[cross post from La Pavoni Lever Machine Owners fb group]

So I am about to cut a bottom in my portafilter with a hole saw.
I have 51mm hole saw that fits 49mm filter but I am not sure if I should not use 48mm instead as with 51mm I will cut slightly a piece where handle rod is mounted.
On the other hand with 48mm I am not sure if coffee will not go over the ring at the bottom of the portafilter.

Anyone tried this with 51mm hole saw on the Pre-millennium?

First of all, when I wanted a bottomless PF I purchased the convertible model from Cafelat. I only say this so you know I haven't done the hole saw conversion myself.

If it were me I would opt for keeping as much integrity where the handle attaches as possible. In my experience the coffee comes off of the bottom of the basket as a cone that is pretty much in the center. Any rim that would be left by using a slightly smaller saw shouldn't interfere with the the flow at all.

Tomasz, although you have indicated that this topic is cross-posted, we strongly discourage cross-posting on Home-Barista unless you have given time for the topic to be answered in the other forum. Your two posts went up on the same day. Here's the guideline:

Why is cross-posting strongly discouraged?

Hey Gary,

Sorry for cross post but since my experience with fb group is that either one get quick response or not at all I decided to post it also here.

I decided to invest in smaller hole saw and try 48mm first.
If I do not like the outcome I will cut the larger hole. As a matter of fact one of fb members suggested this obvious solution

One of mine portafilter is a bit bent at the rim (works well though) so I do not afraid to cut it.
I recalled that I have already made DIY bottomlesss portafilter for FrancisFrancis and then I used hole-saw of the basket/tamper diameter, i.e. 57mm.
This give me a final thought that probably 48mm will be better for pre-milenium la pavoni.

If I am happy with the result I will post a short note here.

best,
Tomasz

Tomasz,

When you have cut a 48 mm hole, if it's not quite big enough you can make it just a bit bigger if you work carefully with a file.

Either way should be fine.
The coffee does come from near the center, so outside edge does not really make a difference unless you are using a deep basket. I think on my Europiccola I found triple baskets that went so deep they could not be used in a normal pf and needed one with the bottom cut away. So, if you are happy with how much your pf holds, then smaller one is fine. If you think you might go with deeper, larger basket in the future, then use the bigger hole saw. With hole saw, once you make the cut you cannot enlarge it as nothing to hold the drill bit in the center after the cut.
Oops, I replied to an old post! Yes, file would also work...

Finally I cut my 49mm portafilter.
Just for record:
- used 48mm holesaw with a pilot drill
- I put several layers of masking tape arround the holesaw such that it tightly fit the portafilter (to make a diameter of the tool larger and ease "centering" the cut. I read that some put tape on the portafilter to protect the chrome finish. Mine was already marked by the basket so I did not care too much
- I used akku drill with low rpm
- dremel like tool for polishing the edges
- 2500 grade waterproof sand paper to polish the edge and inside of the portafilter.

Have not tried it yet but I am happy with the final result.

I just converted my premillenium portafilter as well as a MCAL one with a 1 7/8" bimetal hole saw and hand drill. Worked like a charm. First time doing something like this with metal and was surprised how easy it was. I wrapped the hole saw with many layers of masking tape to keep the bit centered instead of a pilot drill bit. I cleaned up the edges a bit with a Dremel. Mine isn't as perfect as some of the others I've seen where people polished to a mirror finish but I'm not that anal and my machines are far from perfect anyways. I just pulled a shot with the new naked portafilter on my Pavoni Pro and it worked like a treat. I was pleasantly surprised that I got a pretty good poor too!