Ergonomic lockable bit screw driver with print-in-place freewheel

Use case

This screwdriver (bit holder) is made for fine to medium duty work. It is made to fit well into the palm of your hand, while still giving you a good grip for your fingers to apply some reasonable torque. 

Thanks to the clamping lock mechanism, the bits can be easily exchanged, while they are well protected against falling out during work and also allow quite a bit of torque to be applied. When printed in PETG, a moderate hand-tight lock nut should be good enough to hold the bit well. If you tighten it too much, it might be hard to unlock. 

Update 03.10.2023: Thanks to all the constructive feedback I got, I realized that the original lock-nut came out very tight with some of the used printers. Therefore I designed a nut with more mechanical play. It also features a significantly improved locking tip. I leave the original lock nut here for consistency. The new and improved lock nut can be found here:
https://www.printables.com/model/602441

To allow for quick turning of longer strews, this design also features a free-wheel at the end, that rests comfortably in the palm of your hand. 

Update 24.01.2026: I figured that depending on the used printer, the free-wheel might weld together with the handle so strongly, that I cannot be broken loose, without breaking it off completely. Therefore I designed 3 additional versions (of the regular long version), called type B, C and D. 
- the original, type A => the original design, that is a little tight on the free wheel.
- my personal favorite is type B => it breaks loose reasonable well, but is still not too loose afterwards.
- in tough cases use type C => even easier to break loose, but notable sluggish in use.
- the extreme is type D => is very easy to break loose, but quite a bit a sluggish then.

Optional variant for small hands

There are two variants of the handle, one for medium size hands and one for small hands. The version for small hands has the grip a bit closer towards the end of the handle, so it is easy to reach even with short fingers. The normal version should be good for most of you.

Printing

I recommend printing the handle and the lock nut in the uploaded orientation. No supports are needed. For the handle, I recommend to use a brim, which has helped me to never have a failed print on this part. 

In order to make the part strong, I recommend 4 perimeters and 40% infill.

I have mainly tested this design with PETG, which clearly gives superior results due to its flexibility. I have done one test-print in PLA on a Ender3Pro, which went well also. But the lock-nut needs a bit of wear-in and also needs to be tightened harder than on the PETG prints, otherwise the bit will not be held strongly. 

Your printer should not be over-extruding, otherwise the bits in the handle will become a press-fit and also the thread will not work well. If your printer is well calibrated, the thread should work quite well from the start, but of course it will run much nicer after a bit of wear-in.

Breaking free the print-in-place wheel and assembly

You will need a bit of force for the first turn of the free-wheel, but usually I manage to do that without any tools. If your printer is extruding a bit too much, you may need some pliers to rotated the wheel initially, after that it will spin nicely with a bit of wear-in.

Please like it if you like it

Your satisfaction is my reward. Please give this design a like if you like it, or post a picture of your make, that really makes my day!

Happy printing!