A collet chuck for use with Chinese mini lathe. I also have some collets that will fit this chuck so be sure to check them out. The collets are ER32, so the largest supported diameter is 20mm.
I have split the chuck into 2 parts so that I don't have to support the back cavity... but if you are no keen and want to print it as a single piece... I have uploaded the whole model too.
Technical
I have printed this out of PLA, with 0.1 mm layer height 4 perimeters and 25% infill (gyroid). Not sure you need that much infill, but I am keen on the wall thickness for a bit of rigidity... The 0.1mm layer height is in support of the threads but is not strictly necessary either.