Welcome to ModelEngineMaker !If you have problems registering or logging in, please use the contact menu option to request assistance.
I was in two minds about posting the build. Well, I'll post it;
All this "preparation" is to prevent issues later on. In the past, I'd picked up problems if I turned the piston to size first and then added the chamfers - they tend to slightly raise edges around them, and the piston wouldn't fit after adding the oil grooves and end chamfers. Once, on a thin-walled piston, it also "grew" in size from machining out the internal bore after first turning the outside to size.