I made aluminum adapters to go from the 1/2"-20 wheel studs on the 4 in. Hard Rubber Heavy Duty Swivel Casters with Brake Harbor Freight Item #90999 to a 3/8"-16 tapped hole. The adapters are about two inches long and easily clear the the hollow casting. The mount is very solid but the assembly is top heavy and a bit tippy but still works well with the wheels locked.
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