When working with small screws it's convenient to use screwdrivers that are designed to be rotated with the fingertips rather than by turning the whole hand. For this to work well the back cap of the screwdriver must be able to rotate freely.

This is my design of a 1/4'' bit driver that uses a readily available 608ZZ bearing as an end cap.

Printing

I printed the driver with 4 perimeters to make it strong.
The bit drivers in the pictures are printed with 0.2 mm layer height but other settings will work too.

Post processing

As each printer is slightly different the shaft for the bearing and the hole for the 1/4'' bit might not be perfect. It's quite easy to adjust the bearing shaft if needed:

• Oversized bearing shaft => sand until bearing fits
• Undersized bearing shaft => Add a little bit of tape around the shaft to make it thicker

The hole for the ¼ inch bit is trickier to adjust. 

• Hex hole too big => Glue a small magnet in the bottom of the hole to keep the bit in place. This might be a good idea anyway even if the hole is right to start with
• Hex hole too tight => Try making it a bit wider using a tiny file or adjust the model and reprint it with a slightly bigger hole

Customise model

You can adjust bearing shaft size, hex hole size or other features of the model by following these steps:

• Download source file (.f3d) and open it in fusion 360
• Go to “MODIFY > Chance parameters” and adjust parameters
• Save .stl file by right clicking on body > “Save as Mesh”
• There you go. Enjoy your custom bit driver model