I bought a set of taps from a hardware store about 12 years ago...only one of each size from M3 to M12 with M8 & up having a few different pitches...they're mostly (haven't a clue if they're all still there) all in a rusty pile in my tool box (the partners son borrowed my tool box when I was away and left it out in the rain for a weekend :( ) I know I have M8, M6 and M4 as I've just looked but will treat myself to some new ones for my build :)

I use cutting fluid I've borrowed from work...must take it back...