A couple of years ago, I got a M7x0.75 tap set (taper tap and a plug tap), as I wanted to tap the holes for a couple of potentiometers in a cast-aluminium enclosure. I found that better than making a larger hole and using a thin nut. (You can find those nuts for really cheap on eBay and Amazon, though.) I did still use the thin nuts, but this way they are just for locking, not for holding.
There are three M7 thread pitches: 0.5mm, 0.75mm, and 1.0mm. 1.0mm is the common, coarse one. 0.75mm is the fine one, used in potentiometers, rotary encoders, and some connectors. I don't know where M7x0.5 is used, but I have seen both taps and dies for it; I do believe it is called "superfine". A complete metric tap and die kit should have both M7x1.0 (in the "coarse" subset) and M7x0.75 (in the "fine" subset) taps and dies.
(M7 hex nuts and bolts also use a 11mm spanner, which is the first one you lose when you get a full set. Don't ask me why, I think the toolshed gnomes take them.)
For tapping a M7x0.75, technically you need a 6.2mm (6.188mm) diameter hole first.
Some M7 taps have a sharp enough cutting edge that they can cut the extra 0.2mm away if you are careful (and use cutting oil on thin harder materials like stainless steel), so you can start with a 6mm hole, then use the taper tap, and finish with the plug tap. Mine works fine in aluminium (i.e., I can use 6mm HSS drill bit and the end result is exactly the same as using 6.1mm drill bit, because the tap enlarges the hole) and 1-2mm thick steel. I wouldn't try it on thicker steel parts, though.
On thicker harder materials (stainless steel etc.), you should use a 6.1mm or 6.3mm drill bit, or 6mm drill then an expandable reamer or a DIY flapper (dowel or wooden rod, say 5mm in diameter, slotted, with a piece of sand paper through, so that when you rotate it in a drill, it "sands" the hole larger). Otherwise you can break the tap, which is no fun at all.