Screwdriver in the end, T wrench in the middle, or in the last hole if you really need the torque. Space for 6x3mm magnets under each hole, and cut outs in the corners for a better fit.

This bit driver will work with most ¼" bits on the market, depending on which fit you print.

It is nice and compact at 75mm long, and weighs in at 10 - 15g depending on your infil choice.

I would recommend starting with the .5mm “Normal” fit version, or the "Loose" fit if you are definitely putting magnets in. The "Tight" version is good if you don't mind using pliers to remove your bits. You may have to out a bit in and take it out a few times before it eases out. If the one you print is too tight then I would recommend getting a bit in as far as you can and then heating it with a hair dryer or some heat source and then pushing it the rest of the way in with some pliers. Please don't burn youself, even hair dryers can get the bits hot!

Printing instrucions

Make sure you print this in the default orientation laying flat otherwise it will not work well at all.

I would suggest printing this with 100% concentric infil and 2 walls, once you know which fit you need, as it feels a lot nicer. A hollow version should be strong enough for most things though. The most common failure point seems to be the plastic deforming in the hole and rounding it out, so having it solid will likely not make a huge difference at that point, but can be improved by having a snug fit. I would suggest printing a hollow version with at least 15% infil, with at least 3 walls, preferably 4.

Magnets

Most 6x3mm magnets should work. The spaces under the hexagonal holes are slightly over sized so there's some room for glue. I used superglue to put mine in, but hot glue should be fine too. Make sure you use as little glue as possible, otherwise it won't just be the magnet holding your bits in place.

I have done a lot of testing and I am happy with the results, but I only have the one printer, and I'd love to get some feedback from the community, so please, let me know if you have any issues, would like different tolerances, or just think of an improvement of some sort. I have a design for a driver that works with the smaller 4mm bits, which should be on my profile soon.

Thanks!