Nozzle Change to hardened steel

Hello there. I am replacing my nozzle (going with a hardened steel 0.6mm) in a Micro Swiss all metal hot end on an Ender 3. Should the nozzle always be flush with the heater block when installed? I.e. no thread or space between the the bock and the nozzle?

You definitely want to be using hardened steel nozzles when you plan to print with abrasive filament. The way nozzles are manufactured, it’s difficult to get a smooth interior finish, with metals that are harder. It’s better to have a smooth interior to be able to extrude evenly.

welcome. usually, you want to have the inside end of the nozzle seat against the heat break before it bottoms out on the heater block to make sure there’s no gap filament can squeeze through and ooze all over everything