We've been needing to clean up around the shop and with the plasma table taking up so much room we decided to put it on casters. This was an easy job as we cut the brackets and flanges out on the cnc plasma table and then welding everything together.
We used 1/4" bolts to combine the casters to the flanges, and used 4" casters from home depot with locking capabilities.
www.homedepot.com/p/Everbilt-...
This method could work for any metal workbench with hollow legs.
We popped the old leg levelers out and inserted the new casters.
In order to level it we will need to cut out some shims that will raise the casters up.
Our plasma table is the Langmuir Systems Crossfire Pro CNC and obviously its not an industrial grade cutter but for the price and portability this is a great plasma table.