I have been trying to make a Hobbed bolt - It's not as easy as it looks on Youtube!
My first rig used the extruder and a failed print to mount the bearings and the bolt -
Not very good, didn't turn very well.
That seems to work much better.
Hopefully that will be good enough?
When it's assembled it seems to push well, so I just need to mount the motor and work out how to strap it onto my repstrap - then completly change all my firmware again this weekend.