Tru-Stone is one of the better threading materials , ebonite being the best . You must use lubrication while threading , I find Pam w/butter cooking spray works well .
I thread on the lathe with a tap and die set .
Here's an example ;
The bottom pen was made several months ago and is used allot , so far it is holding up well .
There's a technique that you have to learn but it's worth the time and trouble .