PCB screws/fastner  

RE: PCB screws/fastner

I haven't done this in a very long time, so old memories at work:

Grab a self tapping screw, sheet metal cutting types are best, read the specs. There will be an optimal cutting depth and recommended hole diameter. Plan for that, and make sure the standoff plastic it threads into is at least three times the screw hole diameter. More is better, but some boards may have interference problems - back side parts, etc.   Then it's a matter of material hardness and brittleness.  A bit of trial and error "adjustment" in hole size is worth it if you plan of making a lot of parts.

RE: PCB screws/fastner

You could use heat set inserts to embed metal threads into your plastic parts so you can use machine screws. The trickiest part of this is getting the inserts to melt into the plastic straight. The Ruiz brothers of AdaFruit have collaborated with someone to come up with a jig that holds a soldering iron perpendicular to your table and guides it in a straight line to help install the inserts. Here is the link for the tutorial to build the jig: https://learn.adafruit.com/heat-set-rig

See the Developers notes section for the attribution to their collaborator. Also, while AdaFruit does sell the special heat set insert tips for soldering irons, I'm positive they aren't the sole supplier. Search around amazon, ebay, and all the other usual suspects for all the parts if you want to build it and ordering from AdaFruit is either too expensive or impractical for you.

RE: PCB screws/fastner

Yeah - Sem's post reminded me of another technology that could be adopted ... metal inserts glued in place:  once used a lot of these PEM-Nut and PEM-stud products.  Made to press into aluminum ... but might work glued into PLA.

https://www.pemnet.com/fastening-products/pem-self-clinching-fasteners-new/

RE: PCB screws/fastner

I like to use self-threading screws for use in thermoplasts. I get mine in Germany from https://de.screwerk.com/en - good thing about them is that you easily get 3D models of the screws you are planning to use.

But there are many manufacturers/distributers of those kind of screws and obviously there are different standards around the world.

Typically I design the holes with an inner diameter of roughly 93% of the nominam screw diameter and that works pretty well.

RE: PCB screws/fastner

Thanks for the replys, I think timo-m german screws are what Im looking for, will check if they have any kits.

The inserts are nice but maybe a bit of overkill for light PCBs?

RE: PCB screws/fastner

Posted by: fzherdev

Thanks for the replys, I think timo-m german screws are what Im looking for, will check if they have any kits.

The inserts are nice but maybe a bit of overkill for light PCBs?

 

Well, if you only intend on fastening the board once, sure the inserts are probably overkill. But if you have a big-honking transformer on the PCB and/or expect to install and remove the PCB somewhat frequently they might come in handy.

And, now you are aware of them just in case an application comes to mind where they would be handy. 😎 

RE: PCB screws/fastner

Exactly, thanks!

RE: PCB screws/fastner

In most of my projects, I've countersunk either a 4-40 or an M2.5 machine screw. Goes from the bottom of the case, up through the pcboard, through a spacer, into the top cover of the case, and finally a nut. 

Lately I've started to use heat-set inserts. Put them in from the underside of the case and you have plenty of room to get them in straight. I don't use any kind of a fancy jig, just my temperature controlled bench soldering iron and a steady hand. As an alternative, I did find in some instances that I could without heat just "pull" (using a machine screw and a spacer) a heat set insert into the right size hole in PETG.