I am trying to source a kind of screw-heads I have seen (in tripods for example) that although you unscrew them, they do release-unscrew but they do not come out or fall. It is just as if a bit before they come out, there is something that stops them.
I cannot find their name/type even to show what I mean. Do you happen to know how can I look for them?
Usually these are some form of captive screw with retaining clip.
This PDF has a couple different types an examples.
The screw itself is normal, but has a retaining clip or nylon retainer on the back that allows it to release from its socket but not fall out. The best example I can suggest looking at is a light switch or outlet cover, they all use retaining clips so you don’t lose the tiny screws as easily.
Cyberdemon, thanks a lot for the information, much appreciated. It seems like this is what I am looking for in terms of description but in the link you sent and what I saw through my own research later on, seems like this solution needs that the retaining rings are fastened in an individual “sandwich” layer.
I contacted our MEs in Taiwan and strangely enough, they are not aware of this solution. Or perhaps something is lost in translation
I’m pretty sure you’re looking for a captive screw and captive washer.
louis, seems like this is what I was looking for. At least, by searching online “captive washers” I found videos demonstrating what I want to achieve. Cyberdemon’s suggestion seems identical but for a strange reason, by searching “Retainer clips” I could find websites/videos providing info on how the solution works.
Thanks both of you!
Here is a nice video explaining captive washers :
This post on Core reminded me of this thread;
So lest say you picked a short screw so you need a longer one but the captive washer is already crushed, how you get rid of it?
The answer for manufacturing is - you don’t ever decide a screw is short and then later try to change it. The washers are not held on by super human force, removing them usually just requires a good yank on the screw head and it will invert. The retention is usually more for convenience.
If you remove the screw completely and then try to align it with a washer thats now floating inside the housing and you can’t access it, thats another bad situation.
Of course you don’t choose short screws but mistakes happen when you have a whole machine to assemble… never saw one of these washers so I was intrigued about possible misuses and solutions.
I would expect a problem like this to be picked up by the time that you do a final phase test assembly of the machine. Its much better to spend the money on a production level proto test than to repeat fix an assembly issue 1000 times.
Right, typically there are several PP runs (pre production) to iron out those assembly kinks, not to mention DV (Design Validation) EV (Engineering Validation) runs before that. Then a short MP1 (Mass Production) before a larger MP2 run where hopefully all those things have been worked out… but… stuff still happens sometimes. I worked on a product where the factory subbed a screw out for MP2 because of availability… by the time they arrived in the U
S every product had at least one loose rattly screw. The important part about doing all those DV,EV, and PP runs is we could prove what engineering approved was not what we got. Every box was opened in MP2, every product was opened, every screw was swapped out, all in a US distribution center. An expensive fix that factory had to end up paying for.