Hello; A suggestion regardless of which tool you use to cut. Put a nut or two on before the cut is done. Preferably one nut on each side of the cut. That way the nut can be helpful when it comes to cleaning up the end of the cut piece. Sometimes just unscrewing the nut can clean up the threads enough so you can put a nut back on when assembling.
I have a few oscillating tools and several blades. Would not be my first choice to cut metal rods. That said i do not have all possible blades. The closest I have are a couple which say metal/wood. I find they will eventually cut thru a nail but takes a while and quickly wears out the tiny teeth. Good chance there are dedicated blades for cutting metal, I just have not looked.
I tend to use a reciprocating saw with a dedicated thick metal blade on things such as rebar, but an old-fashioned human powered hack saw works well.
Watch out for sharp metal on the cuts. Try not to rub a finger across a sharp edge. Might use a tringle file to clean up such. Ideally having a die of the proper size and thread count cleans up the treads but a file which fits in the thread groove works.
Good luck
