Some twenty-plus years ago, when building my spring-pole lathe, I made a terrible mistake! When cutting out the moveable puppet, I did not leave enough length on the tail to allow for a wedge. With no additional stock at the time to make another part, I decided to add a threaded dowel with which to secure the puppet in place.
Well, after years of turning this and that, not to mention the extreme changes in climate in my unplugged woodshop, it finally failed.
Luckily, while digging through my scrap bin looking for the stock to build book stands, I came upon a piece of 8/4 cherry. With just a few saw cuts and the chopping of a through mortise, I had a new movable puppet.
I do believe this version will outlive me! With a brand-new spring and puppet, perhaps I should consider a new tool rest.