This is a hand tool for jeweler for holding rings from the inside using an expansion mechanism.

You need :

• one 30 mm M4 round or hexagonal head screw
• one 9 mm washer if you don't have hexagonal head screw
• one M4 nut
• print one handle
• print one end cone (for hexagonal head screw or 9 mm washer and round head screw)
• print as many as you need expansion collets

I printed with a 3 mm brim, 0.3 mm layer, 2 walls and 15% cubic infil with cura slicer. In the handle and the end cones there are sacrificial bridges that allow to print without support. Once printed just break the thin sacrificial layer.

Fit the nut in the handle (might need to force it) the screw goes in the cone and the expansion collet fit on the cone. Screw in the nut you placed in the handle. When assembled fit a ring and tighten the screw, the collet should expand and lock the ring in place. Have a nice filling, sanding or engraving !