Not sure if this will help but - see the Article from Wikipedia in the attached link. There are various 'conversion tables' in there which might solve your question.
M 14 1.25
If you mean 'Screw Thread' I will give examples, but first understand that the word screw is a process. It is something you can do. We often say 'Screw these pieces together'. Now some examples :- Top of a toothpaste tube with a screw on lid. top of a jar of food with a screw on lid . A screw thread inside a water tap handle. Most common of all of course is a wood screw, and a metal thread screw or bolt.. Also the screw thread on the cap of a bottle of soft drink.
There are size on size weldolets. The hold on the run pipe will necessarily be undersize (either hot tap or torch ) because it's not possible to cut the same size hole in the run without damaging the base material.
In engineering you can use items around the workshop such as posters on info boards or their may already be drill and hole sizes for tap for example a 6.8mm drill bit for a M8 tap on a technical drawing or bend tolerences for the materials thickness.
Use 7/64 as tap drill and 9/64 as clearance drill
For a cut tap the correct drill size is a #17 drill, which has a diameter of .173 inches.
acquire correct tap from hardware or automotive supplier. Drill smaller hole through EGR port boss on head. Drill larger hole , size stated on tap to same depth as on intake port. then tap. If metric thread tap cannot be acquired a tapered pipe thread tap will also work. Threads are very close and will seal because of taper.
I use a 3/8 bit for tapping fine thread, or a 11/32 for coarse threads.
you have to remove the pressed in studs ,and tap the hole with the proper thread size for the threaded stud. this may require drilling the heads with the proper size drill, for the tap size you need. you must make sure that the new threaded studs are bigger than the pressed in ones, or you won't be able to thread the stud holes.
2,3mm
Your meaning is not clear. - If you are going to tap the threads in, use a 7/32 drill bit. If you want a hole that this bolt will slip through, use a 9/32 drill bit.
You drill the bolt out that is snapped off in the engine,with drill bit made to drill through metal. Then use a thread maker,tap. Auto parts stores carry these. I no u can get at autozone. The tap makes new threads.
Google "tap drill sizes" and you'll get 19400 results. The formula for that calculation is searchable in Machinery's Handbook, but there are simple charts you will get in your search that can give you the answer for any size you need to know.
Drill and tap it for what?
1/8, tpi=28, pitch=0.0357, major dia.=0.383, minor dia.=0.3372, tap drill size=11/32 (8.73mm)
Get a TAP the size of the CO opening