This is something have I wanted to make ever since getting my milling machine a few years ago.
The Tree mills use these unusual double taper collets to hold tools in the spindle,

They are not marked by size which is annoying, and until now I had them stored jumbled in a box in a drawer. Enter the laser!

I wanted a holder that would occupy unused space next to the machine, and have easy to read labels for the collets. The 1/4" plywood is plenty strong with a few reinforcing disks underneath.
I had a some disks that were drops out of other projects, and I just stacked them up with a pin for alignment and glued them on.

It clamps on an existing arm I added a while ago to hold the on/off switch and speed control.
I got to use the mill and lathe to make the clamp and pivot, because I love using the machines to fix/improve themselves.

The tab labels give me lots of room for big numbers, and double as finger holds for spinning to the size you want.

All in all a very successful and satisfying project!