I needed a square jack plate for my current build as it's a kind of fret-less 'sister' to my previous fretted 3 string and I want the hardware and overall style to match up. Thing is, all the commercially available square types in chrome that I could find were just a tiny bit too big. At 35.2 mm square they wouldn't fit between the very shallow corner protectors I want to use due to the depth of the 'San Cristobal Revelation' cigar box I'm using. Measuring up showed that a 32 mm square one would be just right, so decided to have a go at making one from 1.5 mm thick aluminium sheet I had on the shelf.

This pic shows the protective backing on the ali sheet marked up and punched ready for cutting. Using the jack plate on my previous build for reference, mounting holes are 3 mm with a 6 mm countersink which is 1.5 mm from the outer edge and a standard 10 mm hole in the centre. As space was tight I marked the countersink area as well, all done with a ball point pen, ruler and t square. I'll be using chrome 3 mm x 12 mm (6 mm head) scratch plate screws to mount it so I was able to employ the same 6 mm countersinking bit I use for scratch plates.

I'm sure many of you have made these before but this is my first attempt so thought I'd share it for anyone else thinking of giving it a try. The next two pics show the rest of the process, and hope it helps someone out.