These are the motor / idler ends of the x-axis for the RepRap Wilson TS 3D printer to switch from the 5mm threaded rod to 8mm 4 start leadscrew.
Here is a link to Amazon where I purchased the leadscrews used in this mod. You will also need to source some 5mm to 8mm couplers to complete the mod. https://www.amazon.com/gp/product/B017AR5QBS/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1
They are about 70mm too long, but you can get 2 for $11 while the shorter versions are charging about $7 per leadscrew.
Some caveats to these files and this setup are as follows:
I removed the Z axis adjustment screw holder on the back of the motor side. A) I never used it because it was too fiddly and inaccurate. B) It is more accurate to just have the endstop microswitch activate from the bottom of the X axis motor mount and do fine adjustment with your bed leveling.
The screw holding the X axis idler needs to have as small as a head as possible or it will hit the 8mm lead screw. I had a pretty large Phillips head screw holding the idler in and I needed to grind it down to about 1.5 - 2mm in order to get clearance from the threaded rod. I could just fit a credit card into the gap between the two.