In the design of this screwdriver with replaceable bits of the 6.35 mm standard, I used M6 nuts and a metal ring, this allows you to use the screwdriver applying high torque without damaging the screwdriver handle.
The metal ring is a piece of pipe 15 mm high, to make it easier to select a tube of the desired internal diameter, I publish STL files for 30, 31, 32, 33 mm.
Nuts and bits from different companies have slight differences in size, so I added STL files + (thickened bits) and ++ (thickened bits and nuts).
There are 3 options for the nuts used: 1) 12 pieces of M6 nuts; 2) 8 pieces of M6 nuts and 4 pieces of M6 bolts; 3) 4 pieces of elongated M6 nuts 15 mm long - the best choice.
Filament PETG.
Video https://youtu.be/9N69PoeBz0U