This is my first roaster improvement project on the lathe. I had started to turn an existing (cast)
4" flange into an air control shutter index, but the existing bolt circle was so far eccentric from the OD that it never got past facing, when I realized it wasn't going to work without a lot more effort than I wanted to put into it. (Next time I think about this seriously, I'll probably do it from scratch in brass plate.)Of course, the first thing I did on the lathe was to remove the bottom of a portafilter... I'm sure it would have been quicker with a hole saw on the drill press, but there's something more satisfying about grinding a trepanning tool and doing it on the lathe.
In neither the coffee world, nor the metalworking world, would this have probably evoked more than a mild shoulder shrug... so you never heard about it, or saw pictures. ;-)
Many years ago, I made parts that ended up in reactor compartments of submarines... ground shafts to tolerances of +/-.0000" and did a lot of really amazing stuff... but what's really amazing is how much satisfaction comes from a stupid little project like this.