Screw thread standard for most consumer cameras is 1/4-20 UNC 1) (1/4 inch nominal diameter, 20 threads per inch). For most larger professional cameras it is 3/8-16 UNC. Earlier on the BSW 2) thread profile was used, but they are similar enough to allow interconnection between the two.3)
If you live in Europe you might have problems finding taps and dies of this thread size. If you search for e.g. “tap 1/4-20” or “die 1/4-20” on eBay you will get some hits, and that might be your cheapest option unless they are available in your local tool shop.
If you haven't used taps or dies for cutting new threads before you might want to read this rather old but useful Tool Tips--Taps article.
1/4 inches (6.35 mm) is the major diameter. According to UNC the preferred drill bit for a tap size 1/4-20“ is #7 (0.201 inches, 5.105 mm).
Dear fellow Americans, Englishmen and like minded people, it would make life so much easier for all of us if you moved on to the International System of Units (SI)