The older Necchis--Novas and Miras--fit on hinge-pins that are slightly smaller in diameter than those for Singer machines. So if you want to put a Necchi into a Singer cabinet (you will almost certainly want to do so if you're treadling your machine, given the scarcity of Necchi treadles), you'll have to either switch out the hinge-pins, or drill out the holes in the machine to fit the larger pins. My own preference is the latter; I feel it makes the machine more versatile, and you can still install it on Necchi pins, just be sure to tighten down the pin set-screws securely.
It's pretty straightforward. Get yourself a 9/32" drill bit, and mark the depth of a Singer hinge-pin on it, so you know how far to drill. I use nail polish or masking tape, and re-mark often as the drilling process tends to wear the marks off.
Set the machine on a firm surface, and prop it up so it's at an easy angle to drill straight in the existing holes. I rest the machine on some wood blocks. I also like to put paper towels under each hole to direct the flow of metal bits onto the paper and away from the works, which I have just finished cleaning and oiling. Back off the set-screws sufficiently that you won't be shortening them as you drill. Then drill until your mark is flush with the edge of the bed.
