Watch makers screw bit handle

This screw driver handle combines the best of two worlds for working with small screws on our 3D printed parts. It is a small screw bit holder with an imprinted spring mechanism to hold the bit. So it lets you choose the bit insert that fits to the need of your current application. And it is small enough to fit in the palm of your hand, where it has a rotating ring that allows you to spin the handle quickly with your fingertips, while the upper end rests firmly in your hand.

Update 14.02.2021: This design is obsolete, I strongly recommend to go for Version 2.0, which is published here:
https://www.prusaprinters.org/prints/56530

Why the update? This original design did rely too much on a really clean bridging capability of your printer. The part actually prints fine on a Mk3S with Prusament PETG, but already when you try PETG from another supplier, you start to run into fitting issues with your bit. The new design is much less critical, as it prints the hex hole for the bit oriented to avoid a straight overhang. The spring mechanism now presses onto the edge of the bit, which works even better anyway.

Print instructions

Print all parts in the uploaded direction. I recommend PETG for the material, as the imprinted spring mechanism needs to be flexible.

My proposal for the infill is 100% for good strength, it is not using that much material anyway and the print time is moderate also.

Assembly:
Either cut a M3 thread into the little hole at the back side or warm up an M3 screw with a hair dryer and simply screw it in. The length of the screw is not critical, the hole is 25mm deep. I have used a M3x10. Simply put the center part into the rotating ring, put the screw in and screw everything onto the handle.

Have fun using this part and happy printing!