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The new one is just like you mentioned; cutting boards.
Turns out it was cheapest to buy a single butcher block countertop 98" x 25", and it yielded four 24" x21" shelves.
Rods are 3/4". I considered 5/8" which are what the ones on the internet use, but they seemed a little flimsy.
I got the casters from Parts Express a long time ago. They don't have them anymore. They are mostly metal, but the wheels are plastic. They are much more durable than any I have seen lately, and they are chrome plated so they look nice enough to use on furniture.
The casters are not threaded onto the rods. There is a little trick. It's a 3/4" deep counterbore on the bottom of the lower shelf that conceals the nut, and allows you to screw the casters flat on the bottom.
My only caution if you are thinking about trying one of these shelves, and it might just my experience, but getting the shelves installed on the threaded rods is not easy!
I thought about oversizing the holes by a 16th maybe, but I was concerned it might compromise the lateral stability of the rack.