Actually I wouldn't recommend building a replacement piston the way I did... it was really crap!
I ended up getting a replacement piston from the Australian distributor of the Presso. Did yours break? If you are set on making one I can email some photos/info to you.
I've been using the Presso quite a bit recently, with no modifications whatsoever (except for a bottomless PF). It is kind of funny now, but I don't think there is anything wrong with the original design... nothing that a good grinder and good coffee can't fix, that is
Thank you for the reply Henry,
Well, I am actually about to get my first Presso. The only thing that is hanging me up currently is temptation by the Truesso (you know the one), but I never found any plans for that one so I feel intimidated by trying to build one from a few pictures.
Anyways, I will probably get the Presso soon here in the USA and have a go with it. I feel confident about good results given your tutorials, but my other hardware might be lacking... my PeDe that I acquired used must have been run quite awhile misaligned because when I set the burrs to rub they do so intermittently during a revolution, so something is off eh? I could always fall back on my turkish mill that seems to rotate true and can grind to dust. And I have easy access to very good fresh roasted "Dolphin Safe" coffee from Barefoot Roasters, so that is not a problem until I start trying to roast my own!
I learned on a commercial spring-lever machine in Seattle around 1990 so I want to stay manual, but I can't even look at good spring-lever machines currently. I had a good time playing with its return action, modifying the extraction - I suppose with the Presso you can modify your pressure on the arms, in addition to altering the grind/tamp. Based on your YouTube videos I think you settled on a concave tamper, but if you have a specific model to share that would be helpful to me. Based on my reading it seems the Presso's dimensions are not standard (or is there more than one form factor?).