Tightening up a thread using an o-ring?

[Danger Mouse]

I’m after some quick advice about tightening up a M10 thread on an aluminium part. I have a very nice fit up and feel except there is nothing to really hold the tightness when doing up finger tight (this is a pen barrel) and it can come lose relatively easily. I think I could just add an o-ring to give some “grip” to the two surfaces of the parts. Is the approach here to just cut a groove where my thread relief is and seat a ring so it sits just proud of the surface? Any more to it than that?
Thanks
Ian
24829B36-FD9E-4759-A4D6-6FC08A43617F.jpg

[jack620]

Is the approach here to just cut a groove where my thread relief is and seat a ring so it sits just proud of the surface?

That would work, but what's the wall thickness at the thread relief? I've made plenty of metal pens, and keeping adequate wall thickness is always an issue if you don't want the pen to be too thick.

[Danger Mouse]

That would work, but what's the wall thickness at the thread relief? I've made plenty of metal pens, and keeping adequate wall thickness is always an issue if you don't want the pen to be too thick.

Thanks Jack

The thread is M10 and the inside hole diameter for the refill is 6.3mm so probably have enough to sneak it in if I can get a nice fine o-ring.

[jack620]

...so probably have enough to sneak it in if I can get a nice fine o-ring.

Should be OK. Depends how generous you were with the thread relief cut. Would be worth measuring with callipers
and subtracting 6.35mm.

You'll also want to bore the internal thread away where it overlaps the o-ring to prevent the o-ring being chewed out. In fact, maybe just do that initially and slip a very fine o-ring over the thread relief area (no groove). The thread will prevent the o-ring sliding off when the barrel is separated.

[Danger Mouse]

You'll also want to bore the internal thread away where it overlaps the o-ring to prevent the o-ring being chewed out. In fact, maybe just do that initially and slip a very fine o-ring over the thread relief area (no groove). The thread will prevent the o-ring sliding off when the barrel is separated.

Thanks Jack