Summary

Ball Screw concept using a Drill Bit as the screw and roller bearings.

DISCLAIMER: This is a WORK IN PROGRESS, or better, just a CONCEPT. It is not usful for anything... yet...

Instructions

Materials

2x printed bearing holders (don't forget to configure the scad file for your Drill Bit)
4x roller bearings
4x M8 screws + nuts + washers
4x M4 screws + washers
8x nuts for M4 screws
1x Drill Bit with dual threads (I'm using a 6mm diameter SDS drill bit with 20.8mm pitch and ~1mm deep teeth)

PS.: the pitch should be measured from begining to end of the SAME thread.

Assembly

1 - Mount the bearings with M8 screws + washers + nut in the bearing holders. Mount 2 holders with 2 bearings each.
2 - Fit the 4 M4 screws with washers + nuts, in the edge holes. Put another nut + washer in each screw.
3 - Mount the 2 sides of the "ballscrew nut", with one of them "upside-down" and rotated 90 degrees (see the pictures).
4 - Insert the drill bit inside the nut. The bearings must fit in between the threads.
5 - Use the secondary nuts in the 4 screws to apply some pressure.

I don't recommend applying much pressure, the nut must run freely when the drill is in vertical position, under gravity alone.

Drill Bit Ball Screw Concept