (a box cutter in this case) to get the edges of the hole closer to the scribed lines. If you’d rather not work with a sharp knife that close to your fingers, just go to the next step and use the file. The knife is just a bit faster, but a little less controlled than the file.
Gently work the file side to side as you move the file back and forth. the wider the file blade, the easier it is to get straight edges. Try not to make more than one or two file strokes in the same spot, overlap them by a 1/2 or 1/4 file width. This also helps ensure straight edges. Take some off, trial fit the sensor, take some more off, trial fit and repeat. Work slowly…
It’s pretty easy to eyeball down each side to see if you indeed kept the edges straight. If they’re not, typically it’s either a slight U shape, so you’ll need to take a bit of each end, or a slight inverted U, so take off the bump in the middle. Continue trial fitting during the whole process. Once you get a corner of the sensor in, try to slide one short side up and down the length of the rectangular slot looking for places where it’s too tight and then take a bit off in that spot.