No problem, it’s not a rush. I might get a cheap one off eBay. It’s for the router mount on my longer Z axis rail. I might try with a 6.5 in a piece of scrap alu to see if that would be large enough.
I’ve got an M8 tap, must have come with a pack of other sizes as I’ve not tapped a hole that size before. Always found it really hard to tap perfectly perpendicular to the base. I’ve never seen those combination bits before. Personally, I don’t know I’d be happy to tap using a power tool. I’d rather have the hand control and ability to stop quickly when I realise I’m not going straight!