I have used my home built machine for years now with good results. I have 1605 Chinese rolled ballscrews (c7) on my X Y and Z axis. ( sliding bed )
( Chinese 2.2kw water cooled spindle)
Now have play in all the ballnuts, and the 20mm supported round rails on the Z and Y axis have a little play in the bearings and so does the 25mm X axis rail bearings.
So my plan is to now go square linear rail on all axis and C5 ground Ballscrews / nuts on all axis.
I am looking at used ballscrews from ebay that are ground C5

I would like to know would it be overkill to go up to a 20mm ballscrew on the Z axis (approx. 140mm of usable travel) and maybe 20mm on the other axis ? X being 400mm of travel and Y being 300mm of travel

Not sure on the size of linear square rail to go ?

I use this machine for Aluminium and want good finish and reparability without replacing everything. Hopefully I can still use the same motors



3 axis CNC/router / Alu profile frame....25mm Alu Cutting bed X=400mm Y=300mm Z=140mm.....Supported 25mm X rails (BED) ....Supported 20mm Y rails....Supported 20mm Z rails.....2.2kw Chinese WC spindle..... CSLAB CSMIO/IP-M 4-axis Ethernet Motion Controller....M542 Drivers..SY60STH86-3008BF Motors...running....Mach3 / Cambam / Emachineshop.