This is intended as a tutorial for those who want to make themselves a bottomless portafilter out of a spare portafilter that they have lying around. My earlier entry on them prompted a question about how to do it, so I thought I should follow up. Obviously one should be careful when cutting things and only do it if you are comfortable and safe with the tools involved.
If you are don’t want to do it yourself you should got to Espresso Parts Northwest or antoher vendor who can sell you one or they will convert yours for you.
Lino Verna has a great reputation, too, and works for a reasonable price athttp://www.vernadesign.com/portafilter
If you have one portafilter with two spouts and one with one spout, I would use the one that has one spout, as you cannot split a shot out of a bottomless portafilter without pulling the shot and then pouring half of it in a new cup and something is always lost when a shot is poured out of a cup that it is pulled into. You might think you could pull the shot first into one cup and then switch it out for a second cup while it is being pulled, but this does not work because the taste profile of the start of a shot is not the same as the end of the shot and you will get two bad tasting shots even if the full shot was amazing.
Now the hardest trick in creating a bottomless portafilter is holding stable and securely a round portafitler with a round handle. I think the easiest way to do this is to unscrew the handle. This will reveal a bolt. Then drill a hole in a soft piece of wood (like a stud or something you might pick up at Home Depot or lowes. Make the hole the size of the bolt ignoring the threads. Then carefully screw the bolt into the soft wood. This will “tap” the hole threading it and securely. Now this block can be held in a vice or screwed into something stable.
If the handle is hard to remove blast it with heat (perhaps a heat gun or burner on a gas stove, but be careful when using heat and for that matter using power tools).
Now you need a cheap holesaw like they sell at hardware stores that goes in a drill and fits securely in the bottom of your portafilter. It should be just under the inner diameter at the bottom of the portafilter, not the quoted size of the portafilter.
Most find it easier to flip the portafilter upside down when drilling because it is easier to hld it securely that way and if you want to do this you need to unscrew the spouts off the bottom before drilling so the holesaw will fit.
Don’t worry about damaging the spout as you unscrew it because it is getting thrown away, so keep the porafilter secure and then you can use a wrench and twist it off.
Oil always helps when drilling metal, but remember this needs to be foodsafe. For that reason I skipped it last time and it worked fine, but it would have been easier with oil and would have kept the saw in better shape. Next time I think I might be tempted to try cooking oil!
It is best to sand down the cut part so it is smooth so you do not cut yourself.