If you remove the X and Y gibs, and true them on a surface grinder, you can get it down to 0.001" slop and good at end of travel. Keep well lubricated.
Cleaning them up by hand won't get it that good. Z axis is a bit more tricky due to the taper.
Until I had a surface grinder, it was difficult. You can do the Y gib using X4 as a surface grinder, locking up the Y axis with a temporary packer.
The Y axis is more critical as the axis is shorter. Put table at end of travel, and push and pull until it is almost perfect. Takes some work.
Lack of adjustments, makes it difficult to get the geometry exactly square, but then the problem becomes, how do you measure it, to be sure.
Super X3. 3600rpm. Sheridan 6"x24" Lathe + more. Three ways to fix things: The right way, the other way, and maybe your way, which is possibly a faster wrong way.