To cut stainless steel, you want a bit or saw with a high content of cobalt, so I imagine you'd want the same for a thicker piece of steel such as would be found on a trailer tongue. I have a set of Milwaukee cobalt drill bits, and while not cheap, they cut vastly better than the typical plain steel bits.
You're probably looking for something like this:
Milwaukee Electric Tool 49-56-0173 Ice Hardened Bi-Metal Hole Saw, 3" Die, 8% Cobalt
https://www.amazon.com/Milwaukee-Ele.../dp/B0017WS1CY
...which is advertised for cutting both stainless and cast iron. Note with that particular one, the arbor is sold separately, which you would need if you don't already have one.
Dave
Threaded Mode
