I needed an XYZ probe for my experiments on creating pauses in an nc file to allow toolchanges to work. I haven't got around to milling aluminium yet (mainly because I haven't got any suitable aluminium) so I made mine with a piece of double-sided PCB and some square brass tube - pictures attached. I used my workbee to cut out the PCB so that I knew it was square and soldered the brass tube to the underside of the PCB. Then I connected the brass tube to the top surface of the PCB with a short wire link and soldered on the lead going to the Z limit switch (the Ooznest macro uses this to detect probe contact.) It's important that the brass tube is proud of the PCB so I soldered it flush with the edge of the PCB and then milled 0.5 mm off the edge of the PCB. Then a micrometer to check offsets so that I could adjust the macro and a crocodile clip on the other probe lead.