JohnB. wrote:I should mention that I did this using a drill press with the p/f firmly clamped in a vise which was clamped to the press. No idea how it would go using a hand held drill.

RayJohns wrote:Drill slowly; chatter is your friend. Cutting through your portafilter with that saw is like playing the violin, not the drums. You need a little vibration in the process, to help you get through.

Also, since you are using a rather large drill there, be careful of interference and binding on the edge of the portafilter basket area. In fact, I would go so far as to apply grease to help avoid a binding situation that could cause the drill to twist and hurt you. Go. Slow; it's not a race. What you want to do is chip the brass out, more than cut the brass.

It's not like drilling a hole into a block of metal. This is more like death by a thousand tiny chips in a circle. You'll see what I mean when you start. Don't worry if it chatters and vibrates - that's just part of the process that will ultimately cut through.

I would also put tape of some sort on the outside of the portafilter, in order to protect the finish.