We needed something to drive small M4 or smaller bolts because we have hundreds of them that need to be driven. Bolts don't require a lot of torque and anything that drives them at the same speed as can be done with hand or a little faster would be a great help in terms of ergonomics.
A 9g servo converted for continuous rotation (see tutorial here) won't drive screws into wood, but is fine for small bolts we use for client projects.
To make the servo move a bit faster and to give it a tad more torque, we bumped up the voltage to 6 volts (check your servo's data sheet to see what its max voltage is) using this buck step-down power supply we picked up from Gravitech's Home of Maker.
Everything goes into the handle.
Yes we could make it cordless but this is unnecessary since all the projects this is being used for are assembled at our workbench. We wanted the handle to just fit in our hands. We did make a cordless version but it was too bulky to justify any benefits being cordless afforded it.
Check out the image below to see the evolution of the design. The big handled version on the top is the cordless version. The bottom two are earlier designs that helped determine the final design.
All the files and details on assembling this project are available on Thingiverse here.
Follow ProgressTH.org on Facebook here, Instagram here, or on Twitter here. We also put all of our 3D printed models online for free at Thingiverse.com here.
