Is there a diy guide for making a bottomless portafilter? I tried searching a bit, but didn't find one.

Thanks

Depends on what tools you have at hand. The best solution is to use a metal lathe. I suppose if you had a lathe on hand you wouldn't be asking... So the next step is a drill press and a bi-metal hole saw. Anything beyond that is not quite so safe and/or a lot more work- as an example, a bench vise and a round file.

Since the PFs are (usually) chromed brass you will have a bi of bras showing on the cut edge. Be sure to use a fine file to clean the edge as the chrome can leave some sharp edges along the cut.

perfect thanks!