Here are my files. They are 1/2 thick, but I made them from 3/4" because the material was available, so yes, I lobbed off 1/4" not the most efficient way to make them, but you do what you need to do. The feed rates are very conservative, and I do that for several reasons. Noise (I have neighbors) and ease of manufacturing…I was building my 4-Axis while the S3 made parts unattended.
Holes. The holes are on location, but need to be opened to suit installation. I decided after I modeled the parts that I would tap out the 6mm clearance holes in the stock steel uprights to 5/16 because it will leaved the minor diameter nearly untouched. (Reason, so I can take the extensions and reassemble the machine back to its original state)
You need to drill two new holes in the uprights (using the plates as a drill jig), and I made those holes undersize, so that if there was any damage to the holes during drilling (or spot drilling) These 2 holes need to be opened to 6mm. I also countersunk the belt bracket holes (after coming off the S3) so that I could use the OEM fasteners. I have an old machine and it uses TWO 4-40 screws. Newer machines use ONE, so make the change if necessary.
PS1 I will be putting them on the machine today and will let the group (here) know if something needs to be modified.
PS2 I’m sure I forgot something, but feel free to ask.
File Links:
I named the parts Right and Left, since there are 2 different hole patterns, but that depends how you are looking at the machine…You’ll figure it out.