This is just to share an idea or two and maybe possibly help out a fellow DIYer.
I bought this pen off of amazon https://www.amazon.c...0?ie=UTF8&psc=1
When it showed up I noticed it is very smooth and hard to hold without using a firm grip.
My solution is to add 1/2 inch heat shrink tubing to the end. I hit it with a flame and it did shrink. A few weeks later I noticed the rubber tubing moved a bit. Whatever, pushed it back in place and used a lighter again. The odd part it I had to really push the rubber on the first time before shrinking it. The tubing was just a little too small which I thought was great. Last night I noticed it moved again.
This time I took the heat shrink tubing off and applied a bit of glue. Seems good this morning but the glue needs a day or two to cure.
If I have more problems I just might take my dremel to the pen and carve some grooves around the end.
The end sometimes unscrews a few turns while it is on my belt. The pen hasn't come apart yet.
Idea #1 - Apply something to the threads so the pen is a little harder to open and close. Plumbers' tape maybe.
Idea #2 - I think it's the rubber tubing that is grabbing my clothes and turning the end of the pen. Removing the rubber and dealing with a hard to hold pen could solve the problem. Not a fan of that option.
Idea #3 - Do nothing and just get in the habit of checking the pen several times a day.
Idea #4 - Screw the end down so the ink insert is exposed - more turns before the pen comes apart.
Idea #5 - The two halves of the pen screws together with an o-ring which offers resistance to opening and closing. This could be a little thicker. Finding that could be time consuming.
Leaning towards the plumbers' tape.
Edit: the threads are completely hidden so no plumbers' tape.