G'day, I thought I'd quickly show you an interesting method we use for securing fasteners in laser-cut material, in this case acrylic. This base plate is ready for mounting a PCB. It's made of a few layers of acrylic to give it some substance. These four screws, they're nothing special, they just hold the stack together.

These standoffs, however, are too short to go all the way through the stack, so instead they thread into these holes. They don't thread directly into the acrylic, however, there's a captive nut that is embedded within one of the internal layers. Let's jump on the microscope and take a closer look.

We're looking at the stack from the side here, this is the top surface, here's the standoff, and we can see we have four layers, two clear layers, a black layer, and another clear. Where the standoff goes into the top layer is just a through hole for that top layer. It's in this second layer that the magic happens. You might be able to make out that there's a nut embedded there, so if I unscrew the standoff and tip the whole stack on its side, you might be able to make out, it's a little hard with clear layers involved, but you might be able to make out the edge of the laser-cut through hole, and then you can see inside the thread of a fastener. And if I get the light just right, you'll be able to see one of these facets of this laser-cut hexagon in that internal layer.

So it's a little tricky to make out, but the top layer is just a through hole, and it's in the second clear layer that there is a laser-cut hexagon to receive that nut. Just focusing on one of the fasteners, I'll take off the top layer, and you'll be able to see a bit of movement there, and there is what I usually call the nut plate. Because this is a through hexagon, this plate really does need to be kind of sandwiched between two layers, or at least have one layer on the side where the screw tension is. Otherwise, of course, this nut will just pull straight out. But if I pop this out, often only likes to come out one way. If I pop this out, you'll be able to see the hexagon is really easy to just size off. All I did was measure across the flats with some calipers and use a hexagon tool in my illustrating program.

So we used this technique when we were designing our infinity mirror kit. This is a desktop infinity mirror, which has a hollow mirror box and a control box on the back. So the problem to solve was how do we get this control box on the back of the kit without the screws coming through into the mirror box? And that was the technique we used. We embedded some nuts in the so-called nut plate, and these six screws all go down into that embedded plate. So you can have a control box that doesn't span the whole mirror and put screws through the frame, but rather just a nicer design feature where you have the protruding control box, and you can even have just two dedicated screws to take off the cover here. So that's a good example of where you might use this technique.

There you go, you can add that to your lazy cutting bag of tricks. If you like this video format where we share these little manufacturing tips, let us know and we'll keep making them. The best place of course for technical questions is on the Core Electronics forums. We're full-time makers and here to help. See you next time.