Spool Holder

My design for a quick change spool holder for to be used with M8 threaded rod. All the others that I have seen leave all the edges sharp where I have rounded them. There are recesses in both ends of what I call the bolt for a 608zz bearing. If you do not wish to use these bearings, I have designed it in such a way to also have a very small contact area so to have a small amount of friction between the holder and threaded rod.
The threads between the nut and bolt fit together snugly. I like thi