Cutter and drill for corby rivet head 6,4 mm which you can buy here:

https://nozirske-oceli.cz/corby-nyt-nerezovy-hlava-6-4/produkt

Combination drill and cutter set to precisely seat the blade to the full tang knife design. The HSS-Co5 drill has a diameter of 4.6 mm. The high-end material with added cobalt is directly designed for drilling into high-alloy and stainless steels used in knife manufacturing. The diameter of the drill bit is 0.03mm larger than the shank of a Corby rivet - 4.57mm (6.4mm head) and is used to pre-drill precise holes in the knife blade before it becomes cloudy. It is also used to drill holes in the blade. This high quality drill easily drills even tough and hard materials such as G10. Once drilled, a shank cutter is used to drill a precise hole for the head of the corby rivet. In this case 6.4 mm, which is 0.05mm larger in diameter than the rivet head. The material of the cutter is high speed steel and it also drills all commonly used materials for making shanks, including G10. The depth of the milled part of the ploughshare is secured by a stop. If everything is done correctly, it is a very precise and strong connection between the cutter and the knife.