Compact screw bit driver with imprinted spring

Application

When you are traveling with light language, every gram of weight and every centimeter of space counts. For my motorcycle toolbox (which needs to fit under the seat) I wanted a tiny little bit screw driver. That allows me to take only a few needed bits and this tiny part with me. 

Load test results

For the bit holding head I have done tests with PETG up to 150Nm, because I had no idea how much load a plastic bit holder could take. The 150Nm was no problem at all for the part, it can probably take quite a bit more.

Model selection

Despite the imprinted spring, it is important that your bit sits well inside the holder, otherwise the holder will wear out faster. As different printers give slightly different inner diameters (talking about 0.1 to 0.2mm difference), I have uploaded two additional versions. The normal version gives a good fit on a Prusa i3 Mk3S with PETG material. The other parts, which say “slight margin” and “extra margin” in the name, gave more consistent results on a Prusa Mini. Some of my prints on the Mini did fit fine with the normal model, but some were slightly too tight. If you print on a Mini, you may want to use the model with slight margin (0.1mm wider hexagon) or extra margin (0.2mm wider hexagon).

Material selection

I strongly recommend to print this part from PETG, due to the internal tiny spring mechanism that holds the bit in place. 

Out of curiosity I have tested PLA and the internal spring broke right when I inserted the first bit. 

Printing instructions

I recommend to print this part with 100% infill, due to the high forces that might occur when you try to tighten or loosen a stuck screw. A printed with 100% infill will result in exactly 5g of weight.

I hope you find this part useful. If you do, please leave me a thumbs-up. I'd be curious to learn about your application, to see a picture of your print in action would be great!

Happy printing!