As I wanted squat condensers, I used 65mm tube. The tubes were cut to
Careful slow cutting was necessary to preserve the right angles.
Trick...to mark a pipe with a perfect 90 degree circle wrap a sheet of paper around your tube
so that the sides are perfectly parallel. Slide it to where you want to cut and go round with a marker pen where the paper meets the pipe. CLICK HERE to see how I do it
Using a drawing program I generated the template for the holes. Stuck it down with a glue stick.
Then I centre punched each mark and drilled so the tubes I used just slip through. I used 1.2mm brass plate.
Centre punch ALL holes you drill.