This is my prototype watch movement holder that I designed a few months ago then finally got around to making. It feels solid, grips extremely well, looks great, and can accommodate very large movements when necessary (for example, I have some automotive dash clock and desk clock movements that are too large to fit commercially available holders).
Here you can see the components - the guide pins are O1 drill rod (used simply because it comes ground to a close tolerance from the supplier), the side plates are 6061 aluminum (though something like Delrin might be a better choice), the lead screw is 416 Stainless (single pointed 1/4″-28), and the jaws are also 6061 aluminum.
These last two photos show a later modification I made, to use a circlip and belleville washer instead of the compression spring. So far I’m really liking it! If you’re interested in the drawings for this tool, check out my Patreon page, at https://www.patreon.com/joyofprecision