What is the first step to cutting internal threads on an engine lathe?

zero off your workpiece so you can work from a datum, usually the centre of your work on a lathe. change your tool to a drill and drill a hole to a size smaller than your thread diameter, change out your tool for a threaded tap and away you go.

I'm not sure which part they want but I'd say ensure your tool is set to the right height, you have the tool lines up where you want to cut and that you have calculated the speed you need to cut at safety. Drill a hole before you tap though.

If you have a CNC lathe you just set the programme to do the processes and tool change for you.

explanation:

i don't understand really? can u provide more information

u should make a machine that can make ice cream fresh!