I'm looking for a tiny threaded collet. ER collets are fine, but you can't really use them to make long reach tooling. Shrink fit is an option I guess. My goal is to make my own mold making tool holders to use modest price proper geometry end mills in long reach applications to have greater rigidity than a long reach mill and better cost effectiveness than a tapered end mill to achieve that. I know. I know. It already exists in some types of tool holders,but I want to make something a little more universal to fit into tool holders I already have. Harvey tools makes an end mill extension, but their current version isn't tapered or designed quite right for what I want. I could buy them and maybe modify them, but they aren't cheap. Mostly I am just thinking out loud right now. I recently picked up a surface grinder, and I am making plans for making a cylinder grinding attachment for it. It would be ideal for finishing hardened tool holders like this.
Might actually use some of my grinder vises like they were intended. LOL.