To mount the Sizif-512 motherboard in a standard ZX Spectrum 48 case, you need to cut four additional holes: for the buttons, joystick connector, and SD card. Additionally, you need to enlarge the bottom part of the TV socket.
In the instructions, I described how to cut these holes using a template. The template has been tested on replica cases of ZX Spectrum 48 from Djordje (you can buy them here).
First, prepare the tools: two small files – a half-round and a square one with sides of 2.6-3.0 mm, a surgical scalpel, scissors, a ‘Dremel’ type rotary tool with a Φ3.0-3.1 mm milling cutter, a drill with a Φ5.5 mm drill bit, and a Φ8-12 mm drill bit.
Print the template from the PDF file below on plain paper or (preferably) self-adhesive paper. A4 sheets with self-adhesive labels in a 4 x A6 layout work well.
Remember to set the “Actual size” option when printing. This way, the printed templates will not be accidentally scaled.
From the printed sheet, cut out one set of the template with scissors. Cut the inner holes precisely with a scalpel. Screw the case together with at least three screws located closest to the back panel. Stick the template onto the case in such a way as to precisely position two points marked with red arrows in the drawing: the corner of the expansion card cutout (edge connector) and the joining point of the two case halves at the edge of the TV socket. Do not use glue! If you printed the template on a sheet of paper, use double-sided adhesive tape.
Using a ‘Dremel’ tool, slowly cut the holes in such a way as not to overheat the plastic. Grind the edges very gently, in small portions, so that the material is ground down and not “hot-pressed”. Grind the round holes for the buttons, leaving a 0.5 mm margin, which you will later enlarge with a Φ5.5 mm drill bit at low speed or manually without a drill.
Peel the paper off the case. Gently chamfer the edges of the two holes with a Φ8-12 mm drill bit. Gently grind the remaining holes with files: first the flat surfaces – with the flat part of a half-round file, and finally the corners: of the joystick and TV socket – with the half-round part of that file, and the corners of the SD card slot – with a square file.
You can gently sand larger holes with sandpaper of at least 1200 grit, attached to a round pencil or a sushi stick.
