I’m looking for options to harden an 8mm dia ball machined with a 5mm x .05 pitch threaded extension that is 23 mm long. I don’t have the ability to thread after heat treating the entire part and am concerned that a normal heat treat would damage the thread crests so am thinking of ways to just treat the ball. Any easy solutions! The material has not been chosen but can be any heat treatable material so if that helps a recommendation please advise.