Thinnest Wall on Aluminum Boss for Micro Screw

[danthedesigner]

Hello,

I'm engineering a small metal housing that has very limited space. We want to use a M0.8x4mm screw to assemble the 2 CNC aluminum housing parts together. Without increasing the size of the housings we can use a boss with .03" wall thickness, not including the threads. The bosses are anchored to the perimeter wall of the housings. Are there any engineering references for designing small parts like this? Do any engineers here work on smartphones or watches? If so, could you let me know if this wall thickness will work?

Thanks!

 

[SwinnyGG]

30 thou is .76 mm.. so you have less than 1D of thread engagement.

That's not great; you typically shoot for 2D at least, after accounting for any lead in chamfer at the thread start.

Can you thicken the boss in the threaded area? Is this a formed part? Just looking at your screencap, I'm struggling to understand how the shown part could actually be machined (how are you removing material behind the flange shown)

 

[danthedesigner]

The thread engagement is 1.6mm which should be plenty. My question is focused on the wall thickness of the boss. Here is another image of the boss with the threads added.

 

[3DDave]

It's likely to be enough - it's a 1D wall so any improvement by increasing that will not be much. It certainly won't double the strength.

 

[SwinnyGG]

Ah.

I read your original post as concern about the thickness being threaded.

As far as retaining the screw, Dave is right. You have 1D all around, which should be plenty. Whether it's stiff enough for your application would be the question. Only you can answer that.. but if this is just holding a watch face on I'd imagine it's fine.

 

[danthedesigner]

Thank you for your help!