Finally I found an "off the shelf" system that works with the same casters that I bought originally for my first Makerpipe build. These inserts have a hole that was not threaded, but the insert was strong enough to withstand the strenght of the screw, and allow the creation of thread, as I was turning the screw in. I hat to hold at some point the insert with a clamp, and ended up using an english pipe wrench to be able to do the last turns to secure the caster. Now my first workshop module has weels, allows me to clean all the spaces, and works much better than my first try with the computer workstation inserts. I used also a rubber mallet to hamer the inserts into the 3/4" EMT.