This is a related question to How to fix this in an enclosure without glueing.
However, for a protoboard/PCB, how could I attach it to the enclosure? The bottom of the enclosure has holes for attaching, but it doesn't have screw thread. How should these holes be used and how can I attach a PCB?
Glueing is not what I want, in case I want to add/change components on the protoboard later.
You buy the complementary inner panel/base plate to mount your products on.
It will fit matching the mounting holes, and it will arrive with the correct set of fasteners.
Or you could just make a PCB matching the mounting holes.
The small standoffs molded into the bottom of that plastic box can be used with the proper sized metal machine screws. The screws will cut their own thread in the soft plastic. There are several things to consider:
Figure 1. Relative size of box-top screws and PCB mounting holes.
If those are M3 screws for the lid then it looks like the mounting posts are about 3.5 mm outside diameter and maybe 1.5 mm inside diameter. You're looking for a short self-tapping screw with a 2 mm thread.
Figure 2. A selection of 2 mm self-tapping screws.
If you have a set of drill bits you can use these as a hole gauge. I use a set with 0.5 mm size increments. The screw thread should be probably about 25 to 33% larger than the hole.
I would like to offer a generic solution that I have found highly useful because it does not depend on the type of project box and does not require that the PCB have mounting holes in specific locations. This approach allows you to mount any PCB in any project box with a minimum of fuss.
1. Get (or make) standoffs tall enough to position your PCB at whatever level you prefer. My local hardware store has hollow standoffs in nylon and aluminum, but I've used wooden dowels and even drilled-out sawed-off lengths of pencil on occasion.
2. Get screws that will grab the standoffs you've chosen, and screw them through the PCB mounting holes into the standoffs. Any screws that will grab the standoffs are fine. Self-tapping sheet-metal screws are great, but sometimes an existing PCB doesn't have room for the heads on those screws, so I often use smaller machine screws. If you buy pre-threaded standoffs, obviously you need to match the screws to the threads.
3. Put your PCB (with standoffs attached) into the project box and move it around until you are happy with the position. Mark the position (or just eyeball it).
4. Get some fast-setting glue. If you want the ability to pull it apart and re-position things fairly easily, you can use a glue gun. If you want things to be really secure, use 5-minute epoxy or a 2-part polyurethane glue. If you want an instant set, use superglue with a spray accelerator. Or just use whatever you have on hand.
5. Put the glue on the bottoms of the standoffs, and put the PCB into the location you have chosen. Leave it until the glue sets.
DONE! Any PCB in any position in any enclosure.
I have a 3D printer and I print my own enclosures, but I don't bother to print standoffs any more because it's not worth the hassle to get the holes aligned perfectly with PCB holes that may not be evenly spaced. It's just too fast and easy to mount standoffs on the PCB and then glue them in place.
Hope this helps somebody!
