This started out from me trying to use another 3d printable hex bit driver. The drill bit kept being pulled out by the piece I was making a hole in. It also couldn't handle much torque as the collet would easily spin. With that in mind while designing this driver, I added a lock that bites into the cutout at the bottom of long hex-bits and some bumps on the outside of the collet that slide into grooves in the handle to allow the user to apply more torque to whatever you're turning.

Print Settings: PETG or tougher I'd suggest printing this with settings for something that's going to take abuse. 3 walls 20% Infill Layer Height: I've only tested .28 and .2. Thicker seems like it will start running afoul of the threads.

This handle has storage in the bottom for some extra bits you may switch to often. It can also be used for long 8mm hex bits. If you want you can also print the handle grip model: print it in TPU, line it up and shove it on there. But once it's on it's designed to lock into the handle so the only way you're gonna get it off easily is by cutting it off.

The collet is keyed so it can only go in two ways. You can see in the images how it will sit higher when it's not in correctly.